Close Binary Speckle Interferometry

Vol. 16 No. 2 April 1, 2020 Page JournalJournal of Double Star Observations of Double Star Observations

APRIL 1, 2020

Inside this issue:

Reevaluating Double Star STF 619 105 Caroline Wiese, Alexander Jacobson, Alessandra Richardson-Beatty, Fay-Ling Laures, and Ryan Caputo

A New Double Star Detected During an Occultation by the Asteroid 4004 List’ev 113 Dave Herald

Measurements of Neglected Double Stars: November 2019 Report 116 Joseph M. Carro

Astrometric Measurements of Double-Star WDS 20437+3243(AB) 123 Don Adams, Thomas Herring, Omar Garza, and Stephen McNeil

An Astrometric Measurement and Analysis of Celestial Motion for WDS 11006-1819 131 Vladimir Bautista, Jordan Guillory, Jae Calanog, Grady Boyce, and Pat Boyce

Astrometric Measurement of WDS 13433-2458 AB 136 Roswell Roberts, Derek Chow, Kevin Lu, Marie Yokers, Pat Boyce, and Grady Boyce

Discovery of 3 New Optical Double Stars in Constellation Cygnus 139 Joerg S. Schlimmer

Double Star Measures Using the Video Drift Method - XIII 141 Richard L. Nugent and Ernest W. Iverson

Astrometry of WDS 13472-6235 148 Emily Gates, Brighton Garrett, Phoebe Corgiat, Marissa Ezzell, Jon-Paul Ewing, and Richard Harshaw A New Opportunity for Speckle Interferometry on the Mount Wilson 100-inch Telescope Rick Wasson, Reed Estrada, Chris Estrada, Richard Harshaw, Jimmy Ray, Dave Rowe, Russ Genet, 151 Rachel Freed,Pat Boyce, and Tom Meheghini Close Binary Speckle Interferometry on the 100-inch Hooker Telescope at Mount Wilson Observatory 163 Emily Gates, Audrey Hughes, Mairin McNerney, Raul Rendon, Brighton Garrett, Sara Chung, Phoebe Corgiat, Marissa Ezzell, and Jon-Paul Ewing

Astrometry of WDS 09000-4933 169 Audrey Hughes, Mairin McNerney, Sarah Chung, Raul Rendon, Jon-Paul Ewing, and Richard Harshaw Observation and Investigation of 14 Wide Common Proper Motion Doubles in the Washington Double Star Catalog Ryan Caputo, Brandon Bonifacio, Sahana Datar, Sebastian Dehnadi, Lian E, Talia Green, Krithi Koodli, 173 Elias Koubaa, Calla Marchetti, Sujay Nair, Greta Olson, Quinn Perian, Gurmehar Singh, Cindy Wang, Paige Yeung, Peyton Robertson, Elliott Chalcraft, and Kalée Tock

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 104

Inside this issue:

GAIA and CCD Observations Indicate that Herschel Double Star 10134-5054 HJ 4299 is not Gravitationally Bound 183 Karl Schmidt Counter-Check of Binaries Reported to be Detected in GAIA DR2 as Well as an Equal Mass “Twin” Binary Population 190 Wilfried R.A. Knapp

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 105

Reevaluating Double Star STF 619

Caroline Wiese, Alexander Jacobson, Alessandra Richardson-Beatty, Fay-Ling Laures, and Ryan Caputo

Stanford Online High School, Stanford, California, United States

Abstract: In 2009, Kisselev et al. proposed an orbital solution –– with a period of 490 centuries –– for the double star system STF 619. Based on the parallaxes of the stars in STF 619 according to Gaia Data Release 2, the stars are at least one parsec apart. Moreover, their relative velocity is roughly 200 times that of the system’s escape velocity. Thus, they are likely gravitationally independent. Furthermore, Scardia et al. proposed a linear solution that appears more plausible than Kisselev et al.’s orbital solution based on a polynomial Excel trendline of the unweighted historical measurements. However, because of the similarity of the linear and orbital fits over the short arc of observations, there is still uncertainty. We also made our own measurements of STF 619’s position on March 1, 2019; we found the separation and position angle to be 4.04 arcseconds ± 0.019 (1 ± SEM) and 158.5° ± 0.573 (1 ± SEM), respectively.

Introduction roughly five and 17 hours so that it would be visible in There are two types of double star systems: optical the late winter when these observations were made. and physical. Optical doubles are two stars that are Additionally, resolving the double required a separa- physically distant from one another but appear close tion of at least four arcseconds and a difference in mag- together on the celestial sphere. In contrast, the stars nitude of at most one. (The smaller the separation, the that constitute a physical double have similar distances smaller the delta magnitude had to be.) Furthermore, a from Earth and movements through space. Some physi- star with a proposed orbital solution and no fewer than cal double star systems are binary. The stars in a binary 20 previous observations –– taken over the course of at system are gravitationally bound and share a mutual least 50 years –– was desirable because it would allow orbit about their center of gravity. Based on the orbit of us to compare our observations to an existing orbital a binary star system, the combined mass of the stars solution as well as prior measurements. can be determined. This, in turn, enables astronomers Among all of the stars that satisfied the aforemen- to establish the relationships between temperature, ra- tioned conditions, STF 619 was selected. (STF 619 is dius, and mass with greater precision. also known as WDS 05013+5015 in the WDS cata- However, double star orbits may be proposed with logue and ADS 3953 in the Astrophysics Data System insufficient data, which sometimes results in optical catalogue.) The proposed orbital solution for this sys- doubles being classified as binary star systems and vice tem has a period of 490 centuries. Because the system versa. Therefore, in order to ensure accurate system has been observed for less than two centuries, more classifications, continued observation of double star observations are needed to make conclusions about this systems is crucial. star with confidence. The coordinates of STF 619 are 05H 01' 19.93" +50º 15' 25.3", placing it in Auriga. Target Selection The position of the system is shown in Figure 1, which When searching the Washington Double Star was captured using Stellarium software. STF 619 was (WDS) catalog for a double star system to study, sever- discovered by Friedrich Georg Wilhelm von Struve al restrictions had to be considered. In order to observe (1793 - 1864) in 1830. the system, it needed a right ascension (RA) between

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 106

Reevaluating Double Star STF 619

Figure 1. Position of STF 619 (indicated by white marker) relative to the constellations Auriga and Perseus.

STF 619’s Classification as Physical In his paper on the European Space Agency’s Gaia Data Release 2 (DR2), Richard Harshaw describes four factors that can be used to estimate “physicality” –– that is, the likelihood that a double star system is physically related (Harshaw, 2018). He calculated the distance between the stars, their relative proper motions, the R2 values of linear versus polynomial fits, and relative radial velocities in comparison to escape velocity. To finally estimate the system’s physicality, each factor was weighted. To be classified as a physical system, the stars must Figure 2: Kisselev et al.’s orbital solution as it appears in the WDS catalog (top) and a magnified image of the short arc of have similar parallaxes. Because the parallaxes came measurements. from Gaia DR2, Harshaw weighted this factor at 75%. A 10% weight was given to proper motion, 10% to R2 fit, and 5% to relative radial velocity analysis. After the Previous Solutions calculations and weighted factors were applied to all Kisselev et al. proposed the currently accepted or- the double stars in the WDS, the stars were sorted into bital solution for STF 619 in 2009 using the method of classes as shown in Table 1. STF 619 was categorized apparent motion parameters (Kisselev, 2009). Figure 2 as “Y?,” meaning it has 65% to 85% likelihood of be- shows his orbital solution as listed in the WDS catalog. ing physical. The green data points were measured via micrometer, Physicality Percent Number Percentage Classification Likelihood of Stars of Stars Definitely Physical > 65% 46,061 33% (Y or Y?) Maybe 50 - 65% 6,871 4.5%

?? 35 - 50% 6,613 4.5%

No < 35% 11,642 8% Insufficient Data Unknown 68,595 49% for Classification

Table 1: The number of stars in each of Harshaw’s physicality classes.

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 107

Reevaluating Double Star STF 619

Figure 3. Observations of STF 619 from 1830 – 2000. The curve corresponds to the orbital solution proposed by Kisselev et al. Figure 4. One of the images of STF 619 taken by Caputo.

and pink and blue measurements were taken, respectively, photographically and with speckle interferome- as in many refractors. While the telescope’s aperture is try. small compared to many research telescopes, there are Figure 2 shows Kisselev et al.’s orbital solution is many factors besides aperture size involved in the accu- tentative because STF 619 is a short arc binary –– that racy of images, such as mount tracking, camera noise is, only a small portion of its orbit has been observed. and seeing. Having the telescope actively operated by a The magnified image of the arc from Kisselev et al.'s person makes it easier to account for these other factors original paper is shown in Figure 3. The suggested arc (Caputo, 2019). in Figure 3 appears flipped relative to Figure 2 but this The camera used was a ZWO-ASI 1600 mm cooled is likely due to Kisselev et al.’s use of a compass rose [version 3], which uses a CMOS sensor rather than a in which North is up. CCD as in most astronomical research cameras. The In contrast, a rectilinear solution was proposed by camera has a Peltier-type cooler, which keeps the cam- Scardia et al. (Scardia, 2017). The five parameters that era at a temperature of 30° Celsius below ambient. This define Scardia et al.’s linear solution are shown in Ta- is important for imaging because an increase in temper- ble 2. The lack of consensus between the solutions pro- ature of seven to eight degrees on a CMOS sensor can posed by Kisselev et al. and Scardia et al. indicates that double the thermal noise of the image (Bracken, 2017). the nature of this double remains uncertain. The telescope mount employed was a Sky-Watcher AZ-EQ5 (shown in Figure 5). It is a German Equatorial Methods and Observations Mount design, which only tracks along one axis, rather Images of STF 619 (shown in Figure 4) were taken than two as in the case of an altazimuth mount. This by Ryan Caputo around 22:30 US Central Time on makes the telescope more precise. To track the sky March 1, 2019 (roughly day 2458544.7 of the Julian more accurately, an autoguider system was used. The calendar). An Explore Scientific ED102 apochromatic autoguider corrects small tracking errors of the mount refractor telescope with an aperture of 102 mm was by detecting motion of a preselected guide star in the used. Although the telescope’s focal length is usually guide scope and directs the mount to move a precise 714 mm, Caputo used a 2x Barlow lens, which effec- distance in the opposite direction. Since no mount can tively doubles the focal length. It has a triplet lens, indefinitely and perfectly track, the autoguide system is which reduces chromatic aberration by focusing three critical to reducing mount error. A luminance filter, wavelengths of light onto the same point instead of two which blocks infrared and ultraviolet light from enter- ing the telescope, was also part of the setup. The re- fracting telescope poorly focuses infrared and ultraviolet light, but the camera used is sensitive to such wavelengths. Thus, the luminance filter is important to re- duce chromatic aberration. Before making calculations based on the images, Table 2. A linear solution for STF 619 including five parameters the photographs were checked for saturation. Satura- proposed by Scardia et al. The final column gives the predicted position angle and separation for January 1 of 2017 and 2018. tion occurs when the photon recording capacity of a

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 108

Reevaluating Double Star STF 619

Separation Position Angle Image Number (arcseconds) (degrees) 1 4.11 160.8 2 4.08 160.2 3 4.01 157.9 4 3.99 157.4 5 4.06 157.5 6 3.99 157.4 Average 4.04 158.5 Standard Error 0.019 0.573 of the Mean

Table 3. Separation and PA of STF 619 according to an As- troImageJ analysis of Caputo’s images.

Figure 5. Caputo’s astrophotography setup, used to image Analyzing the Observations of STF 619 Using STF 619. Excel Using Richard Harshaw’s Plot Tool 2.1, STF 619’s pixel has been exceeded and thus the charge of the historical data (provided by the United States Naval freed electrons surpasses the pixel’s storage ability. All Observatory) was graphed in Microsoft Excel, as of the relevant pixels were far from saturated. shown in Figure 6. This plot of unweighted data shows The images were then platesolved using Astrome- the secondary star’s position relative to the primary, try.net. In order to calculate the separation and position which is at the origin. Our photographic measurement angle (PA) of STF 619, the star centroids were found is indicated with a red triangle. The linear trend line at using the AstroImageJ (AIJ) software’s aperture pho- the right has a marginally lower R2 value (0.8674) than tometry tool. AIJ locates the centroids by calculating a that of the second degree polynomial fit at the left weighted average of the brightness of the pixels within (0.8738). However, the fact that the polynomial trend- the area of interest. If the aperture of the photometry line curves away from the primary star suggests that tool is set too large (i.e. four pixels as opposed to STF 619 is not a binary system, because this is the op- three), either too much of the background would be in- posite of what would occur if the two stars were gravi- cluded or the other star’s light might bleed into the ap- tationally bound. erture. Therefore, setting the aperture appropriately was important. After locating the centroid of each star, AIJ Analysis of Proper Motion automatically computed the separation and PA. These The proper motion (PM) of a star is the rate of measurements are summarized in Table 3. change of its RA and declination (dec). It is usually

Figure 6: Unweighted plot of historical observations of STF 619 with second degree polynomial (left) and linear (right) trend lines. All axis scales are in arcseconds.

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 109

Reevaluating Double Star STF 619

measured in milliarcseconds of change of RA and dec over a year. In a gravitationally bound double star system, the two stars must move together through space in order to orbit each other, so the PM’s of the primary and secondary must be similar. The PM ratio (Eq. [1]

22 (PM RAprimary− PM RA secondary) +( PM Dec primary − PM Dec secondary ) PM ratio = [1] length of the longer vector between primary and secondary net PM can be used to quantify the difference in PM between two stars and determine whether or not they may be gravitationally bound. As a general rule, if the PM ratio is less than 0.2, then the two stars could be gravitationally bound. How- ever, if it is greater than 0.6, the stars are likely gravitationally independent (Harshaw, 2016). Our proper motion analysis relied on data provided by Gaia DR2, which was released in April 2018. As of the time of this study, Gaia DR2 is the most recent data and likely the most accurate. The PM values of the primary and secondary stars are summarized in Table 4. Based on Gaia DR2 and Equation 1, STF 619 has a Figure 7. PM vectors of the primary and secondary stars in STF PM ratio of 0.594. Because it is much greater than 0.2 619, based on Gaia DR2. but less than 0.6, more evidence is needed to determine whether STF 619 is a binary system. Figure 7 shows the PM vectors of the two stars. The green line represents function is approximated as (Error on D) = (Error on the PM vector of the primary; the red line represents p) * (dD/dp). Since D = 1/p, (dD/dp) = -1/p2. Therefore, that of the secondary. This figure shows that the prima- because the sign on error can only be positive, the error ry and secondary stars are moving in different direc- on D can be calculated using Equation 2: tions. The circles on the figure are several times larger than the errors on proper motion listed in Table 4, so Error on p Error on D = [2] there is no possible way for the proper motions to over- p2 lap. The errors on the distances to the two stars individ- Analysis of Parallax ually are shown in Table 5. Because it is suspected that Parallax is the angle of apparent shift of a star rela- there may be a systematic error as large as 0.1 mas with tive to background stars. Based on the parallax, the dis- Gaia parallaxes, we added 0.1 mas to the error reported tance between Earth and a celestial body can be deter- in Gaia (Luri et. al., 2018). We then used the new error mined. Using D[pc] =1 / p[a.s.] and the parallax provid- estimates to calculate the error on distance and found ed by Gaia DR2 (Table 5), the distance between Earth that the minimum possible separation of the stars is and STF 619’s component stars was calculated. around one parsec radially. It is likely that the actual In order to calculate possible error on distance, the separation in space is much larger than a parsec. How- distance (in parsecs) is expressed as a function of the ever, these parallax data do not support either a binary parallax (in arcseconds): D = f(p). The error on this or optical status due to the large uncertainty.

PM RA Error PM Dec PM Dec Error (± PM RA(mas/yr) (± mas/yr) (mas/yr) mas/yr) Primary 20.092 0.062 -29.382 0.054

Secondary -1.341 0.065 -40.991 0.056

PM Ratio 0.594

Table 4. PM values of the primary and secondary stars in STF 619.

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 110

Reevaluating Double Star STF 619

Parallax Error Distance Range of Possible Dis- Parallax (Gaia DR2) (with Revised Error) tances from Earth (mas) (± mas) (pc) (pc) Primary 4.3061 0.0372 232 ± 7.3 225-239 Secondary 4.5958 0.0375 217 ± 6.5 210-224

Table 5. Distance of STF 619’s individual components with error.

Analysis of Three-Dimensional Space Velocities xt= x o + x a  t [4] To find the relative three-dimensional space velocity, the angular proper motions are converted to linear The time in years elapsed between xt and xo is sym- motions using parallax. The relative motion vector is bolized with t. The value of x at the time of the first the square root of the sum of the star’s squared relative measurement is represented with xo; xa is the rate of motions in RA, Dec, and radial velocity. This sum is change of x as a function of time in years. Using this maximized when sum of the squared relative motions is equation with the values from Table 2, we determine maximized, as shown in Equation 3. that according to Scardia et al.’s solution, the secondary

2 2 2 star should be at (1.403487, -4.00390). According to RelativeVelocity =VVVVVVRA − RA + Dec − Dec + Radial + Radial [3] ( SPSPSP) ( ) ( ) Kisselev et al.’s ephemeris, using the interpolation tech- Therefore, to account for the error of each compo- nique described by Bush et al. (Bush et al., 2018), the nent shown in Table 6, the absolute value of each term secondary star should be at (1.336266, -3.873306) at in Equation 3 must be maximized and minimized. Us- the time of our measurement. We measured the second- ing this equation, the stars were found to have a relative ary star at (1.47969, 3.75915). velocity with a magnitude of approximately 26 km/s ± The residuals (the distance between our measure- 0.7 km/s. Since the primary star is listed in the WDS as ment and STF 619’s predicted position) were found spectral class G, and has a luminosity class V according using the formula for distance between points on a sphere: to its luminosity of 7.418 L in Gaia DR2, it can be assumed to have a mass slightly greater than that of the 22 [5] Sun. If M = 1.6 solar masses, the escape velocity of the Separation=+( dxcos d y) ( d y ) secondary at 1 pc is approximately equal to 0.12 km/s. Therefore the stars’ relative motion is more than a fac- The difference between RAs and RAp (in arcsec- tor of 200 greater than their escape velocity. onds) is notated with dx; dy symbolizes the difference Comparing Scardia’s Linear Solution to Kis- between Decs and Decp. We found our measurement to be 0.26 arcseconds away from Scardia et al.’s linear selev’s Orbital Solution prediction but only 0.18 arcseconds away from the or- At the time of our measurement, the relative posi- bital ephemeris. However, the point predicted by the tion between STF 619’s component stars as predicted Excel trend line at the right of Figure 6 is considerably by Scardia et al.’s linear solution slightly differed from closer to Scardia’s prediction than to the orbital ephem- that of Kisselev et al.’s orbital ephemeris. Scardia et eris prediction. The points are plotted in Figure 8. al.’s linear solution uses Cartesian coordinates, but Kis- Our measurement deviates from both solutions as selev et al.’s predictions are made in polar coordinates, well as the Excel trendline, with a 0.02 arcsecond SEM and had to be converted to Cartesian coordinates in or- on separation. This suggests that there is systematic der to make the comparison. In order to adhere to the error in our data. We had used only six of our clearest astronomical convention of north being down, Scardia images in this analysis, and wondered whether includ- et al.’s predictions were flipped 180°. The function ing additional images taken on the same evening would used by Scardia et al. to make their Cartesian coordi- change the result. Analyzing 17 additional images in- nate predictions is shown in Equation 4: RA Velocity Dec Velocity Radial Radial Velocity RA Velocity Dec Velocity Error Error Velocity Error Primary 22.1 ± 0.3 32.4 ± 0.4 -8.47 ± 0.57

Secondary -1.4 ± 0.1 -42.3 ± 0.4 -5.99 ± 0.56

Table 6. Linear three-component motion of STF 619’s primary and secondary stars in km/s.

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 111

Reevaluating Double Star STF 619

Figure 8. Various predictions as Cartesian coordinates in arcseconds. Historical measurements since 1950 are in black.

creased the residual from Scardia et al.’s prediction, ent. Because the PM ratio of STF 619 was between 0.2 while decreasing the residual from Kisselev et al.’s and 0.6, it is unclear from the PM ratio whether STF ephemeris. Further observation and analysis is needed 619 is a physical system. We made new measurements to determine the stars’ true trajectories. of STF 619 and found the separation and position angle to be 4.04 arcseconds and 158.5°, respectively. Alt- Future Work hough it seems that Scardia et al.’s linear solution better The Our Solar Siblings photometry pipeline was fits the past observations of STF 619 than Kisselev et used to analyze 23 of our images of STF 619. Using six al.’s orbital ephemeris, Kisselev et al.’s ephemeris bet- different photometric algorithms, this pipeline com- ter predicts the position of our observation than Scardia putes the positions (and intensities) of stars within an et al.’s linear solution. However, resolving such a close image. The DAOPhot method calculates the stars to be double is difficult and may cause our measurement to 0.084 arcseconds away from Scardia et al.’s linear solu- have relatively high error. Furthermore, it is possible tion and 0.090 arcseconds from Kisselev et al.’s ephem- that the aperture photometry we used to determine the eris (Stetson, 1987). As previously stated, the AIJ anal- centroid positions might not be optimal for such a close ysis computed the stars to be 0.26 and 0.18 arcseconds double star. The distance between the stars, the escape from Scardia et al. and Kisselev et al.’s respective pre- velocity of the system, and the Excel trendlines all dictions. Because the position according DAOPhot is strongly suggest gravitational independence. closer to both predictions, this suggests that DAOPhot is better suited for double star systems with a small sep- Acknowledgments aration. This is consistent with DAOPhot’s original This research was made possible by the Washing- purpose: photometric analysis of globular clusters with ton Double Star catalog maintained by the U.S. Naval overlapping stars. It would be valuable to further re- Observatory, the Stelledoppie catalog maintained by search the relative abilities of existing photometry algo- Gianluca Sordiglioni, Astrometry.net, AstroImageJ rithms, for this new understanding may increase the software which was written by Karen Collins and John accuracy of future analyses and therefore measure- Kielkopf, and Stellarium software by Fabien Chéreau. ments. This research also used data from the European Space Agency’s Gaia Data Release 2 (https:// Conclusions www.cosmos.esa.int/gaia), processed by the Gaia Data Kisselev et al. proposed an orbital solution with a Processing and Analysis Consortium (DPAC, https:// period of 490 centuries for the double star system STF www.cosmos.esa.int/web/gaia/dpac/consortium). Fund- 619. Based on the parallaxes, we found the minimum ing for the DPAC has been provided by national institu- distance between the component stars to be one parsec, tions, in particular, those participating in the Gaia Mul- which suggests that they are gravitationally independ-

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 112

Reevaluating Double Star STF 619

tilateral Agreement. Harshaw, Richard, 2018, “Gaia DR2 and the Washing- Special thanks to Richard Harshaw for editing our ton Double Star Catalog: A Tale of Two Data- paper as well as developing and sharing the Plot Tool bases”, Journal of Double Star Observations, 14 2.1 that allowed us to graph the historical observations. (4), 734-740. Thanks also to Bob Buchheim and Michael Fitzgerald Kisselev, A.A., J.G. Romanenko, & O.A. Kalinichenko, for assisting us with photometric analysis. Thanks also 2009, “A Dynamical Study of 12 Wide Visual Bi- to Kalée Tock for guiding us through the research pro- naries”, Astronomy Reports, 53 (2), 126-135. cess and editing our paper. Luri, X., A. G. A. Brown, L. M. Sarro, F. Arenou, C. A. References L. Bailer-Jones, A. Castro-Ginard, J. de Bruijne, T. Bracken, Charles, 2017, The Deep Sky Imaging Primer, Prusti, C. Babusiaux, and H. E. Delgado, 2018, 2nd Edition. Deep Sky Publishing. ISBN 978- “Gaia Data Release 2: Using Gaia Parallaxes”, As- 0999470909. tronomy & Astrophysics, 616, A9. Bush, Mitchell and Eric Del Medico, Hunter Boulais, Scardia, Prieur, Pansecchi, Argyle, Ling, A Ristidi, Za- Christina Lang, Jesus Escalante Segura, Sara D’am- nutta, Abe, Bendjoya, Combier-Dimur, Rivet, Sua- brosia, David Rowe, Rachel Freed, Russell Genet, rez & Vernet, 2017, “Double Stars Information Cir- 2018, “Astrometry Observations of STF 1321AB”, cular”, International Astronomical Union Commis- Journal of Double Star Observations, 14 (1), 38-42. sion on Double Stars, No. 192. Caputo, Ryan, 2019, “The Human Element: Why Ro- Stetson, P., 1987, “Daophot: A computer program for botic Telescope Networks are not always Better, crowded-field stellar photometry”, Publications of and Performing Backyard Research, Journal of the Astronomical Society of the Pacific, 99, 191– Double Star Observations, 15 (3), 408 - 415. 222. Harshaw, Richard, 2016, “CCD Measurements of 141 Proper Motion Stars: The Autumn 2015 Observing Program at the Brilliant Sky Observatory, Part 3”, Journal of Double Star Observations, 12 (4), 394 - 396.

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 113

A New Double Star Detected During an Occultation by the Asteroid 4004 List’ev

Dave Herald

Murrumbateman MPC-E07; Australia Canberra Astronomical Society (CAS) International Occultation Timing Association (IOTA) [email protected]

Abstract: An occultation of the star UCAC4 250-090193 by a small asteroid found this star to be a previously unknown double star.

Circumstances 16h 19m 32.16s, -40° 3’ 30.4”. The predicted path is On August 3, 2019 the path of an occultation of the shown in Figure 1. star UCAC4 250-090193 by the asteroid (4004) List’ev The asteroid is relatively small for occultation was predicted to pass near the author’s observatory near events. It has three diameter measurements from the Canberra, Australia. The star’s BCRS coordinates are NEOWISE project, with diameters of 24.7, 19.7±5.0,

Figure 1. Predicted occultation path

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 114

A New Double Star Detected During an Occultation by the Asteroid 4004 List’ev

Figure 2. Recorded light curve

and 16.5±4.0 km. The reduction process assumed a Figures 3 to 6 are plots for each of these solutions nominal diameter of 23 km, which equates to an angu- against the circular outline of the asteroid. lar diameter of 13.0 mas. Its rate of motion in the sky was 2.6 mas/second. Magnitudes The recorded light curve is shown in Figure 2. There is some concern about the degree of linearity The light curve shows intermediate steps at both the in the light curve. For that reason it is appropriate to start and end of the occultation. The light drop from the compare the change in light levels from the minimum intermediate step to the bottom level at the start is con- level to the intermediate levels at the start and end. This siderably greater than the corresponding rise at the end. provides light changes for the A component at the start, This indicates the sequence of occultation events was B and the B component at the end. Taking the change in -A-B-A. light level at the end being 10 units, the change at the Measurements of the durations of the occultation beginning is about 15 units. Taking these changes as events showed that component B was occulted for 4.04 being the light contributions of each component, we get secs ±0.05 sec, while component A was occulted for a total light total light of 25 units. Using the standard 4.02 ±0.07 sec. mathematical relationships for magnitudes of systems, Assuming the asteroid is circular (a big assumption this leads to the conclusion that the A component is 0.5 for a small asteroid!) there are four solutions for the mags fainter than the total magnitude, while the B com- Separation and Position Angle. They are: ponent is 1.0 mags fainter. The star is UCAC4 250-090193 = Gaia DR2 Soln Sep (mas) P.A. 5993965549837237248. The Gaia G magnitude is #1 3.2 ± 0.4 194.7° ± 11.3° 13.25. From this I conclude that the G (or V) magni- #2 7.2 ± 0.6 131.6° ± 3.4° tudes of the two components are 13.7 and 14.2. #3 3.2 ± 0.4 196.2° ± 11.4° Spatial Separation #4 7.2 ± 0.6 259.3° ± 3.4° Gaia gives the parallax of this star as 0.9852 mas.

Figure 3 Figure 4 Figure 5 Figure 6

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 115

A New Double Star Detected During an Occultation by the Asteroid 4004 List’ev

Name RA+Dec Mags PA Sep Date N Note xxxxxxx 161932-4004 13.7 14.2 195 0.0032 2019.592 1 Soln 1 xxxxxxx 161932-4004 13.7 14.2 132 0.0072 2019.592 1 Soln 2 xxxxxxx 161932-4004 13.7 14.2 259 0.0072 2019.592 1 Soln 3

Table 1. Three possible solutions for the double star

Accordingly the measured separations of 7.2mas and 3.2mas correspond to projected separations at the distance of the star of 7.3 AU and 3.3 AU. Summary The 13th magnitude star UCAC4 250-090193 is a close double star with a projected component separation of either 3 or 7 AU. Solutions 1 and 3 are essentially redundant, leaving the three possible solutions shown in Table 1.

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 116

Measurements of Neglected Double Stars: November 2019 Report

Joseph M. Carro

Cuesta College, San Luis Obispo, California

Abstract: This article presents measurements of 26 neglected double stars. The stars were selected from the Washington Double Star Catalog published by the United States Naval Obser- vatory. The photographs were taken by remote telescopes. The measurements were done by the author.

Methodology References Photographs were taken using telescopes operated Arnold, D., “Divinus Lux Observatory Bulletin Report by the Open Science Observatory located in the Canary #25”, JDSO, 8, 176, 2012. Islands near the west coast of Africa. Those telescopes are located at an elevation of 2,300 meters on the island Bertoglio, A., "Capella Observatory CCD Double Star of Tenerife. The Open Science Observatory has a cor- Measurements – Report 1", JDSO, 6, 116, 2010. rected Dall-Kirkham telescope with an aperture of Berkó, E., "Measures of Double Stars Using a DSLR 420mm, and a focal length of 2,940mm. The camera Camera #4", JDSO, 5, 189, 2009. used most frequently at the Open Sciences Observatory was a ProLine KAF-16803. The methods used to cali- Carro, J., “Measurements of Neglected Double Stars brate those instruments are unknown to this author. December 2018 Report”, JDSO, 15, 266, 2019. The photographs were analyzed by the author using GAIA DR2 data catalog as available from http:// the programs SKY X, a product of Software cdn.gea.esac.esa.int/Gaia/P Bisque.After accumulating the photographs, averages were calculated for the position angles and separations. Gulick, H., “Neglected Northern Hemisphere Binary All of the star patterns were compared with the data Stars with Updated Separations and Position An- from Washington Double Star catalog. The results are gles”, JDSO, 14, 362, 2018. listed in the table, which contain averages of measure- Knapp, W., “Measurements of WDS Objects Found in ments. Images Taken for Detecting CPM Pairs in the Report LSPM Catalog”, JDSO, 13, 553, 2017. The following information was reported for each Mason, B., Washington Double Star Catalog - Northern star: the WDS code with consstellation, the discoverer Neglected Stars List 1, 2019, http://www.astro.gsu.edu/ code with component, the position angle, the separa- wds/Webtextfiles/neglected_list1.txt. tion, the number of measurements, and the date of the Nugent, R., "Double Star Measures Using the Video last observation. Drift Method - VII”, JDSO, 12, 511. The column headings are: WDS number/Con = Washington Double Star identifier/Constellation code, Nugent, R., "Double Star Measures Using the Video DC = Discovery Code and components, PA = position Drift Method - VI", JDSO, 11, 117, 2015. angle, Sep = Separation, Mts = number of measure- OAG Catalog as published by the Washington Double ments, and Date = the last observation date. Star website, 2019, http://www.astro.gsu.edu/wds/ Acknowledgements unpublished/oag.html. This research made use of the SIMBAD database Tycho-2 Catalog as published on their website, 2019, operated at CDS, Strasbourg, France, the Aladin Sky https://www.astro.ku.dk/~erik/Tycho-2/. Atlas, and the Washington Double Star Catalog maintained by the United States Naval Observatory. Vollman, W., “Double Star Astrometry with a Simple CCD Camera”, JDSO, 4, 128, 2008.

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 117

Measurements of Neglected Double Stars: November 2019 Report

WDS/ Con DC/Com PA Sep Mts Date

00014+4758 And TDS 1250 AB 288.71 1.1 4 2019.7616

Tycho 2 290 0.99 1991.77

WDS 290 1.0 1 1991

WDS/ Con DC/Com PA Sep Mts Date

00027+3433 And TDS 1266 AB 143.86 0.6 4 2019.7616

Tycho 2 143 0.54 1991.58

WDS 143 0.5 1 1991

WDS/ Con DC/Com PA Sep Mts Date

00066+2901 And STT 549 AB 260.05 193.6 2 2019.7616

JDSO (Arnold) 258.8 187.63 2012

Tycho 2 257.9 184.6 1991.6

WDS 260 192.5 21 2015

00066+2901 And ENG 1 A,CD 200.34 139.7 2 2019.7616

WDS 200 141.9 14 2013

00066+2901 And BU 1338 CD 210.70 3.3 2 2019.7616

GAIA DR2 210.26 3.15 2018

WDS 210 3.1 13 2015

WDS/ Con DC/Com PA Sep Mts Date

00066+4503 And TDS 1297 AB 21.23 1.9 3 2019.7616

GAIA DR2 19.31 1.97 2018

Tycho 2 24 2.03 1991.62

WDS 19 2.0 2 2015

WDS/ Con DC/Com PA Sep Mts Date

05499+2259 Tau POU 789 AB 251.21 12.4 3 2019.6055

JDSO (Gulick) 251.3 12.7 2016

WDS 251 12.7 14 2017

05499+2259 Tau ARN 91 AC 132.12 112.4 3 2019.6055

WDS 132 112.0 13 2015

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 118

Measurements of Neglected Double Stars: November 2019 Report

WDS/ Con DC/Com PA Sep Mts Date

07453-0026 Mon HJ 767 AB 163.98 21.2 3 2019.7014

JDSO (Arnold) 163.8 22.22 2007.915

JDSO (Carro) 163.33 214.3 3 2018

JDSO (Nugent) 163.08 20.8 2016.173

WDS 163 20.8 15 2016

07453-0026 Mon SIN 31 AE 27.70 27.8 3 2019.7014

WDS 27 28.4 6 2016

07453-0026 Mon SIN 31 AG 164.16 31.6 3 2019.7014

WDS 164 31.4 1 1989

07453-0026 Mon SIN 31 AI 359.74 107.1 3 2019.7014

WDS 1 107.5 1 1989

07453-0026 Mon SIN 31 AJ 73.48 169.3 3 2019.7014

WDS 74 168.8 4 2015

07453-0026 Mon SIN 31 AK 63.86 179.7 3 2019.7014

WDS 65 179.4 1 1989

WDS/ Con DC/Com PA Sep Mts Date

18436+1207 Her HJ 1338 AB 189.27 11.5 3 2019.6055

GAIA DR2 189.65 11.50 2018

WDS 190 11.5 15 2015

WDS/ Con DC/Com PA Sep Mts Date

20161+1537 Del CHE 255 AB 216.44 24.6 3 2019.6055

JDSO (Berkó) 212.27 10.51 2008.773

WDS 212 25.5 5 2008

WDS/ Con DC/Com PA Sep Mts Date

20171+1604 Del CHE 270 AB 102.86 16.1 3 2019.6740

GAIA DR2 102.87 15.9 2018

JDSO (Berkó) 103.01 15.87 2008.773

WDS 103 15.9 11 2015

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 119

Measurements of Neglected Double Stars: November 2019 Report

WDS/ Con DC/Com PA Sep Mts Date

20172+0504 Aql BAL 2965 AB 134.24 17.3 3 2019.6055

GAIA DR2 103.24 14.35 2018

WDS 103 14.4 7 2015

WDS/ Con DC/Com PA Sep Mts Date

20173+1443 Del CHE 275 AB 332.13 30.4 3 2019.6055

JDSO (Berkó) 330.04 31.54 2008.778

WDS 330 31.5 11 2015

WDS/ Con DC/Com PA Sep Mts Date

20177+2025 Sgr J 2308 AB 282.72 37.0 3 2019.6055

JDSO (Bertoglio) 281.9 37.8 2007.5729

WDS 282 37.0 6 2015

20177+2025 Sgr J 2308 AC 283.89 42.5 3 2019.6055

JDSO (Bertoglio) 283.8 42.6 2007.5729

WDS 284 42.7 5 2015

20177+2025 Sgr J 2308 BC 296.51 5.7 3 2019.6055

JDSO (Bertoglio) 296.1 5.67 2007.5729

WDS 297 5.7 9 2013

WDS/ Con DC/Com PA Sep Mts Date

20181+1519 Del CHE 290 AB 153.41 10.2 3 2019.6055

GAIA DR2 153.41 10.15 2018

JDSO (Berkó) 153.93 10.06 2008.778

WDS 153 10.1 11 2015

WDS/ Con DC/Com PA Sep Mts Date

20183+1539 Del CHE 293 AB 353.93 24.8 3 2019.6740

GAIA DR2 354.25 25.02 2018

OAG (Tobal) 174.1* 24.79 1982.559

JDSO (Berkó) 174.02* 25.06 2008.773

WDS 354 25.0 12 2015

If 180º is added to the values marked with an *, those values will be consistent with the WDS.

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 120

Measurements of Neglected Double Stars: November 2019 Report

WDS/ Con DC/Com PA Sep Mts Date

20186+1444 Del CHE 296 AB 23.40 28.2 3 2019.6055

GAIA DR2 23.83 29.64 2018

OAG (Tobal) 23.3 28.29 1982.559

JDSO (Berkó) 23.69 29.50 2008.778

JDSO (Knapp) 23.819 29.634 2017.304

WDS 24 29.6 13 2016

WDS/ Con DC/Com PA Sep Mts Date

20186+1548 Del CHE 295 AB 259.70 13.6 3 2019.6055

GAIA DR2 259.08 13.55 2018

OAG (Tobal) 263.2 16.13 1984.512

JDSO (Berkó) 259.89 13.69 2008.778

WDS 259 13.6 10 2015

WDS/ Con DC/Com PA Sep Mts Date

20187+1551 Del CHE 298 AC 137.70* 16.9 3 2019.6740

GAIA DR2 317.69 16.75 2018

OAG (Tobal) 137.1* 16.82 1984.512

JDSO (Berkó) 137.52* 16.71 2008.778

WDS 318 16.8 7 2016

If 180º is added to the values marked with an *, those values will be consistent with the WDS.

WDS/ Con DC/Com PA Sep Mts Date

20188+1530 Del TOB 319 AB 64.77 14.9 3 2019.6746

OAG (Tobal) 59.2 15.4 1984

JDSO (Berkó) 65.27 15.12 2008.778

WDS 65 15.0 9 2015

20188+1530 Del CHE 299 AC 329.37 37.6 3 2019.6746

JDSO (Berkó) 328.84 37.21 2008.778

WDS 329 37.1 10 2015

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 121

Measurements of Neglected Double Stars: November 2019 Report

WDS/ Con DC/Com PA Sep Mts Date

20189+1546 Del CHE 301 AB 295.51 28.1 3 2019.6740

GAIA DR2 295.92 27.6 2018

OAG (Tobal) 295.4 27.57 1984.682

JDSO (Berkó) 295.71 27.91 2008.778

WDS 296 27.8 12 2015

WDS/ Con DC/Com PA Sep Mts Date

20247+1443 Del HJ 1508 AB 59.23 13.9 3 2019.6740

GAIA DR2 58.12 13.8 2018

OAG (Tobal) 57.7 13.54 1982.559

JDSO (Vollman) 58.72 13.57 2006.697

WDS 59 13.8 7 2016

20247+1443 Del VLM 4 AC 152.25 17.4 3 2019.6740

GAIA DR2 152.29 13.8 2018

JDSO (Vollman) 153.31 13.83 2006.697

WDS 153 17.4 9 2016

WDS/ Con DC/Com PA Sep Mts Date

20358+0508 Del BAL 2968 AB 10.32 13.9 3 2019.6876

GAIA DR2 10.90 13.6 2018

WDS 11 13.5 11 2015

WDS/ Con DC/Com PA Sep Mts Date

20484-1812 Cap S 763 AB 293.48 15.8 3 2019.6520

GAIA DR2 293.76 15.55 2018

OAG (Tobal) 298.5 16.44 1992

JDSO (Arnold) 293.4 15.80 2012.577

Tycho 2 293.8 15.6 1991.54

WDS 293 15.8 44 2016

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 122

Measurements of Neglected Double Stars: November 2019 Report

WDS/ Con DC/Com PA Sep Mts Date

21080+1338 Del SLE 529 AB 345.28 8.1 3 2019.6740

GAIA DR2 345.40 7.96 2018

WDS 345 8.9 10 2015

WDS/ Con DC/Com PA Sep Mts Date

21167+2819 Vul MLB 574 AB 333.71 7.7 3 2019.6740

GAIA DR2 333.12 7.35 2018

WDS 333 7.4 9 2015

WDS/ Con DC/Com PA Sep Mts Date

22069+3335 Peg ES 385 AC 0.4 33.3 3 2019.6740

WDS 0 33.0 7 2015

22069+3335 Peg TOB 225 AD 6.87 122.1 2019.6740

OAG (Tobal) 6.4 122.3 1982

WDS 7 121.8 9 2015

WDS/ Con DC/Com PA Sep Mts Date

23232+1226 Peg HJ 3188 AB 252.75 21.7 3 2019.6740

GAIA DR2 252.76 21.94 2018

JDSO (Nugent) 252.4 21.9 2014.805

Tycho 2 252.3 21.74 1991.61

WDS 253 21.9 16 2015

23232+1226 Peg BU 1529 AC 264.08 126.9 3 2019.6740

WDS 257 126.9 4 2011

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 123

Astrometric Measurements of Double-Star WDS 20437+3243(AB)

Don Adams1, Thomas Herring1,2, Omar Garza1, Stephen McNeil3

1 Jack C Davis Observatory (JCDO), Carson City, NV 2 Western Nevada College, Carson City, NV 3 Brigham Young University-Idaho, Rexburg, ID

Abstract: .Separation and position angle measurements were made for the double star WDS 20437+3243(AB) using two instruments and two methods for extracting data. The results were compa- rable for both instruments and methods. Separation was 7.50 arc seconds and the position angle was 123.6 degrees. These results were compared to the historical data and in conjunction with our data we can only say that the nature of these double stars remains “uncertain”.

Introduction 20437+3243(AB) in the constellation Cygnus using two This work was undertaken as part of the Astronomy different instruments, one at the Jack C Davis Observa- Research Seminar which provides practical experience tory (JCDO) and the other from the Las Cumbres Ob- in astronomical research and an understanding of the servatory (LCO) network. The results were compared nature of scientific research. The goal of the program is using multiple images and measurements from each. to expose high school and undergraduate college stu- An additional experiment was done in which the JCDO dents to research projects early in their education images were stacked using two different methods. A (Genet). The study of double stars with small tele- single measurement from each of the stacked images scopes is within the reach of students given the time was made for comparison. they can devote to such a project and availability of Equipment and Methods equipment. At the same time their work provides an This target was selected as a “neglected” double additional source of valuable data for the scientific from the Washington Double Star Catalog that was community. The authors intend to offer this opportuni- downloaded into an Excel worksheet. The criteria used ty as courses available to undergraduates at their re- to select this double star was that the magnitude of the spective institutions. In addition the Jack C Davis Ob- primary star should be between 7 and 11 with separa- servatory will offer training in performing double star tion between 5 and 9 arc seconds and delta magnitude astrometry to interested members of the Western Neva- less than 3 so that the measurements could be made da Astronomical Society (WNAS). By taking part in the with the 0.4 meter telescopes available to us. It should fall 2019 Astronomy Research Seminar (ARS) Western also be visible in the night sky in October when meas- US, offered by Rachel Freed at Sonoma State Universi- urements were made which limited RA between 18 and ty, the authors are gaining skills in double star astrome- 8 hours. To qualify as ‘neglected’ we further limited try, associated data analysis, and insight into the learner our choice to between 4 and 10 measurements with the experience in double star research. The future offerings most recent no later than 2008. Ideally we also looked at these institutions will provide research experience for for measurements that spanned many years so that add- a variety of learners and help to grow the community of ing ours might tip the scales one way or the other in double star researchers. determining whether it is a gravitationally bound bina- This paper describes the measurement of separation and position angle made for the double star WDS (Text continues on page 124)

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 124

Astrometric Measurements of Double-Star WDS 20437+3243(AB)

used. Corresponding dark, flat and bias images were taken for image processing and calibration with Maxim DL 6. The images were then plate solved for astrometric data extraction with AstroImageJ. The images were also stacked with Maxim DL 6 using an average algorithm and a median algorithm from which the same data was extracted using AstroImageJ. Results The collected images were analyzed with As- troImageJ to determine the separation (Sep) in arc seconds and the position angle (PA) measured from North towards East in degrees. These results are summarized in Tables 1 and 2. Table 3 shows the results for stack-

ing images. Figure 1. JDCO Telescope, a) Takahashi c400 and b) authors Tom Herring and Omar Garza at the controls. The images in Figures 2 and 3 are from As- troImageJ for the LCO and JCDO. Each is a single reduced image from which astrometric measurements ry. The first measurement for the selected star was in were made. Figures 4 and 5 are images for the stacked 1929 (Espin) and the most recent was in 2002. As a JCDO images using the average and median method, result of our secondary goal for the JCDO we further respectively. These were then used to make a single limited candidates to the northern hemisphere and re- measurement for each method as summarized in Table duced the RA range. The selected star was easily seen 3. Figure 6 is a wider field of view centered on the tar- from this site in Carson City, NV, given the clear skies get system from the LCO images. By comparison, Fig- experienced there in October 2019. ure 7 is an image from Stelladoppie.it. CCD images were acquired by multiple 0.4 meter We compared our measurements with historical telescopes from the Las Cumbres Observatory (LCO) WDS data which is summarized in Table 4. GAIA network. These are modified Meade telescopes with DR2 data from 2015 was used to calculate the separa- custom equatorial mounts and high-quality SBIG STL- tion and position angle (Gaia Collaboration et al 2016 6303 cameras. All hardware and control software is and 2018b) on that date. Our measurements are includ- identical. Complementary measurements were also tak- ed at the end of the table. This data is plotted in Figure en at the Jack C Davis Observatory (JCDO) with a 0.4 8a and 8b relative to the primary star (A). Each data meter Takahashi c400 Cassegrain telescope (focal # length 5600 mm) and an SBIG STL1001 camera. See LCO Results Average StdDev Std Err Figure 1. This system is equipped with The SkyX samples Planetarium software, a Paramount ME equatorial Sep (as) 7.55 0.018 10 0.006 mount (both by Software Bisque for scope control), and PA (deg) 123.9 0.2 10 0.06 Maxim DL 6 (for camera control). LCO settings and image processing: Table 1. Summary of astrometric data extracted from LCO images. Ten images were acquired at exposure times of 1, 2 # sam- JCDO Results Average StdDev Std Err and 4 seconds from the LCO network. All were taken ples with a clear or air filter and processed by the LCO data Sep (as) 7.44 0.14 20 0.03 pipeline called BANZAI. The best of these were 2 second exposures taken at the Teide Observatory on Tene- PA (deg) 123.4 0.75 20 0.17 rife in the Canary Islands and 4 second exposures taken at the McDonald Observatory in Texas. The latter 4 Table 2. Summary of astrometric data extracted from JCDO images. second exposures had SNRs greater than 40 dB and JCDO Stacked By Averaging By Median were therefore used to extract astrometric data with Results AstroImageJ (AIJ). Sep (as) 7.4 7.4 JCDO settings and image processing: Twenty images were acquired using a 4 second PA (deg) 123.2 123.1 exposure time at the JCDO after some experimenting Table 3. Summary of astrometric data using stacked JCDO images. and inputs from the LCO results. A clear filter was (Text continues on page 129)

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 125

Astrometric Measurements of Double-Star WDS 20437+3243(AB)

Figure 2. Single reduced image from the LCO data set.

Figure 3. Single reduced image from the JCDO data set.

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 126

Astrometric Measurements of Double-Star WDS 20437+3243(AB)

Figure 4. Stacked image using the averaging method from the JCDO data set.

Figure 5. Stacked image using the median method from the JCDO data set.

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 127

Astrometric Measurements of Double-Star WDS 20437+3243(AB)

Figure 6. Wider view from an LCO image. WDS 20437+3243 is at the center.

Figure 7. WDS 20437+3243 ES 2376AB : Aladin DSS image @ 20h 43m 44.64s +32° 42' 35.4", FOV = 12.05’. Image from Stelladoppie.it.

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 128

Astrometric Measurements of Double-Star WDS 20437+3243(AB)

Figure 8a. Plot of historical data with our most recent measurement. The dotted line is a regression on the data including the primary star at the origin.

Figure 8b. Plot of historical data with expanded scales that more clearly show the range and sequence of measurements over 90 years.

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 129

Astrometric Measurements of Double-Star WDS 20437+3243(AB)

Date PA Sep aperature # Obs. Disc. Code 1929.82 124 6.74 0.6 2 Es_1930 1930.86 121.2 7.41 0.3 1 WFC1998 1934.83 125.6 7.64 0.3 1 WFC1998 1998.76 123.6 7.75 1.3 1 TMA2003 2002.57 125.0 7.63 0.2 5 UC_2013b Eu 2015.50 126.4 7.50 GAIA DR2 2019.82 123.89 7.55 0.4 LCO 2019.82 123.42 7.44 0.4 JCDO

Table 4. Historical data from the WDS catalog. The 2015 entry is calculated using GAIA DR2 data. The last two entries are our measurements from Tables 1 and 2.

(Continued from page 124) is odd they are traveling through space at about the point is labeled since there are only eight. A linear re- same distance, and with about the same proper motion. gression line is shown that includes the primary star at Since the AB components of the system are separated the origin. This should be the major axis of an elliptical by less than the 200,000 AU criteria suggested by orbit if these stars are gravitationally bound. Note that Knapp (Knapp 2018 and a recent JDSO submission) there is no estimated orbit for this system in the 6th this is further evidence it is probably physical. Howev- Orbit Catalog. er, the small masses and large orbital period make con- firmation difficult given measurements over just 90 Discussion years. It is no wonder the data look like random meas- Our most recent data appears to show no relative urement error. It may be possible to use our data and motion between the AB stars in this double system. In future measurements, in the distant future, to resolve fact one could argue that the scatter in the measure- the status of this enigmatic system. ments reflects measurement error. However, Richard It is possible that we are viewing this double star Harshaw recently did a survey of the WDS catalog system on edge such that the semi-major axis is small. were he combined it with GAIA DR2 (Harshaw 2018) If the secondary star is near a focus/vertex of the ellipse using ‘physicality’ metrics he defined. He defined (apastron) the observed data would be bunched up as ‘physicality’ as “the likelihood that a given pair is trav- we have observed. In this case it may take much more eling together through space, may have a common than 90 years before an orbit is revealed, especially if origin, and may, in fact, be in orbit around a common the orbital period is almost 200,000 years. center of gravity.” From the worksheet he created this We successfully made measurements of the AB system is classified Y or ‘definitely physical’. See Ta- components of this system. While doing our research ble 5 for an excerpt from that table. Our independent we learned there is a third star in it, AaAb, with much calculations using the GAIA DR2 data indicate the dis- smaller separation reported at as little as 1.3 arc sec- tance to the AB components is 664 ± 17 and 661 ± 14 onds. The images from both the LCO network and at parsecs. Since the distances overlap considerably, and JCDO reveal this star as elongation of the primary A if we assume they are really at the same distance, then component but could not be resolved. It is possible this with an angular separation of 7.5 arc seconds this gives could affect the accuracy of AB component measure- a separation of 4980 - 5110 AU. The observed GAIA ments since the centroid of the A star is less certain and effective temperatures and luminosities place both stars could even be moving. on the main sequence of the H-R diagram. Using the Similar results were obtained with the JCDO and mass-luminosity relationship for main sequence stars LCO network instruments but the variation in JCDO the estimated masses are roughly 2.1 and 1.3 solar measurements is larger as reflected in the standard de- masses. Using Kepler’s Third Law these masses give viations. It is likely this difference is a result of differ- an orbital period of roughly 192,000 - 200,000 years. It ences in the size and number of imager pixels for the

Table 5. Excerpt from Harshaw’s worksheet with entries for the WDS 20437+3243 system.

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 130

Astrometric Measurements of Double-Star WDS 20437+3243(AB)

cameras used. Both telescopes had the same aperture, www.cosmos.esa.int/web/gaia/dpac/consortium). Fund- 0.4 meters. The camera at the LCO has 3072x2048 9 ing for the DPAC has been provided by national institu- um square pixels whereas at the JCDO has 1024x1024 tions, in particular the institutions participating in the 24 μm pixels. This results in spatial resolution of Gaia Multilateral Agreement. We would also like to 0.571" and 0.884" respectively. The lower resolution thank Rachel Freed at Sonoma State University for her of the JCDO camera will result in more sampling noise guidance and work to organize the Astronomy Re- as observed. Nonetheless, the JCDO equipment is ca- search Seminar. Finally we’d like to thank Richard pable of doing this type of precise measurement for Harshaw for providing suggestions to improve this pa- double star research. There is slightly better agreement per. between the PA measurements. The stacking method using the JCDO images also yielded similar results but References does not allow for an estimate of variation. In this case Espin, T. E.; Milburn, W.; “Micrometrical Measures of stacking did not result in any gains of the quality of the Double Stars” (22nd Series), Monthly Notices of measurements indicating that the usual practice of ana- the Royal Astronomical Society, 90 (3), 317–322, lyzing individual images is more enlightening for sepa- https://doi.org/10.1093/mnras/90.3.317 ration and position angle measurements. Genet, R et al. 2018, Small Telescope Astronomical Conclusion Research Handbook, USA, Sheridan Books. This project has demonstrated to us that it is possi- Harshaw, Richard, 2018, “Gaia DR2 and the Washing- ble for motivated high school students, college under- ton Double Star Catalog: A Tale of Two Data- graduate students, and interested amateur astronomers bases”, JDSO, 14-4, 734-740. His worksheet can to successfully tackle this type of scientific research be found at http://www.jdso.org/volume14/ using available small telescopes. Equipment at the number4/Harshaw_vol14_pg734/ JCDO and the LCO network are capable of making WDSGaiaDR2_Ver3.xlsx . double star measurements with separations down to about 5 arc seconds. Use of the LCO network opens Knapp, Wilfried R. A., 2018, “A New Concept for this experience to the widest possible range of learners/ Counter-Checking of Assumed Binaries”, JDSO, contributors. 14 (3), 487. The methods and equipment used for these meas- Knapp, Wilfried R. A., 2019, “The “True” Movement urements provided consistent results. Differences in of Double Stars in Space”, JDSO, 15 (3), 464. results can be explained by differences in the cameras. It appears this double star system may be gravita- Gaia Collaboration, 2016 “The Gaia Mission”, A & A, tionally bound but it is still not clear. There is very 595, A1. little relative movement over 90 years, yet we estimate Gaia Collaboration, 2018b, “Gaia Data Release 2: Sum- a period of almost 200,000 years. This is the sixth mary of the contents and survey properties”, A & A, measurement of the system. We added another meas- 616, A1. urement for 2015 based on the GAIA DR2 data. These are clustered around the more recent data in which in- LCO scope and camera - SBIG 6303 0.4-meter 0.571 struments and methods have likely improved. Future (bin 1x1) 29\'x19\' 14 s 9; https://lco.global/ measurements and analysis in the distant future could observatory/instruments/sbig-stl-6303/, https:// provide a more definitive answer. This system is wor- lco.global/observatory/telescopes/0-4m/ thy of future study. LCO data pipeline (BANZAI), https://lco.global/ Acknowledgements documentation/data/BANZAIpipeline/ This research made use of the Washington Double AstroImageJ software, https://www.astro.louisville.edu/ Star Catalog maintained at the U.S. Naval Observatory. software/astroimagej/ It also used data and tools at the StelleDoppie.it site created and maintained by Gianluca Sordiglioni. This site has very a capable sorting tool. Historical data was provided by Dr. Brian Mason at the U.S. Naval Obser- vatory. This work also made use of data from the Euro- pean Space Agency (ESA) mission Gaia (https:// www.cosmos.esaint/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 131

An Astrometric Measurement and Analysis of Celestial Motion for WDS 11006-1819

Vladimir Bautista1, Jordan Guillory1, Jae Calanog1, Grady Boyce2, and Pat Boyce2

1. San Diego Miramar College 2. Boyce Astro Research Initiatives and Education Foundation (BRIEF)

Abstract: Our team studied the history of the star system WDS 11006-1819 aiming to construct patterns in determining this system’s double star nature. In doing so, we’ve taken images of the system and performed astrometric measurements. Our calculations yield new measurements for its position angle being 267.8° and separation distance of 63.05". After analyzing the trends in separation angles and distances, irregularity in historical motions of the stars, and the large straight-line distance between the two given by their parallax data, we suggest that WDS 11006-1819 may be an optical binary.

Introduction arcseconds were eliminated. Additionally, the star sys- The goal of this research is to observe and analyze tem was chosen because the most recent observation the position angle (θ) and separation distance (ρ) of was over 9 years ago. It had more than 15 previous ob- WDS 11006-1819 to analyze if this system may be an servations, and its gravitational connection seems to be optical double or a binary star system. Optical double uncertain making it an interesting subject to study. stars are defined as stars that appear close in proximity The United States Naval Observatory (USNO) pro- when viewed from earth, whereas true binary star sys- vided historical measurement data for HJ 1181. The pri- tems orbit around a shared center of mass. The position mary component of HJ 1181 (Referred to as R Crt in angle, theta (θ), is the angle between the stars relative to the SIMBAD catalog) is classified as a red giant one another, measured counterclockwise from the ce- M7/8III star. GAIA data provided an effective tempera- lestial north. The separation, rho (ρ), is the arc distance ture (Teff) of 3295 K. Red giant is a phase in a star’s between the stars. With knowledge of a double star’s life cycle when the hydrogen in its core has ceased to orbital pattern, it is possible to gain accurate measure- be the main method of fusion. As a result, helium is ments of their stellar masses and other aspects of the now the primary contributor to the star’s fusion process. star’s components. Once the stellar masses are known, Its outer shell has expanded tremendously in diameter more information about the star’s size, brightness, and thus its photospheric temperature begins to cool. lifespan, and chemical make-up can be determined. Due to the increase in size, the star’s luminosity also in- WDS 11006-1819 (hereafter referred to as HJ 1181) creased in brightness. Red giants are known to be very is a double star system that can be seen in the southern large stars of high luminosity and low surface tempera- hemisphere during late winter and early spring. The star ture (COSMOS 2019). The second component of HJ was initially observed by Sir John William Herschel, a 1181 (Referred to as HD 95383 in SIMBAD) is a blue great English astronomer and mathematician. This dou- main sequence star with a temperature of 7059 K. Com- ble star system was selected because it met the parame- pared to R Crt, HD 95383 is a much younger star. 90% ters of our research. Since our team’s observation win- of the stars in the universe, including our very own Sun, dow was in spring, we were limited to a Right Ascen- are main sequence stars. They fuse hydrogen atoms to sion (RA) range between 08 - 16 hours. To retain good form helium atoms in their cores. image quality, star systems with a difference magnitude greater than 3 or a separation distance less than 5

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 132

An Astrometric Measurement and Analysis of Celestial Motion for WDS 11006-1819

shows one of our images captured by the LCO. Measurements The calibrated images were exported to As- troImageJ (AIJ) software for plate solving. This process was necessary to properly orient the image in the sky with their correct Right Ascension (RA) and Declina- tion (Dec) identified by Henry-Draper catalog which are linked to SIMBAD. Though our images already had the WCS from the OSS Pipeline, plate solving was done manually to get the needed measurements, such as differential magnitudes (ΔM), which are not available without WCS calibration via Astrometry.net. The separation angle (θ) and separation distance (ρ) were also

measured. Each team member individually measured 8 Figure 2: HJ 1181 using Bessel B filter with 8 seconds images, 16 data points collectively. Calculations were exposure time, A is the primary star (R*Crt) and B is the secondary (HD 95383) (Image shown in AstroImageJ). subsequently performed to determine the statistical error in our measurements of arc length and position an- Methods and Materials gle, as well as the new RA and Dec of the star system HJ 1181. Equipment Measurements were taken from the center of our Data was collected by the Las Cumbres Observato- primary to secondary star, yielding theta (degrees) and ry (LCO), a worldwide network of telescopes. Images rho (arcseconds) measurements, differential magnitude were taken on April 17, 2019 (2019.294 in Besselian (measured by AIJ), as well as RA and Dec. Once all epoch) using a 0.4 m telescope with an SBIG-6303 measurements were completed, the data was exported CCD camera located at the South African Astronomical to an excel spreadsheet for record keeping and analysis. Observatory (SAAO) in Sutherland, South Africa. It The team calculated the statistical error of our new- sits on a hilltop at an altitude of 1,798 m above sea lev- found measurements by finding the mean, standard de- el, near the Karoo village of Sutherland. viation, and the standard deviation of the mean. The Data was collected by the Las Cumbres Observato- same process was performed for the new RA and Dec ry (LCO), a worldwide network of telescopes. Images measurements and the differential magnitudes of the were taken on April 17, 2019 (2019.294 in Besselian two stars. These data can be seen in the Results section. epoch) using a 0.4 m telescope with an SBIG-6303 CCD camera located at the South African Astronomical Resources Observatory (SAAO) in Sutherland, South Africa. It Gaia, Aladin 10 software, the Washington Double sits on a hilltop at an altitude of 1,798 m above sea lev- Star Catalog (WDS), and Stelle Doppie were instru- el, near the Karoo village of Sutherland. mental in providing information that contributes in the Four images were captured using the Bessel B filter construction of our data set. Data for radial velocity for with exposure times of 8 and 9 seconds. Another four HJ 1181 were collected from Gaia via Aladin 10. “Gaia were collected using the Bessel V filter with exposure is an ESA cornerstone mission mapping the point times of 5 and 6 seconds. Both sets of images had an air sources on the sky to a magnitude limit of 20.7. Posi- mass of 1.03. Filters were determined by examining tions are variable due to proper motions which are fun- each star’s effective temperature, provided by SIM- damental elements of the catalogue” (CDS 2019). WDS BAD, and how it peaks at certain wavelength on the provided by the USNO outlined basic information for black body diagram and relating it to the star’s power HJ 1181 such as the epoch, number of observations, output. Trying to avoid oversaturation in our images, first and last measurements for theta (θ) and rho (ρ), we picked these as the most suitable filters and expo- magnitudes, spectral types, proper motions, and the pre- sure times. cise coordinates of the subjects. Supplemental data was Each image has undergone photometric calibration collected from Brian Mason of the USNO regarding our through OSS (Our Solar Siblings) Pipeline, provided by target star system which provided more up-to-date in- Michael Fitzgerald (Fitzgerald 2018). Image calibration formation (Mason 2018). flattens the images, removes bias, noise, hot pixels, cos- Aladin 10 provided visualization of the Gaia data mic rays, etc. World Coordinate System (WCS) has al- for HJ 1181’s proper motions, Figure 2, which show so been processed for each of our images. Figure 1 both A and B stars are moving southwest. The Harshaw

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 133

An Astrometric Measurement and Analysis of Celestial Motion for WDS 11006-1819

Separation Epoch Observer PA (deg) (as) 1828 HJ_1831 270.0 75.00 1866.36 Knt1877 268.5 65.99 1895.7 WFD1908b 267.3 64.95 1907.89 Bu_1913 268.2 65.26 1911.26 Wz_1923 268.0 65.00 1915.12 Gau1926a 267.8 65.21

1915.12 WFC1998 268.1 65.48 Figure 2. Star system WDS 11006-1819 with their proper 1915.12 Poc1916 267.8 65.21 motion provided by GAIA data taken from Aladin 10. 1916.17 Bha1916 267.4 65.36 Method was applied to help determine whether the sys- 1916.17 WFC1998 268.1 64.85 tem is an orbital pair or an optical pair, scoring a rating 1916.17 WFC1998 267.7 65.85 of 46%. The ratings range from 0% ~ 99%, orbital pairs showed small “ratings” nearing towards 0.0, while opti- 1916.26 Gau1926a 267.4 65.42 cal pairs showed high values approaching 100.0 1918.21 Frk1918 269.0 65.04 (Harshaw 2014). 1925.25 Fox1946 268.1 64.96 Results 1933.20 WFC1940a 267.8 64.75 The following results are the average of the group 1969.46 WFC1992 267.9 64.09 members’ independent measurements. Table 1 is the list of HJ 1181’s position angle and separation distance, 1985.44 WFC1994 268.2 63.48 provided by Brian Mason, throughout the years, includ- 1991.61 TYC2000b 267.9 63.61 ing our own measurements highlighted on the bottom. 1997.38 UC_2013b 267.7 65.10 Table 2 shows theta and rho measurements along with the standard deviation and the standard deviation of the 1999.38 UC_2013b 267.6 63.45 mean. Table 3 shows the mean measurements of A and 2000 UC_2013b 267.7 63.49 B stars’ RA and Dec. The statistical error for HJ 1181 2007 Arn2007c 268.3 63.20 system’s newly measured RA and Dec are almost negli- gible. Table 4 shows the parallax data for both compo- 2019.29 Team’s Data 267.8 63.05 nents of HJ 1181 (GAIA Database 2019). Table 5 Table 1. Historical measurements showing the position angle and shows the differential magnitudes between our primary the separation distance dated back to when it was first observed up and secondary star in B and V filter acquired using AIJ to its most recent observation. software.

Discussion PA (deg) Sep (as) There are a total of 22 measurements in the WDS Mean 267.78 63.05 historical record for HJ 1181, plotted on Figures 3 & 4. The initial analysis shows no apparent patterns in the B Std. Dev. ±0.05 ±0.09 star’s motion. The system’s first measurement in 1828 Std. Dev. of the Mean ±0.02 ±0.03 appears to be an outlier as all other measurements of Table 2. Mean measurements and statistical error of the HJ 1181 HD 95383 lie close together between 65 and 63 arcsec- system’s position angle and arclength measured using AIJ. onds away from the A star, Figure 3. Figure 4 is an in- set outlining the dispersion of the measurements. Due

A Star’s RA A Star’s DEC B Star’s RA B Star’s DEC

(hh:mm:ss) (dd:mm:ss) (dd:mm:ss) (dd:mm:ss)

Mean 11:00:32.4 -18:19:30.0 11:00:28.8 -18:19:33.6

Table 3. Mean measurements of RA and Dec of A and B Stars.

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 134

An Astrometric Measurement and Analysis of Celestial Motion for WDS 11006-1819

A Star’s RA A Star’s DEC B Star’s RA B Star’s DEC

(hh:mm:ss) (dd:mm:ss) (dd:mm:ss) (dd:mm:ss)

Mean 11:00:32.4 -18:19:30.0 11:00:28.8 -18:19:33.6

Table 3. Mean measurements of RA and Dec of A and B Stars.

Parsecs Light Years Results Min Distance Mid Point Max Distance Min Distance Mid Point Max Distance Star A 225.25 236.29 248.48 734.32 770.32 810.04 Star B 344.72 351.10 357.72 1123.79 1144.58 1166.16

Table 4. Parallax data and Straight-Line distance provided by SIMBAD and calculated using Harshaw's Parallax Calculator

Standard Deviation of the Filter Mean Standard Deviation Mean B 0.217 ±0.008 ±0.004

V 1.757 ±0.009 ±0.005

Table 5. Differential Magnitudes between A and B stars in Bessel B and V filters.

to the scatter of the measurements, a discernable pattern orbital pair. This leaves us to look for other ways in de- cannot be used to suggest the gravitational nature of HJ termining the nature of HJ 1181. 1181. Further analysis of the parallax data from SIMBAD, In the paper “Another Statistical Tool for Evaluat- seen in Table 4, of each star was performed to find the ing Binary Stars,” Richard Harshaw proposed another minimum radial distance between the two stars of 374.6 way of determining whether a double star is a binary by light years. We know that the straight-line distance be- examining the proper motion of the given pair tween to two stars cannot be smaller than the radial dis- (Harshaw 2014). Using this method, our double star tance because of the laws of trigonometry. Thus, the had a rating of 46% which provides no clarity in deter- straight-line distance between the two stars must be mining whether HJ 1181 system is an optical pair or an greater than 374.6 light years. In a paper published by

Figure 3: Plot of B star’s movement relative to A star on Figure 4: Plot of B star movement relative to the A star on the the origin. The red triangle is the new data point. The red origin excluding the first observation that was taken in 1828. square is the first data point taken in 1828. The red triangle is the new data point.

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 135

An Astrometric Measurement and Analysis of Celestial Motion for WDS 11006-1819

the University of Hawaii Institute of Astronomy, it is Mason, Brian, 2018, Washington Double Star Catalog, shown that the greatest straight-line distance between Astronomy Department, United States Naval Ob- binary stars is one light year (Good, et al. 2018) which servatory, http://ad.usno.navy.mil/proj/WDS/. is two orders of magnitude smaller than the smallest Sordiglioni, Gianluca, 2018, Stella Doppie Double Star possible distance between the two components of HJ Catalog, https://www.stelledoppie.it/index2.php? 1181. iddoppia=49218. Conclusion Wenger, et al., 2000, “The SIMBAD astronomical data- Though the two stars share a similar common prop- base”, A&AS, 143, 9. Dictionary of Nomenclature er motion, the movements of the B star relative to the A of Celestial Objects (Last Update: 03-May-2019).” star cannot be used to suggest an orbit, but instead CDS: GAIA. http://cds.u-strasbg.fr/cgi-bin/Dic- shows possible characteristics of a Common Proper Simbad?Gaia%20DR2. Motion (CPM) pair. However, the nature of HJ 1181 can be definitively determined. Statistically, different Las Cumbres Observatory Network https://lco.global/ parallax for star components suggest they are non- observatory/sites/. physical pair. The parallax data from A and B stars in- Red giant stars | COSMOS. (n.d.). Retrieved May 15, dicate that the two are most probably not gravitationally 2019 from http://astronomy.swin.edu.au/cosmos/R/ bound because of the great distance between them. Red+giant+stars. Acknowledgements We would like to thank the Boyce Research Initia- tives and Educational Foundation (BRIEF) as well as Jae Calanog, Theophilus Human, and Marielle Cooper of San Diego Miramar College for their guidance and mentorship that was necessary in finishing this paper. In addition, our team would like to thank Channel Arre- ola for helping us during the preliminary stage of this research paper. Special thanks to Las Cumbres Obser- vatory for supplying our images necessary for our measurements, Michael Fitzgerald for image calibration, and to Brian Mason of the USNO for providing access to our system’s historical data via the Washing- ton Double Star catalog. References Boyce, G. and Boyce, P. Boyce, Research Initia- tives and Education Foundation (BRIEF), http:// www.boyce-astro.org/home.html Good, Louis and Reipurth, Bo, 2018, “Wide Binary Stars: Long-Distance Stellar Relationships”, Insti- tute for Astronomy, University of Hawaii, http:// www.ifa.hawaii.edu/info/press-releases/ WideBinaryStars/ Fitzgerald, M.T., 2018, “The Our Solar Siblings Pipe- line: Tackling the data issues of the scaling problem for robotic telescope based astronomy education projects.”, Robotic Telescopes, Student Research and Education Proceedings. Harshaw, R., 2014, “Another Statistical Tool for Evalu- ating Binary Stars”, JDSO, 10, 32.

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 136

Astrometric Measurement of WDS 13433-2458 AB

Roswell Roberts1, Derek Chow1, Kevin Lu1, Marie Yokers2, Pat Boyce3, and Grady Boyce3

1. Westview High School, San Diego, California, USA 2. San Diego Mesa College, San Diego, California, USA 3. Boyce Research Initiatives and Education Foundation, San Diego, California, USA

Abstract: By utilizing Las Cumbres Observatory (LCO) telescopes equipped with CCD imaging, measurements of theta and rho of the proposed binary system WDS 13433-2458 AB (HJ 2671) were determined. When compared to the 18 previous measurements of the system however, the data shows no signs of orbital motion and suggests that WDS 13433-2458 AB is not a physical double.

Introduction By determining the true nature of binary and multiple star systems—whether or not they are gravitationally bound—can assist astronomers in determining the masses of each star and other stellar characteristics such as radius, density, and a mass-luminosity relationship (MLR), can be estimated. As part of the Boyce Re- search Initiatives and Education Foundation (BRIEF), this research project aims to assist in the verification of whether a system is a gravitationally bound double or an optical double. WDS 13433-2458 AB (HJ 2671AB) was selected after meeting the following criteria: right ascension (RA) of 12 to 16 hours for reduced air mass during imaging, delta magnitude of 3 or less, and separation of 5 to 15 arcseconds for image clarity. Materials and Methods Historical data for HJ 2671 AB was furnished by the United States Naval Observatory, from which we derived a historical chart of theta and rho over time, Figure 1. The first measurement of HJ 2671 was in 1831 and was measured a total of 18 times with the most re- Figure 1: Historical Graph cent observation being in 2016. Several sources, the Washington Double Star Catalog (WDS), GAIA, and Aladin 10 were consulted for stellar data such as radial velocity, proper motion vectors, and parallax data. Key ing Portal with exposure times calculated using the LCO data points from GAIA are shown in Table 1. Exposure Time Calculator. SBIG CCD cameras with The Las Cumbres Observatory (LCO) 0.4m tele- 2048 X 3072 pixels had a resolution of 0.57" per pixel scopes were used to observe HJ 2671AB. Requests for and a field of view of 19′ X 29′. An SDSS-g filter was these images were processed through the LCO Observ- used to photograph HJ 2671 on Julian Date

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 137

Astrometric Measurement of WDS 13433-2458 AB

Primary Star Secondary Star

HJ 2671 A HJ 2671 B Proper Motion -33.407 -38.895 RA Proper Motion 0.109 0.089 RA Error Proper Motion -14.294 0.8 Dec Proper Motion 0.108 0.081 Dec Error Parallax 7.9587 1.8924

Parallax Error 0.0588 0.047

Radial Velocity -13.12 -79.31 Radial Velocity 0.69 0.35 Error Table 1: Table of GAIA data

2458580.655185208 for a total of 12 images at 3 seconds exposure time each. With this telescope setting we determined that of 2458580.655185208 HJ 2671 AB had a theta value of 66.099 degrees and a rho value of 27.507 arcseconds. Each image was processed through the Our Solar Sisters (OSS) Pipeline to remove image imperfections and insert World Coordinate System (WCS) coordinates into the image files (Fitzgerald 2018). As- troImageJ (AIJ) was used to provide measurements of theta and rho (igure 2) in order to compare them to the measurements found in the historical data. Figure 2: Images of HJ 2671 AB being measured in AstroimageJ Results Epoch Std Dev Table 1 gives the data obtained from the GAIA da- Mean Std Dev 2019.264 of Mean tabase. Table 2 shows the Mean, Standard Deviation, and Standard Error of the Mean for the position angle θ(deg) 66.099 0.065 0.021 (θ) and separation (ρ) measured for HJ 2671AB. ρ(as) 27.505 0.028 0.009

Discussion Table 2. The mean, standard deviation, and standard dev of the A graph of the historical data of the star (figure 1, mean of the data collected above) gives a clear pattern in the movement of the B star. The trend indicates that the B star is moving in a Northwesterly direction with a proper motion value of that they are moving away from Earth together. <-38.895, 0.800>. However, the A star in the system is Analysis of this data suggests that the stars are not not moving with the B star and instead is moving in a moving together and instead are pursuing different Southwesterly direction with a proper motion value of paths through space. This is further supported by paral- <-33.407, -14.294>, which is illustrated in Figure 3 lax data acquired from the GAIA satellite. The A star where the proper motion vectors of the A and B star has a parallax of 7.9587 and an error of 0.0588, which have been superimposed onto the image. Additionally, puts the A star at a distance of 406.61 to 412.66 light data from the GAIA satellite reveals that the radial ve- years away from Earth. The B star’s parallax is 1.8924 locities of the A and B star respectively are -13.12 and - with a parallax error of 0.0471, placing the B star at a 79.31. Since both of these values are negative, the two distance of 1681.19 to 1767.03 light years away, mak- stars are moving away from Earth but because there is a ing the two stars separated by at least 1268.53 light 66.19 difference in radial velocities, we do not believe years. The distance by which these two stars are sepa-

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 138

Astrometric Measurement of WDS 13433-2458 AB

and use of the LCO Worldwide telescope systems. We also thank the Boyce Research Initiatives and Educa- tion Foundation (BRIEF) for their generous support throughout the study that allowed us to access the remote telescope system and software necessary. Addi- tionally, we thank Michael Fitzgerald at the OSS Pipe- line for processing images and removing imperfections made by the camera. This work has made use of data from the European Space Agency (ESA) mission{\it Gaia} (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC,https://www.cosmos.esa.int/web/gaia/dpac/ consortium. Funding for the DPAC has been provided by national institutions, in particular the institutions Figure 3. An image of HJ 2671 AB with proper motion vectors participating in the Gaia Multilateral Agreement. References rated is considerable and considering the inverse square Collins, K. A., Kielkopf, J. F., Stassun, K. G., and relationship between the force of gravity and distance, Hessman, F. V., 2018, “AstroImageJ: image pro- we do not believe that HJ 2671 A is gravitationally cessing and photometric extraction for ultra-precise bound to HJ 2671 B over a distance of 1268.53 light astronomical light curves”, The Astronomical Jour- years. nal, 153(2), 77. Conclusion Fitzgerald, M.T., 2018, “The Our Solar Siblings Pipe- The large distance between the A and B stars, the line: Tackling the data issues of the scaling problem lack of a trend indicative of an orbit on the historical for robotic telescope-based astronomy education graph with our measurements added to it, and the dif- projects.”, Robotic Telescopes, Student Research ference in proper motion vectors indicate that the star and Education Proceedings. system is not a physical double. However, inconsisten- Mason, B. and Hartkopf, W., 2015, The Washington cies with historical data and measurement differences Double Star Catalog, Astrometry Department, U.S. of separation and position angle warrants further obser- Naval Observatory. vation of the system.

Acknowledgments We thank Brian Mason and the United States Naval Observatory for providing historical measurement data

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 139

Discovery of 3 New Optical Double Stars in Constellation Cygnus

Joerg S. Schlimmer

Seeheim-Jugenheim, Germany [email protected]

Abstract: During observations of ES 361 (HD 333501) in constellation Cygnus also HD 333510 and two further stars could be found as optical double stars

During my observation program of Espin’s double stars, I did some investigation on ES 361 because it wasn’t marked as double star in my planetary software [Redshift] which was used for telescope control. For identification I first made some photos with a Canon 1100D DSLR Camera of the field of ES 361 with different exposure times. In this way, 3 new interesting double stars could be found, which were not listed in WDS catalog or marked as double stars in my planetary software. On the next observation night, these stars were targeted. Some videos with a QHY 5LII-C CMOS were recorded for later data analysis with REDUC software [Losse]. All observations were done with a 12- inch Newtonian telescope. Focal length was 1500 mm. 1. HD 333510 Similar to ES 361, HD 333510 could also be found

as a high contrast double star. The distance between ES Figure 1: HD 333510, 74 frames taken with QHY 361 and HD 333510 is about 20.5'. The coordinates of 5LII-C CMOS were stacked HD 333510 are 20h 06' 40.36" in RA and +30° 30' 28.57" in declination. Visual brightness of HD 333510 3.16" and a position angle of 87.8°. Proper motion isn’t is 9.08 magnitudes. Estimated contrast between primary known. and secondary is about 3.4 magnitudes, so a brightness of about 12.5 magnitudes can be assumed for the sec- 3. USNO B1.0 1206-0471593 ondary. Separation is 6.64", position angle is 43.9°. Be- Only 154’’ from USNO B1.0 1206-0471593 a fur- cause proper motion of HD 333510 is very small (1.191 ther faint double star USNO B1.0 1206-0471593 can be -1.924 mas/y), it may be take a while until the true rela- found, see also figure 2. Coordinates are 20h 07m tionship between the two is known. 41.454s in RA and +30°44’31.81’’ in declination. Dis- tance to ES 361 is about 14’. The brightness is only 2. USNO B1.0 1206-0471491 11.5 magnitudes estimated contrast is about 0.8 magni- USNO B1.0 1206-0471491 can be found next to tudes. It could be found a separation of 3.93" and a po- TYC 2671-02093-1, see Figure 2. Coordinates are 20h sition angle of 42.6°. Proper motion isn’t also known. 07' 37.147" in RA and +30°42'08.49" in declination. Table 1 shows the summary of the new optical dou- Brightness is only 11.5 magnitudes, estimated contrast ble stars. is 0.6 magnitudes. It could be found a separation of

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 140

Discovery of 3 New Optical Double Stars in Constellation Cygnus

Name RA +Dec Mags PA Sep Date N HD 333510 20 06 40.36 +30 30 28.57 9.08 12.5 43.9 6.64 2019.714 1 USNO B1.0 1206-0471491 20 07 37.15 +30 42 08.49 11.5 12.1 87.8 3.16 2019.714 1 USNO B1.0 1206-0471593 20 07 41.45 +30 44 31.81 11.5 12.3 42.6 3.93 2019.714 1 Table 1. Summary of New Optical Double Stars

Acknowledgments This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France This research has made use of the Washington Double Star Catalog maintained at the U.S. Naval Ob- servatory. References Losse, Florent, http://www.astrosurf.com/hfosaf/uk/ tdownload.htm#reduc. Redshift 7, www.redshift-live.com. Schlimmer, S. Joerg, 2018, “Double Star Measurements Using a Webcam and CCD Camera, Annual Report of 2016”, JDSO, 14 (1), 22-29.

Figure 2. USNO B1.0 1206-0471593 and USNO B1.0 1206- 0471491, 200 frames taken with QHY 5LII-C CMOS were stacked

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 141

Double Star Measures Using the Video Drift Method - XIII

Richard L. Nugent International Occultation Timing Association [email protected]

Ernest W. Iverson International Occultation Timing Association [email protected]

Abstract: Position angles and separations for 206 multiple star systems are presented using the video drift method.

Introduction ation squared. In Table 1 we report the Standard Error This is Paper XIII in our continuing series on dou- of the Mean (SEM) which is the weighted standard de- ble star measurements using the video drift method first viation divided by the square root of the number of proposed by Nugent and Iverson 2011. We continue our nights measurements were made. In the case of double practice of preferentially measuring multiple star sys- star systems measured on only one night, the SEM is tems listed in the Washington Double Star Catalog equivalent to the nightly standard deviation (Nugent (WDS) that have not been measured for a minimum of and Iverson 2018). This practice gives a higher error 10-15 years and have less than 10 measurements. Meas- value than if a multi night SEM were calculated. We urements are limited to systems with a separation great- do not report the weighted standard deviation because it er than 3.2". This separation represents the current min- produces an artificially lowered error measure as the imum resolution of the video drift method with our number of nights increases. equipment. To reach fainter systems, image enhancement techniques were employed. Co-author Iverson used a varia- Methodology tion of the drift method employing an integrating video The techniques used in this paper are the same as in camera (Iverson and Nugent 2015) while co-author our previous paper (Nugent and Iverson 2018). All Nugent used a Collins I3 image intensifier with a non- measurements were made with a pair of Meade 14-inch integrating camera. The faintest system measured in LX-200 telescopes (focal length 3556 mm at f/10, scale Table 1 had primary/secondary magnitudes of +10.36, factor 0.6"/pixel). Astronomical video data collection +14.29. Sixteen systems had WDS magnitudes in the systems require a onetime aspect ratio calibration. The range +13.0 to +14.29. reader is referred to our previous discussion of the Occasionally we would come across systems in problem and calibration procedure (Nugent and Iverson which there was a large magnitude difference between 2014). the components. At a nominal gain setting for our video A simple average was calculated to determine the cameras the fainter (secondary) component was usually mean PA and SEP for each night. A mean standard not visible, therefore position measurements could not deviation was also calculated for each night’s observa- be made. If it was visible, the primary (brighter) com- tion. Since we frequently made measurements on sev- ponent was overly saturated on the video chip sensor eral nights the means were combined using a weighted and thus too large to be measured by the restricted size average. The weight assigned to each night’s measure- of the measurement aperture in the Limovie program. ment is simply the inverse of that night’s standard devi- The solution is to make two separate drift runs at differ-

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 142

Double Star Measures Using the Video Drift Method - XIII

ent gain settings using the same video frames so that References each component was visible and thus could be meas- Iverson, E. and Nugent, R., 2015, Journal of Double ured; then combine the measurements from both runs to Star Observations, 11, (2), 91-97. derive a position angle and separation. Other systems had very close separations causing Nugent, R. and Iverson, E., 2011, Journal of Double the components to merge at our nominal scale factor of Star Observations, 7, (3), 185-194. 0.6"/pixel. This issue was resolved by using a magnifi- Nugent, R. and Iverson, E., 2014, Journal of Double cation script on the video. The video was enlarged sig- Star Observations, 10, (3), 214-222. nificantly into three sections (typically scale 0.2"/pixel or less) allowing the components to be resolved and Nugent, R. and Iverson, E., 2018, Journal of Double measured. Both of the above techniques have been dis- Star Observations, 14, (3), 566-576. cussed previously (Nugent and Iverson 2018).

Acknowledgements This research makes use of the Washington Double Star Catalog maintained at the US Naval Observatory.

Discover PA Sep. Avg. Position PA Sep. Mag 1 Mag 2 Drifts Nights Code SEM SEM Date 00020+2347 TVB 2 291.8 0.02 28.10 0.04 2019.80 8.98 9.63 15 3 00040+4942 TOB 9 25.6 0.04 43.90 0.04 2019.87 9.08 9.84 15 3 00078+5723 HJ 3241 8.6 0.03 14.90 0.02 2019.87 9.16 9.83 15 3 00104+4952 ES 2576 294.2 0.03 77.04 0.04 2019.87 8.62 8.72 15 3 00108+5846 ARY 8AB 100.7 0.04 39.24 0.04 2019.87 8.13 8.63 15 3 00108+5846 ARY 8AC 42.8 0.04 104.65 0.05 2019.87 8.13 8.29 15 3 00125+4625 D 1 74.0 0.04 13.92 0.01 2019.80 9.66 10.35 20 4 00227+2434 HJL1003 252.1 0.05 74.29 0.05 2019.80 8.80 9.69 20 4 00545+5619 CTT 2 42.0 0.03 59.63 0.03 2019.81 7.18 9.83 15 3 01147+4255 ARG 49AB 105.9 0.02 35.72 0.03 2019.80 8.79 10.03 15 3 01147+4255 ARG 49AC 103.5 0.05 23.81 0.03 2019.80 8.79 10.29 15 3 01147+4255 ARG 49BC 290.7 0.03 11.96 0.01 2019.80 10.03 10.29 15 3 01175+2105 STF 107 68.7 0.07 21.06 0.02 2019.81 8.82 10.69 15 3 02042+5257 HJ 2104 170.3 0.04 30.41 0.04 2019.81 9.35 9.61 15 3 02282+5423 HJ 5535CD 145.1 0.02 19.67 0.01 2019.81 10.54 11.16 15 3 02282+5423 STF 267AB 28.7 0.07 94.17 0.10 2019.81 8.97 8.95 15 3 02282+5423 STF 267BC 25.5 0.02 69.04 0.01 2019.81 8.95 10.54 15 3 02580+4650 VLM 7 175.5 0.04 11.73 0.02 2019.81 9.6 9.6 15 3 03009+5940 STTA 31 230.5 0.05 73.90 0.06 2019.81 7.33 8.03 15 3 08054+0812 STF1181 141.2 0.21 5.17 0.02 2019.18 8.28 9.26 25 5 08137+0407 ARG 68 325.8 0.07 51.88 0.13 2019.18 9.54 10.01 25 5 08242+3737 ES 1732 83.2 0.24 18.74 0.04 2019.18 9.58 10.3 25 5 08400+2009 ARN 105 153.2 0.09 91.16 0.31 2019.18 8.89 9.69 25 5 08435+4852 STF1258 330.8 0.08 10.14 0.01 2019.18 7.72 7.87 25 5

Table 1. Results of 206 double stars using the video drift method. Table continues on the next page.

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 143

Double Star Measures Using the Video Drift Method - XIII

Discover PA Sep. Avg. Position PA Sep. Mag 1 Mag 2 Drifts Nights Code SEM SEM Date 09032+0140 XMI 87 306.1 0.11 26.87 0.18 2019.18 9.36 10.63 25 5 09227+5036 STF1341 88.9 0.21 20.46 0.10 2019.18 9.09 9.17 25 5 09251+2915 CTT 22 42.8 0.16 89.03 0.16 2019.18 9.4 9.9 25 5 09307+4502 FLA 1 238.8 0.09 34.00 0.06 2019.18 9.61 10.58 25 5 09309+4441 STF1358 176.4 0.06 24.14 0.07 2019.18 7.93 9.25 25 5 09357+5318 STF1366 320.6 0.18 7.77 0.04 2019.18 8.44 10.09 20 4 09361+5318 STF1368 219.8 0.12 21.85 0.02 2019.18 8.79 10.45 25 5 09505+4505 CBL 38 11.6 0.08 52.21 0.05 2019.18 7.46 11.71 25 5 11076-1732 ARA 225AB 171.3 2.70 8.00 0.46 2019.33 11.9 11.9 5 1 11076-1732 WNO 28AC 132.4 2.24 31.84 1.24 2019.33 12.24 13.66 5 2 11084+0313 H 5 68AB 226.4 0.11 143.71 0.31 2019.33 7.74 9.24 3 1 11084+0313 SLE 686AC 222.0 0.13 185.73 0.39 2019.33 7.74 11.88 3 1 11084+0313 H 5 68BC 206.6 0.57 43.20 0.37 2019.33 9.24 11.88 3 1 11285+0750 WLF 1AB 335.7 0.15 114.69 0.33 2019.33 10.34 10.51 3 1 11285+0750 WLF 1AC 300.9 0.11 236.60 0.50 2019.33 10.34 12.88 3 1 11285+0750 WLF 1BC 276.1 0.15 156.93 0.43 2019.33 10.51 12.88 3 1 11349-1325 BRT2729 227.8 1.26 3.92 0.09 2019.33 10.3 11.2 9 1 11390-0950 J 2083 112.6 2.03 4.78 0.19 2019.33 11.99 13.0 5 1 11404-0606 ROE 73AC 57.2 0.08 84.85 0.11 2019.33 11.56 11.08 9 1 11484-1019 H 6 115BC 352.2 0.18 100.74 0.28 2019.33 9.17 12.55 3 1 11518-0335 J 1581AB 223.7 2.03 6.53 0.24 2019.33 10.60 13.8 3 1 11561-0409 BRT 436 192.5 1.03 3.21 0.09 2019.33 11.89 12.35 9 1 11584+2352 POU3119 175.0 2.29 11.63 0.53 2019.34 13.40 13.82 3 1 12019-4100 WG 148 291.3 3.39 7.41 0.38 2019.34 11.52 12.4 3 1 12051-2335 DON1096 168.0 0.88 5.26 0.08 2019.33 10.37 12.7 9 1 12053-3511 LDS 854 114.7 1.02 28.23 0.48 2019.33 10.69 13.43 3 1 12085-0259 BAL 219 16.9 2.15 7.66 0.27 2019.34 10.65 12.9 3 1 12110-2934 BRT2991 132.0 0.96 5.38 0.09 2019.34 10.56 12.9 9 1 12141-3644 SEE 147AB,C 306.4 0.69 27.83 0.31 2019.34 8.53 11.72 3 1 12219-0237 HLD 12AC 314.5 0.66 50.23 0.65 2019.34 10.36 14.29 3 1 12219-0237 HLD 12AD 306.8 0.15 117.76 0.33 2019.34 10.36 12.11 3 1 12242-3224 HJ 4519AB 89.2 1.20 8.91 0.26 2019.34 9.8 11.4 3 1 12247+0225 AG 177AB 220.5 1.51 7.30 0.20 2019.34 9.35 10.64 3 1 12247+0225 AG 177AC 57.4 0.20 96.27 0.33 2019.34 9.35 12.94 3 1 12256-0737 HDS1747 330.5 1.31 7.99 0.19 2019.33 9.36 11.97 3 1 12265-0153 HLD 13AC 71.9 0.14 130.75 0.34 2019.34 9.72 12.38 3 1 12267-2850 FOX 174 311.4 1.47 13.94 0.36 2019.33 9.6 12.1 3 1 12290+3735 KZA 36AB 114.7 0.31 57.13 0.26 2019.34 9.12 12.86 3 1 12290+3735 KZA 36AC 322.8 0.22 83.67 0.27 2019.34 9.17 13.12 3 1 12333-2410 ARA2180 276.0 2.17 6.32 0.29 2019.33 11.4 11.8 3 1

Table 1 (continued). Results of 206 double stars using the video drift method. Table continues on the next page.

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 144

Double Star Measures Using the Video Drift Method - XIII

Discover PA Sep. Avg. Position PA Sep. Mag 1 Mag 2 Drifts Nights Code SEM SEM Date 12383-1131 STF1664AB 223.2 0.32 38.71 0.23 2019.33 7.82 9.17 3 1 12383-1131 STF1664AC 306.4 0.21 60.70 0.25 2019.33 7.82 11.52 3 1 12383-1131 STF1664AD 290.9 0.20 83.77 0.34 2019.33 7.82 12.43 3 1 12383-1131 STF1664AE 109.8 0.12 121.38 0.27 2019.33 7.82 8.58 3 1 12383-1131 STF1664BC 340.9 0.22 68.09 0.28 2019.33 9.17 11.52 3 1 12383-1131 STF1664BD 318.2 0.25 77.91 0.34 2019.33 9.17 12.43 3 1 12383-1131 STF1664CD 258.1 0.58 30.00 0.35 2019.33 11.52 12.43 3 1 12383-1131 STF1664EF 111.5 0.15 92.73 0.27 2019.33 8.58 8.91 3 1 12392-0800 ENG 47BC 61.2 0.12 105.63 0.22 2019.33 8.80 10.56 3 1 12406+4017 HJ 2617AB 1.9 1.24 5.37 0.12 2019.34 8.41 9.61 3 1 12406+4017 HJ 2617AC 175.6 0.08 168.72 0.18 2019.34 8.41 11.02 3 1 12406+4017 BKO 114AD 343.2 0.47 43.05 0.20 2019.34 8.41 13.78 3 1 12432-2722 B 2300 314.5 2.10 10.61 0.34 2019.33 8.97 13.0 3 1 12464-4605 I 9024AC 215.4 0.97 24.51 0.29 2019.34 10.04 13.0 3 1 12481-3542 SEE 161AB 108.2 0.54 34.19 0.29 2019.33 9.21 11.67 3 1 12481-3542 SEE 161BC 95.9 1.12 5.55 0.12 2019.33 12.4 13.4 9 1 12490-1217 J 2086 299.7 1.77 5.81 0.21 2019.33 10.4 12.0 9 1 12525-4603 CPO 354 282.0 2.37 8.60 0.29 2019.34 11.2 12.2 3 1 13011-3337 HJ 4563 236.7 0.31 5.73 0.04 2019.33 7.02 8.23 9 1 13038-3415 SEE 169 236.4 0.74 10.34 0.15 2019.33 7.22 11.5 3 1 13058-0503 A 10AC 55.6 0.21 72.96 0.24 2019.33 11.47 10.50 3 1 13108-4404 CPO 363 87.9 0.86 5.07 0.10 2019.34 10.97 12.5 9 1 13127-2258 ARA1797 50.3 1.68 9.29 0.25 2019.33 10.41 11.6 3 1 13153+1612 SLE 917 298.5 0.53 28.30 0.22 2019.33 8.71 12.72 3 1 13208-0431 BRT 446 296.9 0.65 14.47 0.19 2019.33 11.25 11.7 9 1 13216+1717 GRV 866AB,C 295.5 0.24 64.19 0.27 2019.33 10.32 10.99 3 1 13236+3608 KZA 61AB 108.8 0.24 88.07 0.34 2019.34 11.65 11.74 2 1 13236+3608 KZA 61AC 292.5 0.20 158.90 0.54 2019.34 11.65 13.31 2 1 13239-2346 ARA2185 234.4 2.22 9.04 0.33 2019.33 11.3 12.5 3 1 13253+1033 HJ 227AB 314.8 0.37 39.71 0.25 2019.34 9.02 10.59 3 1 13253+1033 STU 8AC 212.5 0.25 77.70 0.35 2019.34 9.02 12.19 3 1 13253+4028 HJ 1231AB 14.4 0.63 24.04 0.22 2019.34 8.67 12.5 3 1 13253+4028 HJ 1231AC 52.9 0.14 90.35 0.18 2019.34 8.67 8.85 3 1 13253+4028 BKO 49AD 202.3 0.41 39.22 0.22 2019.34 8.85 12.89 3 1 13277-4312 I 400AC 263.3 1.01 17.22 0.23 2019.34 9.25 13.83 3 1 13277-4312 DAM 23AD 311.0 0.42 43.81 0.27 2019.34 9.25 9.58 3 1 13291+2211 STF1748AB 183.9 1.77 5.74 0.13 2019.34 8.26 10.85 3 1 13291+2211 STF1748AC 183.9 0.12 138.87 0.24 2019.34 8.26 11.00 3 1 13325+1428 FOX 178 26.6 2.36 12.06 0.47 2019.34 9.67 13.0 3 1 13328+2242 POU3143 154.2 1.61 13.12 0.33 2019.34 10.16 12.6 3 1

Table 1 (continued). Results of 206 double stars using the video drift method. Table continues on the next page.

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 145

Double Star Measures Using the Video Drift Method - XIII

Discover PA Sep. Avg. Position PA Sep. Mag 1 Mag 2 Drifts Nights Code SEM SEM Date 13330-0225 HLD 15AB 296.6 0.57 16.57 0.20 2019.33 7.36 12.1 3 1 13330-0225 HLD 15AC 249.2 0.14 144.53 0.34 2019.33 7.36 12.32 3 1 13367+2847 GRV 870AB,C 118.0 0.69 22.39 0.24 2019.34 9.72 11.67 3 1 13372-2957 HJ 4599 206.6 1.97 7.78 0.23 2019.33 10.75 11.66 3 1 13376-1048 STF1762AB 275.1 0.81 4.40 0.07 2019.33 9.39 9.88 9 1 13376-1048 UC 2570AC 256.5 0.06 85.59 0.07 2019.33 9.39 12.46 9 1 14008-1108 GWP2174AB 183.6 0.43 76.23 0.52 2019.33 12.1 13.9 3 1 14060+0315 A 2168AC 110.9 0.99 23.63 0.48 2019.33 9.55 13.7 3 1 14303-2020 B 2769 249.2 1.11 13.79 0.24 2019.34 9.15 12.2 3 1 14310-4351 HDS2049AB 226.0 1.91 8.33 0.23 2019.34 8.82 10.11 3 1 14310-4351 FAB 13AC 230.7 0.98 24.57 0.33 2019.34 8.82 10.40 3 1 14326-2327 ARA2188 177.2 1.09 9.17 0.31 2019.34 10.6 12.7 3 1 14398-3833 I 1576AC 230.2 1.01 18.92 0.27 2019.34 9.11 12.54 3 1 15569+3604 HJ 258 253.2 0.06 16.63 0.02 2019.52 10.40 11.20 15 3 16160+1126 ENG 56AB 252.2 0.23 61.63 0.28 2019.56 7.37 10.60 3 1 16160+1126 BUP 166AC 342.4 0.31 86.81 0.43 2019.56 7.37 12.34 3 1 16160+1126 BUP 166BC 17.2 0.22 106.61 0.22 2019.56 10.60 12.34 3 1 16197+1054 KU 52AB 49.7 1.68 9.45 0.26 2019.56 10.14 11.5 3 1 16197+1054 KU 52AC 276.3 0.17 83.51 0.25 2019.56 10.14 11.26 3 1 16212-2958 B 1319AB 130.4 1.85 7.64 0.26 2019.56 9.99 11.3 3 1 16304+0140 SKF1592 220.3 0.04 63.15 0.05 2019.52 8.87 9.30 15 3 16418+1309 LBU 15AB 327.1 0.15 81.03 0.20 2019.56 8.02 9.86 3 1 16418+1309 LBU 15AC 223.3 0.15 39.42 0.10 2019.56 8.02 12.82 3 1 16450+0605 STT 585BC 323.0 0.09 152.42 0.25 2019.56 10.40 10.77 3 1 16450+0605 STT 585CP 107.9 0.22 105.15 0.38 2019.56 10.77 12.8 3 1 16458+0835 SHJ 239BC 131.5 0.26 96.90 0.24 2019.56 9.29 12.38 3 1 17003+1958 SLE 4 283.4 0.05 11.42 0.01 2019.56 10.82 10.90 20 4 17118+2906 SLE 11 285.5 0.08 9.21 0.01 2019.56 11.36 12.3 15 3 17120+2859 GRF 3 185.9 0.03 96.54 0.09 2019.52 9.70 10.09 25 5 17155-2346 ARA2200 194.6 2.93 6.58 0.39 2019.56 11.6 12.0 3 1 17174+1939 COU 496AC 250.1 3.16 7.35 0.42 2019.56 11.3 12.8 3 1 17189-2029 ARA1124 72.7 2.55 6.55 0.33 2019.56 11.4 11.9 3 1 17189-2400 H 6 54AC 141.5 0.23 79.01 0.32 2019.56 9.73 9.74 3 1 17244-0538 J 1615 187.6 2.13 6.93 0.23 2019.56 10.95 12.9 3 1 17284+2950 ARY 13 88.8 0.04 102.92 0.06 2019.56 8.57 8.91 20 4 17287-2235 B 2837 224.7 1.58 12.99 0.33 2019.56 9.61 12.10 3 1 17529+0744 SKF2779 62.0 0.05 67.72 0.07 2019.56 8.4 10.1 15 3 18041+0628 STF2265 281.9 0.03 23.45 0.02 2019.56 9.91 10.59 15 3 18264+4649 STT 352 220.3 0.03 24.52 0.02 2019.56 7.91 9.38 30 6 18386+4901 CBL 171 260.1 0.04 47.50 0.04 2019.56 9.49 10.74 30 6

Table 1 (continued). Results of 206 double stars using the video drift method. Table continues on the next page.

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 146

Double Star Measures Using the Video Drift Method - XIII

Discover PA Sep. Avg. Position PA Sep. Mag 1 Mag 2 Drifts Nights Code SEM SEM Date 18404+0942 S 704 263.8 0.03 58.08 0.05 2019.64 8.49 9.07 15 3 18479+1110 STTA174 158.5 0.07 104.56 0.09 2019.64 7.51 8.32 15 3 18577+0942 HJ 5505 122.1 0.07 14.43 0.02 2019.52 9.41 9.46 25 5 19019+2718 ES 479 142.2 0.08 8.41 0.01 2019.56 9.3 10.5 20 4 19021+0230 BAL1973 189.7 0.04 10.68 0.04 2019.56 9.45 11.09 10 2 19031+0350 HJL1100 21.1 0.02 88.56 0.05 2019.64 8.35 9.22 15 3 19037+1658 STF2442 209.6 0.07 9.94 0.02 2019.64 8.48 9.77 15 3 19100+4941 JKA 30 76.7 0.03 61.77 0.05 2019.56 7.99 9.90 20 4 19190+3934 DEA 466 258.2 0.03 40.36 0.07 2019.64 8.8 10.7 15 3 19196+2321 POU3765 230.2 0.05 16.08 0.02 2019.56 9.56 10.98 20 4 19248+1215 SKF 921 237.3 0.04 54.03 0.08 2019.56 9.73 10.67 20 4 19250+1157 COM 7AD 190.6 0.01 130.14 0.02 2019.56 5.24 10.3 10 2 19250+1157 STT 588AB 280.7 0.05 108.27 0.10 2019.56 5.24 8.65 20 4 19250+1157 STT 588AC 276.6 0.06 151.58 0.15 2019.56 5.24 10.34 20 4 19250+1157 STT 588BC 266.5 0.04 44.49 0.04 2019.56 8.65 10.34 20 4 19254+2542 ARY 17 267.9 0.07 115.97 0.10 2019.64 8.31 8.72 15 3 20065+1253 HJ 1476 73.1 0.04 12.31 0.02 2019.63 9.7 10.7 15 3 20095+4752 BLL 45 139.5 0.02 145.37 0.10 2019.63 9.01 9.92 15 3 20131+3411 STTA203 36.9 0.03 88.37 0.10 2019.67 8.26 9.14 15 3 20168+3731 ARY 25 293.1 0.04 147.14 0.10 2019.63 8.65 8.72 15 3 20234+3053 ARG 91 175.4 0.05 20.75 0.03 2019.63 8.59 9.48 15 3 20248+1452 STF2680 287.8 0.03 16.21 0.02 2019.65 9.20 9.48 15 3 20332+4028 HJ 609 320.2 0.04 26.67 0.02 2019.63 8.84 9.34 15 3 20348+0514 SCJ 26 88.4 0.04 25.11 0.03 2019.65 8.49 10.13 15 3 20371+3837 SEI1193 353.0 0.06 17.06 0.03 2019.65 8.76 10.1 15 3 20413+2922 ARY 29 142.7 0.03 119.29 0.10 2019.63 8.10 8.46 15 3 20433+4456 ES 2699 296.4 0.05 40.05 0.03 2019.66 8.64 9.51 15 3 20459+4448 ES 2701 80.8 0.03 50.94 0.02 2019.70 8.76 9.24 15 3 20520+6022 SKF2091 291.5 0.04 45.37 0.03 2019.63 8.69 9.87 15 3 20582+0447 AG 268 286.9 0.05 12.54 0.01 2019.68 8.59 9.99 15 3 20583+0831 ARY 87 214.9 0.03 62.18 0.03 2019.68 8.24 9.85 15 3 20584+0757 ARY 68 339.1 0.03 112.40 0.09 2019.68 8.80 9.30 15 3 21090+0643 STT 428 255.7 0.06 24.01 0.03 2019.63 8.41 9.93 15 3 21122+5854 ARG 107 192.6 0.04 37.02 0.03 2019.63 8.16 9.24 15 3 21183+4244 HJ 1634 143.1 0.02 28.88 0.03 2019.68 9.32 9.53 15 3 21314+4829 ARN 78 100.9 0.02 50.04 0.03 2019.63 7.64 8.82 15 3 21346+5906 STF2810 290.1 0.03 16.82 0.01 2019.68 8.43 9.04 15 3 22110+3024 DAM1271 79.7 0.03 34.69 0.03 2019.68 9.3 9.5 15 3 22112+2335 ARY 63 189.0 0.02 92.44 0.07 2019.80 9.68 10.14 15 3 22120+3739 STF2876 68.6 0.08 11.75 0.02 2019.63 8.06 9.81 15 3

Table 1 (continued). Results of 206 double stars using the video drift method. Table continues on the next page.

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 147

Double Star Measures Using the Video Drift Method - XIII

Discover PA Sep. Avg. Position PA Sep. Mag 1 Mag 2 Drifts Nights Code SEM SEM Date 22152+4953 STF2890AB 11.1 0.03 9.42 0.01 2019.80 9.42 9.71 20 4 22152+4953 STF2890AC 277.5 0.03 73.12 0.03 2019.80 9.42 9.40 20 4 22221+0045 ARY 30 339.6 0.01 119.94 0.05 2019.63 8.69 9.24 15 3 22338+0352 GRV 587 229.4 0.04 77.88 0.06 2019.87 9.72 9.98 15 3 22375+3855 STF2926 334.8 0.04 21.58 0.04 2019.64 9.10 9.54 15 3 22387+3718 AG 284 229.8 0.07 26.45 0.03 2019.64 9.86 9.94 15 3 22451+3841 HDS3229 330.1 0.05 19.84 0.03 2019.87 8.56 10.66 15 3 22485+4524 ARN 99 228.6 0.03 37.48 0.05 2019.67 8.42 10.42 15 3 22487+3818 AG 288 186.3 0.04 18.70 0.03 2019.87 8.93 10.36 15 3 22530+3140 HJ 972 208.0 0.05 28.64 0.03 2019.80 9.64 10.71 15 3 23029+4610 HJ 1841AB 344.2 0.05 18.15 0.02 2019.80 9.69 10.18 15 3 23029+4610 HJ 1841AC 285.2 0.06 33.59 0.02 2019.80 9.69 10.42 15 3 23065+4655 STTA242 31.0 0.03 79.95 0.06 2019.76 7.75 8.57 30 3 23169+4238 HJ 1864 205.4 0.04 22.87 0.02 2019.80 9.79 10.35 15 3 23188+0510 STF2999AB 166.8 0.02 78.90 0.07 2019.80 8.90 9.17 20 4 23188+0510 STF2999AD 19.1 0.04 27.40 0.03 2019.80 8.90 11.9 20 4 23188+0510 STF2999BC 171.9 0.05 9.78 0.02 2019.80 9.17 10.86 20 4 23207+4848 ARY 3AB 210.7 0.04 120.46 0.08 2019.87 8.96 9.47 15 3 23231+4501 SCA9004 107.1 0.05 79.48 0.03 2019.87 8.35 9.39 15 3 23428+4727 ES 548 316.0 0.07 14.25 0.01 2019.87 9.23 10.19 15 3 23530+4121 ARG 108 147.5 0.03 52.98 0.06 2019.87 7.15 9.46 15 3 23593+5352 ES 2736 107.7 0.03 19.47 0.01 2019.80 9.07 10.50 15 3

Table 1 (conclusion). Results of 206 double stars using the video drift method.

Table 1 Notes: • All magnitudes taken from the WDS catalogue. All position angle/separation measurements are for the Equator and Equinox of date. • “SEM” is the Standard Error of the Mean. See the text for the definition and usage. The column “Drifts” is the number of separate measurements made using both the drift and modified drift methods. “Nights” is the number of nights’ drift runs were made for that system.

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 148

Astrometry of WDS 13472-6235

Emily Gates1, Brighton Garrett1, Phoebe Corgiat1, Marissa Ezzell1, Jon-Paul Ewing1, and Richard Harshaw2

1. Paso Robles High School, CA 2. Institute for Astronomical Research (InStAR)

Abstract: Double star system WDS 13472-6235 was observed and analyzed with images taken using the Las Cumbres Observatory 0.4-m telescope at the Cerro Tololo Observatory. The stars were found to have a separation of 9.30" and a position angle of 318.01°. This star does not currently have an orbit calculated and the data we found in our observations was collected in order to help somebody else calculate an orbit in the future. As it stands now, it is undecided as to whether or not WDS 13472-6235 is truly physical or is an optical system.

Introduction A group of four students from Paso Robles High School (Figure 1) came together through the school’s Field Studies Collaborative: Astrometry Research Sem- inar with the goal of observing the double star, WDS 13472-6235 (Figure 2). The goal of this group was to contribute data so that future observers could better understand the system and have the resources to potentially determine the nature of the double star and find its potential orbit. Since its initial discovery in 1897 by the Cordoba Observatory, this double star has only been observed eight times. The previous most recent observation of Figure 1. Team Alcor in front of the 60” telescope at the WDS 13472-6235 was in 1998. The team chose this Mount Wilson Observatory double star since it had so few observations and had not been observed in so long. The spectral class of the star is G8Ia, meaning that it is a yellow supergiant. The magnitude of the primary star is 7.19 and the magnitude of the secondary star is 9.9 producing a difference in magnitude of 2.71. WDS 13472-6235, located in the Centaurus constellation, is a quadruple system in which only the aforementioned primary and secondary stars are visible using ground- based telescopes. Equipment and Procedures The images used to gather data in this study were Figure 2: Image of WDS 13472-6235 taken from LCO’s 0.4-m taken through the Las Cumbres Observatory (LCO) telescope at the Cerro Tololo Observatory

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 149

Astrometry of WDS 13472-6235

Discussion In AstroImageJ an aperture radius of two was selected as it fit the smaller star in the pair seen in all of the images. There were a few outliers when the data was first calculated, but after uploading the image again to AstroimageJ and allowing the program to calculate the radius, the data corrected itself in the program and we removed the remaining outliers. It was also noted that the exposure time of the image had no correlational results on the data. When analyzing the data that was collected, we used the Excel Spreadsheet Plotting Tool 3.10 created and described by Richard Harshaw (2018) to create a plot graph that will eventually lead to an orbital plot. (Figure 3) The data collected by our team follows the trend of past data. While analyzing the data, though, we decided to reject some of the past observations due to them being outliers; those particular data points did not follow the trend line of all of the data acquired over the years. The past observations that were omitted were taken from Chesneau (2014), which observed the stars Aa and Ac, and from the Hipparcos satellite, which observed Figure 3. Plot of the historical measurements of 13472-6235 Aa and Ab. These points were omitted because our AB (green diamonds) with our data point shown by the red tri- team wanted to calculate the distance between the two angle; this data will eventually lead to a calculated orbital larger stars, A and B. plot. Units on X and Y axis are in arc seconds. The parallax the GAIA satellite reported back to us was deemed unreliable since the parallax was less than Global Sky Partners program (2019); the LCO tele- 5 milliarcseconds. scope used to acquire these images was at the Cerro Tololo Observatory located in Region IV, Chile. At this Conclusion location, an SBIG STL-6303 camera on a 0.4-m tele- The objective of this research was to acquire more scope was used to take 28 images of WDS 13472-6235 data on the separation and position angle of the double at three different exposure times: 0.5 seconds (10 imag- star WDS 13472-6235 while also gaining experience in es), 1 second (9 images), and 2 seconds (9 images). The the field of Astrometry. The results collected by our exposure lengths were determined by the magnitude of team proved to be consistent with previously collected the primary star (7.19). data, but no further conclusions can be made on the Using the program AstroImageJ (Collins, et al. orbit of the stars or if the pair is an optical double or 2017), the team analyzed the acquired images to find true binary system due to the overall lack of data at the position angle and separation of the pair for all 28 hand. images. To accomplish this, an aperture radius of two Acknowledgements was selected for the measurements on all the images. We would like to thank Cora Karamitsos, Rachel The averages and errors in the results were then calcu- Freed, and Rick Wasson for editing and giving sugges- lated. The team’s averaged data point and the data tions for our paper; Karen Collins for developing As- points from past observations were then plotted in Fig- troImageJ, the tool we used to calculate our results; Bri- ure 3, which shows the change in the position of the an Mason for supplying us with historical data on our stars relative to one another within a cartesian coordi- star from the US Naval Observatory, which allowed us nate system. to compare our results to past observations; Dave Rowe Results and his GDS (GAIA Double Star) Selection Tool that The position angle was calculated to be 318.01° helped us choose which star to observe; and finally, and the separation to be 9.30 arc seconds. The observa- Rachel Freed, Jimmy Ray, and all of the professionals tions were taken on April 17th, 2019 and are displayed who helped and supported us through this experience, in Table 1. we wouldn’t have been able to do this without all of

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 150

Astrometry of WDS 13472-6235

Exp. Time (s) 0.5 1 2

Image Number PA (deg) Sep (as) PA (deg) Sep (as) PA (deg) Sep (as)

1 317.77 9.41 318.05 9.21 318.84 9.18

2 318.24 9.38 317.97 9.26 318.29 9.30

3 317.68 9.33 318.38 9.38 318.72 9.22

4 317.28 9.31 317.59 9.25 318.30 9.23

5 317.71 9.27 317.37 9.33 317.71 9.30

6 318.10 9.45 317.98 9.33 319.02 9.24

7 318.11 9.19 318.46 9.38 318.65 9.21

8 318.08 9.21 317.86 9.19 318.10 9.24

9 317.06 9.46 318.12 9.39 317.08 9.43

10 317.68 9.37 - - - -

Mean 317.77 9.3438 317.98 9.303 318.30 9.261

Std. Dev. 0.38 0.093 0.34 0.076 0.61 0.074 Std. Err. of 0.12 0.029 0.16 0.025 0.20 0.025 Mean Avg of all 3 PA (deg) Sep (as) exposures Mean 318.01 9.30

Std. Dev. 0.49 0.085 Std. Err. 0.093 0.016 of Mean Table 1: Separation and Position Angle for all 28 images measured using AstroImageJ

you. This work makes use of observations from the ESA, 1997, The Hipparcos and Tycho Catalogues, ESA LCO Network Global Sky Partners Program. This re- SP-1200. search has made use of the Washington Double Star Global Sky Partners | Las Cumbres Observatory. (n.d.). Catalog maintained at the U.S. Naval Observatory. Retrieved August 5, 2019, from https://lco.global/ References education/partners/ 13472-6235 COO 157AB (V766 Cen). (n.d.). Retrieved Harshaw, R, 2018, “Gaia DR2 and the Washington April 29, 2019, from https://www.stelledoppie.it/ Double Star Catalog: A Tale of Two Databases”, index2.php?iddoppia=57963. JDSO, 14 (4), 734-740. Chesneau, O., Meilland, A., Chapellier, E., Millour, F., “Many Eyes - One Vision: Las Cumbres Observatory.” Genderen, A. M. van, Nazé, Y., … Vanzi, L., 2014, Many Eyes - One Vision | Las Cumbres Observato- “The yellow hypergiant HR 5171 A: Resolving a ry, lco.global/. Retrieved April 16, 2019, from massive interacting binary in the common envelope https://lco.global/ phase”, A & A, 563, A71, https:// doi.org/10.1051/0004-6361/201322421. Rowe, D. A., personal correspondence Collins, K., Kielkopf, J., Stassun, K, and Hessman, F., 2017, “AstroImageJ: Image processing and photometric extraction for ultra-precise astronomical light curves”, A J, 153:77, 13pp.

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 151

A New Opportunity for Speckle Interferometry on the Mount Wilson 100-inch Telescope

Rick Wasson1, Reed Estrada2, Chris Estrada2, Richard Harshaw3, Jimmy Ray4, Dave Rowe5, Russ Genet6, Rachel Freed7, Pat Boyce7 8, and Tom Meheghini9

1. Orange County Astronomers, Murrieta, California 2. Institute for Student Astronomical Research (InSTAR), Lancaster, California 3. Brilliant Sky Observatory, Cave Creek, Arizona 4. Arizona Sonoran Desert Observatory, Glendale, Arizona 5. PlaneWave Instruments, Rancho Dominguez, California 6. California Polytechnic State University, San Luis Obispo, California 7. Institute for Student Astronomical Research (InSTAR), San Francisco, California 8. Boyce Research Initiatives and Education Foundation (BRIEF), San Diego, California 9. Mount Wilson Institute, Pasadena, California

Abstract: Speckle interferometry observations were made by a group of students from Paso Robles High School on the Mount Wilson 100-inch Hooker Telescope - the first time that high school students have made scientifically useful observations with it. This field trip was supported by InSTAR educators and amateur speckle observers. This paper describes the “Engineering Test Run” which was conducted to check whether amateur speckle equipment could be successfully used on the large telescope, to help ensure success of the student observations. All goals of this Engineering Test were accomplished. The close binary stars STT 269AB and A 570 were observed in multiple filters. Autocorrelation and BiSpectrum Analy- sis astrometric and delta magnitude results are presented.

Introduction galaxies far from the Milky Way, and for initial realis- The iconic 100" Hooker Telescope is one of the tic measurements of the scale and expansion of the uni- most famous and historically significant science instru- verse. Although no longer used for deep-sky studies ments of the twentieth century, but it is not widely because of the lights of millions of people living in the known that Mount Wilson Observatory has been the cities below, Mount Wilson is still an excellent site for site of high-resolution astronomy for a full century. In the study of bright objects. 1919 J.A. Anderson built a visual interferometer for the The Speckle Interferometry technique, proposed 100" telescope, using it to measure, for the first time, and demonstrated by Antoine Labeyrie in the early the orbit of a spectroscopic binary star - the bright near- 1970’s and developed for binary stars by McAlister by star Capella, separation about 0.05" (Anderson, 1920 (1977), was first used by professional astronomers on and Merrill, 1921). This landmark achievement proved the 100" in 1985. The 100-inch was closed from 1985 that the new interferometry technique actually works on to 1993 but since then it has again been used for speck- stars, making way for the famous 20-foot interferome- le observations by several professional teams (Hartkopf ter on the 100", with which the size of a star - Betel- et al. 1997). Because the 100" mirror has no central geuse – was first measured (Michelson & Pease, 1921). hole, the Cassegrain focus was located high off the Several other ground-breaking interferometry research floor, awkward even for professional speckle observers. projects have utilized the excellent seeing at Mount In the last several years the 100" has begun a new Wilson, culminating in the current CHARA array life in astronomy public outreach. As part of that out- (McAlister, et al. 2005). reach, a safe, accessible location for public viewing was The 100" telescope is best known for Hubble’s fa- needed on the main floor level, to eliminate the high mous discoveries that the spiral nebulae are separate ladders and platforms used by past observers. A new

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 152

A New Opportunity for Speckle Interferometry on the Mount Wilson 100-inch Telescope

trip. Therefore, a team of amateurs and teachers were invited to mentor the students, giving them “hands-on” training in observational science. This paper supple- ments details that the students didn’t have time to learn on the mountain or include in their accompanying paper (Gates, et al. 2020b). The Support Team In conjunction with InSTAR, a group of amateur speckle observers and teachers came together to support the PRHS field trip. The team proposed an “Engineering Test Run” to see whether the combination of available speckle instrumentation would work on a large telescope. Mount Wilson Executive Director Figure 1. Students got a day-time orientation tour of all the historic telescopes and history of Mount Wilson. The 100” Tom Meneghini graciously offered to host the team on Cassegrain relay optics is the white tube below the massive the 100" for an evening checkout, to help ensure that blue mirror cell. Portraits of Edwin Hubble and Mount speckle observations with amateur equipment never Wilson Observatory founder George Ellery Hale look on. before used on such a large telescope, would be successful for the students. system of relay optics now brings the Cassegrain focus The goals of the Engineering Test, conducted on down below the primary mirror for safe, convenient June 7, 2019 were: public access. • Reach focus on the science camera, when mounted on the relay optics at the public focal point. New Opportunities • Evaluate telescope pointing and slow-motion con- Recent developments have made speckle interfer- trols for finding and centering target stars in the ometry accessible to non-professionals at Mount Wil- very small camera field. son: (1) the 60" and 100" telescopes are open to ama- • Demonstrate the practicality of Drift Calibration teur and student observers on a fee basis; (2) new sensi- with very long focal length. tive high-speed cameras and free analysis software have • Develop and practice communication and coordi- made speckle interferometry practical and affordable nation procedures with the Telescope Operator. for amateurs and students. • Identify workstations and observing tasks for stu- The Paso Robles School District in central Califor- dent involvement and participation. nia has an outstanding science field trip program, sup- • Demonstrate accurate speckle measurement of a ported by generous private grants. In 2018 a group of close double star. Paso Robles High School (PRHS) students came to Mount Wilson for a history-geology-ecology- While Tom Meneghini operated the telescope, environment-astronomy field trip, viewing the sky with Reed and Chris Estrada used the fine guidance controls their own eyes through the 100" telescope. for finding and centering, and Rick Wasson ran the In June 2019, a new group of eight PRHS students speckle camera through a laptop computer. We suc- in the Astrometry Field Research Program, in collabo- cessfully accomplished all the goals of the Engineering ration with the Institute for Student Astronomical Re- Test, including demonstrating repeated calibration search (InSTAR), completed observations, analysis and drifts, and measuring Separation and Position Angle of draft write-ups for two southern double stars, remotely two close binary stars (i.e., separation much smaller observed with robotic 0.4-meter telescopes at Las Cum- than the “seeing disk”), in four filters. bres Observatory (Gates, et al. 2020a and Hughes, et al. The rest of the support team gathered a week later 2020). These students enjoyed docent-guided tours of with the students to guide them through the speckle the mountain’s environment, facilities and history, Fig- observations, Figures 2, 3 and 4. At the end of the ure 1, just like the 2018 group. But this research group evening, everyone got the bonus of looking through the came to Mount Wilson with an added goal: to observe great telescope, Figure 5. close double stars with the 100" telescope using the Speckle Interferometry technique. Speckle Instrumentation The PRHS students had no opportunity for training The camera optical train of Figure 6 consisted of a or experience in speckle interferometry before the field two-inch Vixen flip mirror attached to a ZWO five sta-

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 153

A New Opportunity for Speckle Interferometry on the Mount Wilson 100-inch Telescope

tion 1¼ inch electronic filter wheel. This was attached on the straight-through port to the ZWO ASI1600 cooled monochrome science camera, on loan from Dave Rowe. A 23 mm illuminated cross hairs eyepiece was on the flip port, for a wider field to locate and center targets when a slew put the star outside the field of view of the science camera. No Barlow was used for extra magnification; the 100"” f/11.5 relay optics and camera 3.8 μ pixels were estimated to give adequate sampling (4 to 5 pixels across the Airy disk) for initial speckle checkout. Elim- inating the Barlow gave the largest field available for finding target stars (about 125 arc-sec wide), and the longest calibration drifts possible (about 8 seconds). Figure 4. The students got a behind-the-scenes tour of the Several standard photometric, photographic and 100" RA worm drive gear from Mount Wilson Executive Di- near-IR long-pass filters were used for the 100" obser- rector Tom Meneghini vations, with the characteristics shown in Table 1. All the filters are of the modern interference type. The

Figure 5. After speckling, everyone looked through the 100". Figure 2. Dave Rowe gave the students an introductory lecture on Speckle Interferometry before dark.

Figure 6. Speckle Optical Assembly. Left-to-Right: Focus- Figure 3. During student speckle observations, the camera er, Flip Mirror (1¼-inch reticle eyepiece pointing down), view was routed to a large monitor for all to see. Science Filter Wheel, and ZWO ASI1600MM Pro camera. Cables teacher and field trip leader Jon-Paul Ewing described the control Peltier cooling, USB3.0 camera interface, and filter procedures, as the amateurs operated the camera. wheel.

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 154

A New Opportunity for Speckle Interferometry on the Mount Wilson 100-inch Telescope

Photometric Wavelength Width Manufacturer Type Filter System (nm) (nm) Johnson Astrodon Interference B 435 80

Johnson Astrodon Interference V 542 90

LRGB Baader Interference R 634 105

Sloan Astrodon Interference i’_2 753 160

none Astronomik Interference IR807 862 200

Table 1. Characteristics of the filters used for the Speckle Engineering Run and the Paso Robles Student Run

equivalent “Wavelength” is for the convolved characteristics: i.e., the weighted average of filter transmission times QE of the CMOS detector. The “Width” column of Table 1 is for 50% transmission, but for the IR807 long-pass filter, the long side is determined by the CMOS Silicon detector sensitivity limit (assumed to be 1000 nm), rather than the filter transmission. A clear (luminance) filter in the first position was used for initial target acquisition and centering. In the Engineering Run, the B, V, i’ and IR807 filters were used; for the Student Run, the R filter was substituted for IR807. Figure 7. The 100" observing floor. The Telescope Opera- Target Selection tor station is located on the upper level, left of the stairs. A Target List was prepared in advance of the observations. Since the resolution of the 100" telescope, about 0.06" at 600 nm, is much better than usually (2) Fine Guidance station for small movements to available to high school students and amateur astrono- find and center the star, located near the telescope fo- mers, close doubles were targeted. The WDS Catalog cus; was searched, using the search tool WDS1.2 (Rowe, (3) Camera Operator station, a laptop computer on 2017), for a separation range of 0.0" to 0.5", RA near a movable table under the telescope, connected by ca- the meridian on June evenings, and declination ±20 bles to the speckle instrumentation, for control of the degrees from the Mount Wilson latitude (+34 degrees). camera, Peltier cooler and filter wheel. From the very large list of possible candidates, priority A “Target Card” was filled in with Double and Ref- was given to known binaries having an estimated orbit erence star information, including SAO number, which needing more speckle observations, and doubles that is the easiest way for the Telescope Operator to com- may include a red dwarf. mand the 100" to the target. This card was taken to the For the Engineering run, a few stars with a separa- T.O. station, located up a stairway above the observing tion range of 0.1"-0.4" were chosen, to evaluate the ca- floor, shown in Figure 7. Communication between the pabilities of the new speckle system. Single reference T.O. and observers below was through a built-in, porta- stars for deconvolution were chosen from the list of ble “Comm Box” system located near the focal point. nearby SAO stars, also provided by the WDS1.2 pro- On request from the Camera Operator, the T.O. gram. moved the telescope to the next target. Often the star Observing Procedures appeared in the camera field of view (FOV), as seen in Three stations were necessary for telescope control Figure 8. Sometimes the star passed slowly through and data acquisition: and stopped just outside the FOV. If the star was not (1) Telescope Operator (T.O.) station, from which found, the telescope was moved by slow-motion con- the telescope was slewed to the target; trols located near the focus, while watching through the

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 155

A New Opportunity for Speckle Interferometry on the Mount Wilson 100-inch Telescope

Figure 8. Example of the FireCapture display of the camera Figure 9. Several of the authors watch the highly magnified FOV, showing a star being centered. speckle camera images as 1000 frames are automatically recorded in each of four filters.

wider-FOV eyepiece of the flip mirror. for the folder names in which the images were stored. After the target was found and centered, the focus, Although not needed in the Engineering Test, a flat filter and camera settings were double-checked, and a screen television was attached to the laptop computer 600x600 pixel Region of Interest (RoI) was drawn for the Student Run to allow everyone to watch the data around the star. Then recording was started for a se- collection. This allowed information and participation quence of 1000 images in each of the four filters, with- by the other student team members manually recording out further intervention (Figure 9). FireCapture com- the sequence numbers and providing target information municated with the filter wheel under ASCOM proto- to the telescope operator. cols (Denny, 2019), automatically moving the filter wheel to the next filter before each new 1000-frame Software sequence. The speckle images were saved as 16-bit Before the Engineering run, a list of close double FIT files; the camera only provides 12-bit output, but stars suitable for resolution of the 100" aperture was FireCapture fills the least-significant-bits with zeros to assembled using the “WDS1.2” program (Rowe, 2017). create standard FIT files. This utility program searches the WDS Catalog to as- After the first double star was recorded, the tele- semble a list of all doubles within the user-input param- scope was moved to its Reference star, but it was not eters; it also provides a list of all SAO Catalog stars seen in the camera or eyepiece field. After an extended within 3 degrees of the double, from which an appropri- but unsuccessful manual search, it was decided to move ate Reference star can be chosen. on to the next target. A series of Calibration Drifts was The “FireCapture” program (Edelmann, 2017) was then done for this close double star, in case the same used for data acquisition. It is available on his website, problem might occur again for its Reference star. wonderplanets.de. This program, designed for planetary Double stars which are closer than the seeing disk photography, features automatic telescope, camera, and may generally be used for drift calibration, because filter wheel control, and flexible file naming. It can each image is used independently, and the two compo- save images in several formats including FIT files, the nents have very little effect on the centroid of the see- standard image format for astronomy, required by STB. ing disk. However, a double with components wider All speckle processing and analysis made use of the than the seeing, particularly if they are similar in bright- “tools” in the “Speckle Tool Box” (STB) program ness, should not be used, because the centroid may shift (Harshaw, Rowe and Genet, 2017). The “Drift Calibra- back and forth between components in successive tion” tool automatically analyzes a sequence of short- frames, creating unnecessary noise in the drift path. exposure images, in which the star moves across the After completing an observation, entries were made frame at the sidereal rate while the telescope RA drive in an Observing Log, which was simply a copy of the is turned off. The tool uses star declination and com- Target List spreadsheet. Log entries included date, star, puter time of each image, written to the FIT header by filter and Sequence number - an identifier for each se- FireCapture, to calculate the average pixel scale and quence of frames recorded, which is automatically in- slope (camera rotation angle) for each drift sequence. cremented by FireCapture. This Log acted as backup Speckle Autocorrelation (AC) analysis was pro-

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 156

A New Opportunity for Speckle Interferometry on the Mount Wilson 100-inch Telescope

cessed in “STB1.05,” using the “Make FITS Cubes,” Fortunately, Drift Calibration worked very well, “Process FITS Cubes,” and “Speckle Reduction” tools. and was easier than expected on the 100". The cam- Double star Position Angle (PA) and Separation (ρ) are era’s wider dimension was first roughly aligned with the astrometry products of AC measurement. the E-W direction by moving a star back and forth Bispectrum Analysis (BSA) processing was done in across the FOV with the slow-motion controls. An ROI “STB1.13” (Rowe and Genet, 2020). The goal of BSA was drawn having full width (4656 pixels), but only is to reconstruct a near-diffraction-limited image of the about 400 pixels in height; this narrow ROI was neces- double star, in which the PA 180-degree ambiguity, sary to minimize frame size and write time, thus in- always present in AC, is removed. BSA also recovers creasing the number of frames recorded during each the proportional flux of each component, so approxi- drift. About 80 frames were recorded in each drift, last- mate delta magnitude can be extracted by aperture pho- ing about 9 seconds for a star at +26 degrees declina- tometry. tion. If a single Reference (deconvolution) star is ob- To prepare for each drift, the star was positioned at served, it can be used for both AC and BSA processing, the eastern edge of the ROI band. A “3-2-1-stop” greatly improving the results by cancelling optical and countdown was called over the intercom, the T.O. atmospheric distortions which are common to both the stopped the telescope RA drive, and the camera record- Double and Reference star images. ing was begun. When the star reached the western edge of the field, the T.O. was requested to re-start the RA Drift Calibration drive, and camera recording was stopped. Although it Calibrations for pixel scale and camera rotation had drifted out of the FOV, the star was easy to recover angle relative to the sky are essential for accurate as- by simply driving the telescope slow-motion control trometry. Observation of well-known double stars is a back to the west for the next drift; there was no declina- method often used for speckle instrumentation perma- tion shift that might have caused the star to miss the nently mounted on an equatorial telescope. However, camera FOV. the Engineering and student observations were only Several drifts were completed in a few minutes so short-term projects for observation of relatively few that temporary, random seeing-induced wandering of objects. A two-slit aperture mask, based on Young’s the star from the true E-W direction could be averaged. interference principles, has been used for speckle cali- It was a great relief that the Drift Calibration technique bration on the 100" by professionals in the past (Genet, was successful and easy to do with a telescope of such et al. 2016). It is still available but is cumbersome and long focal length; a camera with a much smaller sensor time-consuming to install and remove. would have made it much more difficult. Drift calibration, commonly used with small tele- For Drift Calibration, STB calculates the centroid scopes by amateur speckle observers, is relatively easy, of the brightest star image in each frame, in the camera fast and accurate. However, to our knowledge, it has pixel reference system. It also reads the computer not been used before on such a large telescope of long clock time for each frame, written to the FIT header focal length (100" f/11.5, FL~29m). We assumed it during recording. The times do not need to be accurate would be impractical for our small CMOS cameras, (GPS), but only self-consistent during the brief drift. because of the extremely small FOV and short time for The sequence of drift centroids and times, plus the sidereal drift across the field. For example, the ZWO star’s declination, provide all the information required ASI290M camera FOV would be only 40 arc-sec wide, for calibration of both camera angle and pixel scale. giving less than 3 seconds of drift time for a star at the An example of the STB screen display for one Engi- celestial equator. neering drift is seen in Figure 10. As part of planned automation capability for Results of all 5 drifts are shown in Figures 11 and PlaneWave telescopes, Dave Rowe had already pur- 12. The famous Mount Wilson seeing was very good chased a ZWO ASI1600M-Pro camera, and kindly that night, as verified by the excellent agreement and made it available for the Mount Wilson speckle effort. small standard deviations of the 5 drifts. Generally, it The sensor of this camera is 18mmx13mm, more than 3 is better to use the average of 10 or more drifts for cali- times larger than the 290. With this camera the 100" bration. FOV is over 2 arc-minutes wide, yielding a drift time STB works only in the camera pixel row-column over 8 seconds at the equator; longer drifts occur at reference system, unaware of sky directions in advance. higher declination. Successful demonstration of the Therefore, actual PA must be verified or corrected by Drift Calibration technique was one of the primary the user. STB subtracts the calibrated camera orienta- goals of the Engineering run. tion angle (1.46o in our case, Figure 11) from the PA

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 157

A New Opportunity for Speckle Interferometry on the Mount Wilson 100-inch Telescope

measured in the camera reference system. The actual orientation of the camera was North-up and East-right, as seen in Figure 13 at left. East and West were reversed from the sky view, evident by the star drifting right-to-left in the calibration drifts. This was caused by an odd number of reflections (5) in the complete optical path: primary, secondary and tertiary mirrors in the Cassegrain configuration, plus two additional reflections in the relay optics. The secondary stars of both binaries observed in the Engineering run were expected to be in the southwest quadrant (PA 180- 270). However, in the camera field, they appeared as the mirror image, in the lower left quadrant (apparent PA 90-180), and STB measured PA in that quadrant. Figure 11. Drift Calibration Results for Camera Angle. Therefore, PA was corrected for East-West reversal using the equation

PAcorrected=−360 PA STB as illustrated in Figure 13.

Figure 12. Drift Calibration Results for Pixel Scale.

Figure 13. Binary star A570 re-constructed BSA image, in the V filter. At Left: Camera view in STB has north-up and east-right, a mirror image of the sky view, caused by an odd number of reflections in the optical train. STB measured Figure 10. Screen Shot of one STB Drift Calibration se- o PASTB ~ 126 . At Right: Corrected PA orientation with north quence. Blue points are greater than 3-σ, which were not in- o -up and east-left. PAcorrected ~ 234 , consistent with the sky cluded in the linear regression. o view and orbit ephemerides PA ~ 237 .

WDS Discovery Mag1 Mag2 Del V Spectrum Period Grade PA Sep 13329+3454 STT 269AB 7.27 8.08 0.81 A6III 53 2 227 0.30 14323+2641 A 570 6.61 7.08 0.47 A6V 30 1 237 0.19 Table 2. WDS characteristics of the two double stars observed during the Engineering Test Run 7 June 2019. The columns are: WDS RA and Dec, WDS discovery designation, WDS magnitudes of primary and secondary components, WDS delta magnitude, WDS spectral type, Period (years) from WDS 6th Orbit Catalog, orbit grade, and PA and Separation ephemerides for 2019.5.

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 158

A New Opportunity for Speckle Interferometry on the Mount Wilson 100-inch Telescope

Results Two bright double stars were observed during the Engineering Run on June 7, 2019. Their WDS characteristics are summarized in Table 2. The WDS orbit plots are shown in Figures 14 and 15. Our new astrometric observations are presented in Table 3. Two methods of speckle data processing, both Autocorrelation (AC) and BiSpectral Analysis (BSA) as noted above, were performed for each of the four filters, giving a total of 8 measures for each star. Alt- hough the AC and BSA methods used the same original sequences of 1000 speckle frames, different processing always produces slightly different results; they were treated as independent measurements for calculation of the average and standard deviation shown at the bottom of Table 3 for each star. Table 3 also provides BSA delta magnitudes in each filter. These ΔMag results are considerably small-

er than the WDS magnitudes of Table 1, which are Figure 14. The WDS orbit plot of STT269AB. The larger probably V magnitudes. This is true even for the John- yellow circle is the average of the new measurements from son V filter used here. Table 3, and the two smaller yellow circles are the farthest Figures 16 and 17 show AC and BSA images for outliers. the binary stars 13329+3454 STT269AB and 14323+2641 A570, respectively. Discussion The 100" Cassegrain focus, modified with relay optics for public access, now has a focal ratio of f/11.5, and can accommodate 2-inch or 3-inch eyepieces. Be- fore the Engineering run, there was concern about whether the 2" speckle optical train could easily be mounted and brought to focus. However, minor movement of the tertiary mirror gave plenty of focuser travel, and there is still more tertiary travel available if needed in the future. The famous Mount Wilson seeing was excellent on the night of the Engineering Test. Ideal weather often occurs in the Spring, when marine clouds blanket Los Angeles below, and cool, calm air flows gently over the mountain. An outside walk at midnight revealed a dark sky, bright Milky Way, no breeze, and no twinkling of the stars! Double star targets were purposely chosen within Figure 15. The WDS orbit plot of A570. The yellow circle is o o the average of the new measurements, and all 8 AC, BSA about 20 of the Mount Wilson latitude (+34 ) and were and filter measurements of Table 3 lie within it. observed within about one hour of the meridian, to avoid extreme telescope orientation, high airmass and mally used on the 100" to locate targets visually. The atmospheric dispersion; but the B filter BSA images in flip mirror has a 2" nose piece but M42 T-thread on Figures 16 and 17 still have more distortion than at both output ports; no adapter was available for mount- longer wavelengths. ing a 2-inch eyepiece. Therefore, a 1¼ inch 23mm illu- With the very long focal length (over 29m), even minated eyepiece was used, giving a FOV only slightly the “big” sensor (17.6mm x 13.4 mm) of the ZWO larger than that of the camera. Nevertheless, the tele- ASI1600M camera gave a field of view (FOV) only scope pointed very well, landing the target star in the about 2 arc-minutes wide. A 2-inch 55mm eyepiece having more than twice the FOV of our camera is nor- (Text continues on page 160)

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 159

A New Opportunity for Speckle Interferometry on the Mount Wilson 100-inch Telescope

WDS Discovery Method Filter PA Sep ΔMag 13329+3454 STT 269AB AC B 220.48 0.280 BSA 220.95 0.286 0.20

AC V 222.51 0.296 BSA 223.04 0.295 0.09

AC Sloan i’ 222.53 0.295 BSA 221.22 0.287 0.14

AC IR807 222.61 0.295 BSA 220.73 0.291 0.07 Average 221.76 0.291 Std Dev 1.01 0.006 14323+2641 A 570 AC B 233.76 0.181 BSA 235.78 0.186 0.39

AC V 234.12 0.180 BSA 234.79 0.180 0.24

AC Sloan i’ 234.02 0.179 BSA 233.96 0.185 0.22

AC IR807 234.04 0.178 BSA 235.44 0.181 0.15 Average 234.49 0.181 Std Dev 0.76 0.003 Table 3. Speckle measurements, using the Mount Wilson 100" Telescope, ZWO ASI1600M Pro CMOS camera, and interference filters, on Besselian date 2019.433. The columns are: WDS RA and Dec, WDS discovery designation, Method of speckle data analysis (Autocorrelation or BiSpectrum Analysis), filter (Table 1), Position Angle (deg), Separation (arc-sec), and BSA Delta magnitude (secondary-primary).

Johnson B Johnson V Sloan i’ IR807

Figure 16. 13329+3454 STT269AB Autocorrelations (above) and reconstructed BSA images (below). The images are oriented North-up, East-left, as on the sky. No Reference star was observed.

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 160

A New Opportunity for Speckle Interferometry on the Mount Wilson 100-inch Telescope

Johnson B Johnson V Sloan i’ IR807

Figure 17. 14323+2641 A570 Autocorrelations (above) and reconstructed BSA images (below). The orientation is North-up, East-left, as on the sky. Reference star SAO 83321 was observed and used in both AC and BSA processing

(Continued from page 158) camera FOV for the next drift. Drift Calibration should camera FOV most of the time. be seriously considered by future speckle observers. Centering the star on the illuminated cross hairs of The ZWO electronic filter wheel was controlled by the flip mirror eyepiece always placed the star near the FireCapture with ASCOM protocols. Once a speckle center of the camera field, within the pre-selected ROI. sequence was started, the program recorded the next Mechanical connections were all very solid, with most sequence of images, then advanced the filters and took components coupled by standard T-threads. The 100" all the sequences without further commands. In this tracked very well, keeping the star inside the ROI for way, multi-filter observations were made with no wast- many minutes. ed time; this will be important for possible future Before the Engineering Test, one of the greatest “production” speckle runs. unknowns was whether Drift Calibration would be Although the 100" theoretical resolution is less than practical for such a small FOV. Fortunately, this tech- 0.10", no added magnification was used, in order to nique was far easier and faster than expected, because maximize the FOV. Therefore, speckle observations of of accurate pointing of the 100" and using the largest double stars closer than about 0.20" were not estimated CMOS detector available. Full drifts of almost 10 sec- to be practical because of moderate under-sampling onds for Dec ~ 26o were achieved routinely. The ROI (about 5 pixels across the Airy disk). However, new allowed small file size, short write time and fast frame larger “full-frame” cameras should make higher- rate; more frames were recorded during each drift, to resolution speckle observations - all the way to the dif- yield higher quality linear regression for each drift. fraction limit - possible in the future, by providing a An intercom “count-down” procedure was devel- larger FOV with similar pixel size. The ideal pixel oped to coordinate timing between the T.O. (stopping sampling is about 7-8 pixels across the Airy disk, so a the RA drive) and Camera Operator (start recording). 1.5x Barlow would work well for 3.8μ pixels. With a little practice, it was easy to coordinate the star During this 4-hour Engineering Test run, only two position, telescope RA stop/re-start, data recording, and double stars were observed, because time was spent star recovery. The telescope declination remained sol- exploring the issues discussed above. A future id, with no shifting north or south that might have “production” run could observe a much higher number “lost” the star after drifting out of the FOV. Pure RA of stars following similar routine procedures. slow motion westward always returned the star to the

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 161

A New Opportunity for Speckle Interferometry on the Mount Wilson 100-inch Telescope

Conclusions All the major goals of the Engineering Run were achieved. These included: • Focus of the Speckle optical assembly was easily reached, with plenty of further adjustment capability remaining. • Drift Calibration was successfully demonstrated with the “wide” FOV (~2') of the large format CMOS camera. Recovery of the star and repeated drifts were quick and easy to do. • Speckle observations of two close double stars were successfully completed, including a reference star for the closer double. • Efficient multi-filter observations were made, with virtually no wasted time between filters, using FireCapture automatic filter control through ASCOM protocols. • Magnification of the f/11.5 modified Cassegrain focus was adequate to resolve double stars closer than 0.2". Slightly greater magnification (1.5x) should be practical for better Airy disk sampling, to approach the theoretical resolution of the 100" telescope. • Hardware, interfaces, communication and procedures were prepared and ready for the Student observations. • The telescope and amateur hardware were successfully used by the Student Team to make speckle observations. • During their field trip, the students contributed their own new speckle measurements to science, Figure 18. The PRHS students pose in the “Monastery” Library while immersed in the living history of Mount of Mount Wilson Observatory, just as some of the giants of 20th Wilson Observatory, Figure 18. century astronomy had posed with Albert Einstein more than 88 years earlier, during his visit in January 1931. Acknowledgements The authors are grateful to the Field Studies Collab- orative at Paso Robles High School for purchasing time on the 100" Telescope, and to Jon-Paul Ewing, PRHS Double Star Catalog, and the 6th Orbit Catalog, main- Science Department Head, for organizing and leading tained at the U.S. Naval Observatory. the Astrometry Field Research Team, and inviting the References authors to participate in helping develop a new Speckle capability for the students. Anderson, J.A., 1920, “Application of Michelson’s In- The authors also thank the Mount Wilson Institute, terferometer Method to the Measurement of Close and Executive Director Thomas Meneghini, for his time Double Stars.” Contributions from Mount Wilson and kindness in opening the 100" Telescope for the En- Observatory, No. 185, ApJ, 51, 263-275. gineering Test Run. Denny, R., 2019, https://ascom-standards.org Essential in making student speckle interferometry a successful reality were the participation, mentoring, Edelmann, Torsten, 2017. FireCapture2.6. http:// fire- guidance and inspiration of educators from the Institute capture.wonderplanets.de for Student Astronomical Research (InSTAR) and Gates, E., Garrett, B., Corgiat, P., Ezzell, M., Ewing, J- Boyce Research Initiatives and Education Foundation P., Harshaw, R., 2020a, “Astrometry of WDS (BRIEF). 13472-6235”, JDSO, 16 (2), 148-150 (this issue). This research has made use of the Washington

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 162

A New Opportunity for Speckle Interferometry on the Mount Wilson 100-inch Telescope

Gates, E., Hughes, A., McNerny, M., Rendon, R., Gar- McAlister, H.A., 1977, “Speckle Interferometric Meas- rett, B., Chung, S., Corgiat, P., Ezzell, M., Ewing, urements for Binary Stars - I”, The Astrophysical J-P., 2020b, “Close Binary Speckle Interferometry Journal, 215, 159. on the 100-inch Hooker Telescope at Mount Wil- McAlister, H. A., et al, 2005, “First Results from the son Observatory”, JDSO, 16 (2), 163-168 (this is- CHARA Array - I. An Interferometric and Spectro- sue). scopic Study of the Fast Rotator α Leonis Genet, R., Rowe, D., Meneghini, T., Buchheim, R., Es- (Regulus)”, ApJ, 628, 439. trada, R., Estrada, C., Boyce, P., Boyce, G., Ridge- Merrill, P. W., 1921, “Interferometer Observations of ly, J., Smidth, N., Harshaw, R., and Kenney, J., Double Stars”, PASP, 33, 209. 2016, “Mount Wilson 100-inch Speckle Interferom- etry Engineering Checkout.” JDSO, 12, 263-269, Michelson, A.A., & Pease, F.G., 1921, “Measurement March 2016. of the Diameter of α Orionis with the Interferome- ter”, ApJ, 53, 249. Harshaw, Richard and Rowe, David and Genet, Russell, 2017, “The Speckle Toolbox: A Powerful Data Re- Mount Wilson Institute, 2019, https://www.mtwilson.edu duction Tool for CCD Astrometry.” JDSO, 13, 52- 67, January 1, 2017. Rowe, David A. and Genet, Russell M., 2015, “User’s Guide to PS3 Speckle Interferometry Reduction Hartkopf, W.I., McAlister, H.A., Mason, B.D., Program”, JDSO, 11, 266-276. tenBrummelaar, T.A., Roberts, J.C. Jr., Turner, N.H., & Wilson, J.W., 1997, “ICCD Speckle Ob- Rowe, D., 2017, “WDS1.2 Search Program.” Private servations of Binary Stars - XVII. Measurements communication. During 1993-1995 From the Mount Wilson 2.5-M Rowe, D., Genet, R., 2020. “STB1.13 Bispectrum Pro- Telescope.” AJ, 114, 1639. cessing,” in preparation for submittal to JDSO. Hughes, A., McNerney, M., Chung, S., Rendon, R., Ewing, J-P., Harshaw, R., 2020, “Astrometry of WDS 09000-4933”, JDSO, 16 (2), 169-172 (this issue)

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 163

Close Binary Speckle Interferometry on the 100-inch Hooker Telescope at Mount Wilson Observatory

Emily Gates, Audrey Hughes, Mairin McNerney, Raul Rendon, Brighton Garrett, Sara Chung, Phoebe Corgiat, Marissa Ezzell, Jon-Paul Ewing

Paso Robles High School, California, USA

Abstract: This research team conducted astrometric measurements of the close binary stars COU 1757 and HU 1268. Using Speckle Interferometry on the historic Mount Wilson 100- inch telescope, the calculated position angle for COU 1757 was found to be 111.65°, with a separation of 0.169 arc seconds. For HU 1268, the position angle was calculated to be 338.45° and the separation was found to be 0.376 arc seconds. Drift calibrations and Bispectrum Anal- ysis were used to extract position angle and separations from the data for a complete analysis. Through the analysis of these double stars, subsequent data points were added to the cumula- tive historic observations of these star systems.

Introduction A team comprised of eight students from Paso Ro- bles High School (PRHS) conducted research at the Mount Wilson Observatory on the 100-inch telescope with the support of a small group of amateur astronomers. The team of researchers were able to congregate and establish observations through the PRHS Field Studies Collaborative: Astrometry Research Seminar to observe double stars using speckle interferometry. The purpose of this seminar was to allow the students to experience scientific research while also giving them an introduction into the field of astronomy and teaching them about the history of Mount Wilson. On June 11, 2019 (JD 2458646), two stars were Figure 1: Students inside the 100” dome selecting reference observed: COU 1757 and HU 1268. These stars were stars on the observation night chosen based on certain parameters: the resolution of the 100", the limited observations conducted on both tral class G5, with the magnitude of the primary star stars, and the conditions of the viewing night. For each being 9.6 and the secondary star’s magnitude being star observed, a reference star was chosen to accurately 9.97. The separation of the system is 0.18" and the po- process the speckle images. The reference stars were sition angle is 120°, based on the Grade 3 WDS orbit chosen based on how similar in magnitude and spectral with a period of 50 years. The reference star chosen class they were to the observed star, as well as their was SAO 45083, also in the spectral class G5. SAO proximity to the target. 45083 has a magnitude of 8.71 and its distance in rela- WDS 14260+4213 (COU 1757) was discovered in tion to the target star is 0.9°. 1978 and has a total of 23 observations; COU 1757 was WDS 14295+3612 (HU 1268) is in the spectral most recently observed in 2012. The star is in the spec- class F5. It was first discovered in 1905 and was most

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 164

Close Binary Speckle Interferometry on the 100-inch Hooker Telescope at Mount Wilson Observatory

Figure 3: View of the night sky through the 100” dome as Figure 2: The speckle optical assembly used for the observa- seen on the night of the observations, showing thin cirrus tions; for more details access the paper written by the team clouds. who tested the set up a week prior (Wasson et al. 2020)

recently observed in 2009. HU 1268 has a total of 18 was the only night reserved for the group on the 100- observations. The magnitude of the primary star is 9.77 inch telescope, they attempted speckle observations and the magnitude of the secondary star is 9.9. This star anyway, and could easily see the stars in the camera has a separation of 0.33 arc seconds and a position an- field through the clouds. gle of 332°. SAO 64192 was chosen for the reference star, with a magnitude of 9.1 and a spectral class G1Ⅲ. Drift Calibration Analysis The distance of SAO 64192 in relation to the target star The image collection was done using the 100” tele- is 0.3°. scope on Mt. Wilson, with a narrow region of interest strip (rather than full-frame images) to get a faster im- Equipment and Procedures age rate and more images. With a faster image rate and The images used to gather data in this study were more images, the data points for the drift calibration are collected on the 100-inch Hooker telescope at the more precise and accurate. With the drift calibration, Mount Wilson Observatory in California. At this loca- astrometric measurements of the observations were tion, the team acquired 1,000 images in each of the fol- properly corrected for camera misalignment and image lowing filters: Johnson B, Johnson V (Visual), SLOAN scale. i (near infrared), and Baader R (CCD LRGB series). During the drift calibration process, the team con- The exposures and gains of each of the images were ducted 10 drifts in order to calibrate the camera position continuously adjusted to optimize the filter being used angle and pixel scale of the images. The average of all through the data acquisition program FireCapture the angles is 2.181° with a standard deviation of 0.098, (Edelmann, 2019). The camera, loaned by Dave Rowe, and a pixel scale of 0.02659 arc-sec/pixel with a stand- had a large CMOS sensor to get a large field of view: ard deviation of 0.00005. The very consistent drift re- approximately 2 arc-minutes wide. This equipment was sults are shown in Figures 4 and 5. necessary to ease the process of finding each star and for the Drift Calibration. To find reference stars, Dave Speckle Autocorrelation Analysis Rowe’s search tool WDS1.0 (Rowe, 2017) was used. In Speckle Tool Box 1.05 (STB 1.05) (Harshaw, order to do this, the target stars were input into the tool, Rowe, and Genet, 2017) was used for speckle pro- which then found nearby, available reference stars from cessing to get the Autocorrelation of each double star the SAO catalogue. The team then selected the best ref- observed. First, the program was used to make a FITS erence star for each target star using the spectral classi- cube from all 1000 images captured. A FITS cube was fication and the magnitude. made for each of the four filters for both the observed The student team used the same speckle optical double star and reference star images. Each image was setup, shown in Figure 2, and followed protocols tested cropped to 128x128 pixels around the star before sav- one week earlier on the 100-inch telescope (Wasson et ing them as a FITS cube. The cubes were then pro- al, 2020). Unfortunately, high, thin cirrus clouds cov- cessed (average of the Fourier Transform of each im- ered the sky all evening (Figure 3). However, since this age) to produce Power Spectral Density (PSD) files. Once each cube had been processed, the Speckle Re-

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 165

Close Binary Speckle Interferometry on the 100-inch Hooker Telescope at Mount Wilson Observatory

Figure 4: Drift Calibration results for pixel scale. Figure 5: Drift Calibration results for camera angle on the sky.

duction tool found in STB 1.05 used the PSD files to shown in Figure 6. They are very clear, even though the display the Autocorrelation of the double star for each 1000 original speckle images were taken through high, filter. These Autocorrelations were then measured using thin clouds. the program, and the data collected was transferred to an Excel file. This process was done for both COU Results 1757 and HU 1268. The observations that lead to the analysis of the images occurred on June 11, 2019, 2019.444 (JD Bispectrum Analysis 2458646), and the analysis of the images occurred on Along with the FITS cubes created in STB 1.05, June 12, 2019 in the Mt. Wilson Library. The measure- Speckle Tool Box 1.13 (STB 1.13) (Rowe and Genet, ments for both stars were taken using Speckle Interfer- 2020) was used for the Bispectrum Analysis (BSA) of ometry. For COU 1757, the position angle was deter- the images. The FITS cubes for both the double star and mined to be 111.65° and the separation was found to be reference star had to be reprocessed so that they were 0.169 arc seconds; the data for COU 1757 is shown in BSA files. After they were all processed, these files Table 1. The position angle and separation for HU 1268 were run through the Bispectrum Phase Reconstruction are 338.45° and 0.376 arc seconds, respectively; these tool in STB 1.13 to produce images of the double star. values are found in Table 2. These images were then measured in the Bispectrum Due to the unusual optical train (shown in Figure 7) Phase Reconstruction tool and the data found were used to make the eyepiece accessible for public view- saved in the same excel file as the data collected in the ing, five reflections reversed East and West in the cam- Autocorrelation process. Again, this process was done era view from the normal sky view. Since this same set- for both COU 1757 and HU 1268. Examples of the up was used for the camera, this caused an East-West BSA reconstructed images in the Johnson V filter are reversal in the images collected. Therefore, we correct-

Figure 6: Bispectrum Analysis (BSA) Re-constructed images (V filter) of HU 1268 (left) and COU 1757 (Right). These images are oriented north-up and east-left, as on the sky, and are 64x64 Figure 7: The relay optics on Mt. Wilson’s 100” hooker telescope pixels (1.70x1.70 arc-sec) in size. that brings the focus to the public viewing platform

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 166

Close Binary Speckle Interferometry on the 100-inch Hooker Telescope at Mount Wilson Observatory

Autocorrelation (AC) Bispectrum Analysis (BSA) Position Angle Separation Position Angle Separation Filter (deg) (as) (deg) (as) Johnson B 108.70 0.167 113.67 0.180 Johnson V (Visual) 110.74 0.166 114.40 0.167 SLOAN i (Near infrared) 110.60 0.166 114.46 0.169 Baader R (CCD LRGB series) 110.73 0.166 109.88 0.165 Mean 110.19 0.166 113.10 0.170 Standard Deviation 1.00 0.000 2.18 0.007 Standard Error of Mean 0.50 0.000 1.09 0.003

Averages of all Filters for AC Position Angle Separation and BSA (deg) (as) Mean 111.65 0.169 Standard Deviation 2.21 0.005 Standard of Error of Mean 0.78 0.002

Table 1: Separation and Position Angle for COU 1757 using Autocorrelation and Bispectrum Analysis. Measurements made on JD2458646

Autocorrelation (AC) Bispectrum Analysis (BSA) Position Angle Separation Position Angle Separation Filter (deg) (AS) (deg) (AS) Johnson B 338.53 0.373 335.34 0.367 Johnson V (Visual) 338.62 0.374 340.28 0.391 SLOAN i (Near infrared) 338.89 0.375 338.54 0.370 Baader R (CCD LRGB series) 339.03 0.377 338.40 0.377 Mean 338.77 0.375 338.14 0.376 Standard Deviation 0.23 0.002 2.05 0.011 Standard of Error of Mean 0.12 0.001 1.03 0.005

Averages of all Filters for AC Position Angle Separation and BSA (deg) (AS) Mean 338.45 0.376 Standard Deviation 1.39 0.007 Standard of Error of Mean 0.49 0.003

Table 2: Separation and Position Angle for HU 1268 using Autocorrelation and Bispectrum Analysis Measurements made on JD2458646

ed the East-West reversal using the equation PA = 360 - Discussion PA (from STB). The purpose of the speckle observations was to add Figures 8 and 9 represent the calculated WDS orbit data and further the knowledge of the existing orbits of of each star with this team’s new data added to it. The these doubles. Both of the doubles, COU 1757 and HU average of the team’s data is represented by the red cir- 1268, are physical binary star systems. As seen in Fig- cles. ure 8 above, the data acquired during this seminar fol-

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 167

Close Binary Speckle Interferometry on the 100-inch Hooker Telescope at Mount Wilson Observatory

Figure 9: HU 1268 Plotted Orbit, with the new observation indicated by the red circle. Figure 8: COU 1757 Plotted Orbit, with the new observation indicated by the red circle.

lows the calculated orbit of COU 1757. However, our produce successful astrometry and images of each star point appears before where the point was predicted to chosen. be (measured 0.169" at 111.65o, predicted 0.18" at Throughout the seminar, the team had very few 120o). This could mean that the orbital period of COU difficulties. The biggest problem was the cloud cover 1757 is shorter than what was previously calculated. mentioned earlier in this paper. Another issue that came Based on our observations shown in Figure 9, the up was the students’ lack of experience in the field of orbit for HU 1268 may need to be recalculated, as our astronomy; this made it difficult to get everyone on the data point and those prior to it appear to drift away same page during both the observation and analysis from the current orbital path. portions of the seminar, causing the whole operation to While going through the drift calibration process take longer than expected. In order to avoid this confu- and collecting the images, the biggest issue that came sion in the future, further preparation may be necessary. up was the consistent thin cirrus cloud cover. The Despite these issues, the team was still able to work cloudy weather caused the images to be of a poorer together to collect quality data; the drift calibration, quality than desired, especially in the case of the imag- autocorrelation, and bispectrum analysis were all suc- es taken with the Johnson B filter. Fortunately, the im- cessful. Along with the success of the observational ages were still usable and we were able to acquire data part of this seminar, every student involved was able to from them. contribute in some way to the scientific research held at Mount Wilson, allowing each of them to engage in the Conclusion learning experience. With this in mind, this Field Stud- The objective of this research was to make speckle ies Collaborative was an overall success. observations of the close binary stars COU 1757 and HU 1268 to add to the double star research database. Acknowledgements By taking a thousand images at different exposures, We would like to thank Rick Wasson and Rachel gains, and filters (Johnson B, Johnson V (Visual), Freed for taking the time to read and revise our paper. SLOAN I (near-Infrared), Baader R (CCD LRGB se- We would also like to recognize and appreciate Tom ries) and using Speckle ToolBox 1.05 and Speckle Meneghini, Mt. Wilson Executive Director, for the op- ToolBox 1.13, the students gathered enough data to portunity to gather data using the 100-inch telescope at

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 168

Close Binary Speckle Interferometry on the 100-inch Hooker Telescope at Mount Wilson Observatory

Mt. Wilson, and his help with the collection of the data. Special thanks to the research team who set up the camera, offered expertise, and coached the students via Zoom meetings and paper writing. This research has made use of the Washington Double Star Catalog and the 6th Orbit Catalog maintained at the U.S. Naval Observatory. References: Edelmann, T., 2019. “Planetary Image Capture.” Fire- Capture, www.firecapture.de/. Harshaw, R., Rowe, D., and Genet, R., 2017, “The Speckle Toolbox: A Powerful Data Reduction Tool for CCD Astrometry”, JDSO, 13 (1), 52-67. Rowe, D., Genet, R., 2020. “STB1.13 Bispectrum Pro- cessing,” in preparation for submittal to JDSO. Rowe, David A., 2017. Private communication. Wasson, R., Estrada, R., Estrada, C., Harshaw, R., Ray, J., Rowe, D. Genet, R., Freed, R., Boyce, P., and Meheghini, T., 2020, “A New Opportunity for Speckle Interferometry on the Mt. Wilson 100-inch Telescope,” JDSO, 16 (2), 151-162 (this issue).

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 169

Astrometry of WDS 09000-4933

Audrey Hughes1, Mairin McNerney1, Sarah Chung1, Raul Rendon1, Jon-Paul Ewing1, Richard Harshaw2

1. Paso Robles High School 2. Institute for Student Astronomical Research (InStAR)

Abstract: This research team conducted an astrometric measurement of the double star WDS 09000-4933 (HD 77321), with a Julian observation date of 2458591 (April 17, 2019). The observed separation was 9.056 arc seconds and the position angle was 307.530 degrees.

Introduction A research group of students from Paso Robles High School in the Astrometry Field Research Program (Figure 1) collaborated with the Institute for Student Astronomical Research (InStAR) to measure the separation and position angle of a double star. This team of four students specifically investigated double star WDS 09000-4933 (Figure 2). By observing, recording, and analyzing this double star, a contribution was made to the data collected in previous years in hopes of gaining a further understanding of the nature of binary stars. In order to do this, the observation of this double star system included documenting the measurements of the position angle in degrees, and the separation in arcsec- Figure 1: Image of Team Mizar with the 60" telescope at onds. This double star was chosen based on limitations Mount Wilson Observatory, CA of the ground based telescope, which can resolve stars down to about 5 arcseconds separation. Using Las Cumbres Observatory which has 0.4-meter telescopes in the northern and southern hemispheres allowed for selecting a star in the southern hemisphere. The first published research of WDS 0900-4933 was in 1868 by J.M Gilliss (Gil 1868), with the last publication being in 2015. Gilliss initially discovered the double in 1852. Experiments and Procedures Using Dave Rowe’s Gaia WDS Catalog to select a system within the accessible parameters (> 0.5 arcsecond separation, delta magnitude < 3) , research on double star 09000-4933 could commence. The Las Cum- bres Observatory (LCO) granted telescope time, and 30 Figure 2: Image of WDS 0900-4933 (HD 77321) in As- images were requested, 10 each at exposure times of troImageJ Software

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 170

Astrometry of WDS 09000-4933

0.5, 1, and 2 seconds. The images were taken on a 0.4- Discussion m telescope located in Cerro Tololo in northern Chile. The images analyzed by our student team show a Along with these images, historical data was received separation of 9.056 arcseconds and a position angle of on the star from Dr. Brian Mason with the US Naval 307.530 degrees. Our measurements align well with the Observatory. past observations (Table 3) of this double star as seen The 30 images were analyzed using AstroImageJ plotted in Figure 3. When using Richard Harshaw’s (Collins. et al 2017) to measure each stars’ right ascen- Plotting Tool, which compiles data from the US Naval sion (RA) and declination (DEC). Within the program, Observatory and the Gaia DR2 data file, we noticed apertures of 4, 5, 6, and 7 were initially used to centroid that the parallax for the two stars are different but very the stars and determine precise RA and DEC values. close (Table 2). 1.23 milli-arcseconds and 1.14 milli- After the collection of the data, it was determined that arcseconds are smaller than 5.00 and are at the limits of an aperture of 6 was best to eliminate variables and at- what the Gaia instrumentation can measure. The prima- tain cleaner data. The average position angle and sepa- ry star has a distance of 813 parsecs and the secondary ration were then calculated using the observed RA and is at 877 parsecs. This puts a distance of about 64 par- DEC from the AstroImageJ software. secs between the two stars (over 200 light years), too Results far for them to be gravitationally bound. If we put the error (+ 0.02- 0.03 mas) into consideration the actual Using AstroImageJ, the average position angle was locations could be closer, the primary could be 1.198 calculated to be 307.530 and the average separation was mas and the secondary could be 1.173 mas. This sepa- 9.056 arc seconds. The data, including the averages of ration is only 0.025 mas and is the minimum possible separation and position angle, are displayed in Table 1. separation. The graph displayed in Figure 3 shows the data in rela- When plotting our data point alongside the historic tion to previous observations of the double star system. measurements (Table 3), we noticed that the 1st meas- This graph was created using Richard Harshaw’s Plot- urement taken in 1852 showed a significant difference ting Tool 3.10 (Harshaw personal communication).

Exposure

Time 0.5 1.0 2.0 (s) Position Position Image Separation Separation Separation Angle Angle Number (arcsec) (arcsec) (arcsec) (deg) (deg) 1 9.065 307.630 9.105 307.975 9.130 307.782 2 9.104 307.469 8.963 307.961 9.031 308.023 3 9.084 307.606 9.102 307.573 9.077 307.714 4 8.942 307.149 9.079 308.188 9.093 307.689 5 9.044 306.982 9.040 307.434 9.075 307.813 6 8.986 307.126 9.027 307.896 8.877 305.953 7 9.059 307.203 9.072 308.185 9.166 306.691 8 9.058 307.558 9.018 307.261 - - 9 9.119 307.394 9.075 307.995 - -

Mean Value 9.051 307.346 9.054 307.830 9.064 307.381 Standard 0.056 0.238 0.046 0.330 0.093 0.761 Deviation Standard 0.019 0.079 0.015 0.110 0.035 0.288 Error Separation (arcsec) Position Angle (DEG)

Total Mean Value 9.056 307.530

Mean Standard Deviation 0.0628 0.503

Mean Standard Error 0.0126 0.101

Table 1: Separation and Position Angle for 25 Images at Different Exposure Times on JD 2458591 (April 17, 2019)

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 171

Astrometry of WDS 09000-4933

A Star Px, G2 B Star Px, G2 Wtd Distance Parallax 1.23 1.14 OVERLAP -28 PXerr 0.02 0.03 RANGE 101 Err % 20% 3% % O-LAP -28% MIN DIST 800 855

MEAN 813 877 WTD PX 1.18

MAX DIST 826 901 WTD DIST 847

AB SEP 250,260 270,018 WTD SEP 260,733 Rad Vel 0.00 71.72 Radius 71.72 0.00 NO OVERLAP Lumin 1,704.74 0.00

Table 2: Distance (Parallax) Analysis (Plotting Tool 3.15)

from the rest of the points. Theta is 297.0 in 1852 and and confirmed. Our results are consistent with previous in less than 50 years it was measured to be 305.1. We observations of the star system, and have added to the suspect that the first measurement to be inaccurate due growing database of double star observations. to limitations of the transit circle telescope used. We removed that data point from our graph (Figure 3). Acknowledgements: We would like to thank Rick Wasson for taking the Conclusion time to read and revise our paper, the Las Cumbres Ob- The research group of students associated with servatory for providing prompt and quality images of Paso Robles High School made significant strides for- our star, and Karen Collins for developing the program ward in the research and analysis of double star WDS AstroImageJ for public use. We would also like to 09000-4933. By collaborating with InStAR (Institute thank Dr. Brian Mason of the US Naval Observatory for Students Astronomical Research), they gathered for supplying us with historical data on our star, and further data on the double star system WDS 09000- Richard Harshaw for creating his Gaia 2 plotting tool to 4933. As measurements of the position angle and sepa- aid us in graphing our star’s data. Further acknowledge- ration of the two stars were made, accuracy was judged ments go to Dave Rowe for providing a narrowed list of

Adjustments History

Year Theta Rho X Y Xp New Theta Made By Type

1900.30 305.1 8.93 -7.30625 5.13480 -0.00191 305.09809 I__1905 Ma 1902.29 303.4 9.07 -7.57224 4.99286 -0.00192 303.39808 WFC1998 Pa 1903.12 310.1 9.33 -7.13692 6.00967 -0.00192 310.09808 WFC1998 Pa 1934.20 307.6 9.12 -7.22588 5.56452 -0.00200 307.59800 B__1935 Ma 1964.10 306.7 9.40 -7.53690 5.61768 -0.00208 306.69792 WFC1983 Pa 1987.191 307.0 9.23 -7.37161 5.55475 -0.00215 306.99785 Tob2005 Pu 1987.191 308.0 9.10 -7.17111 5.60252 -0.00215 307.99785 Bvd2003 Pa 1991.45 307.8 9.15 -7.23013 5.60810 -0.00216 307.79784 TYC2002 Ht 1998.987 306.4 9.09 -7.31669 5.39418 -0.00218 306.39782 UC_2013 Eu 2000.26 307.2 8.99 -7.16101 5.43535 -0.00218 307.19782 TMA2003 E2 2015.000 307.822 9.15 -7.22798 5.61088 -0.00222 307.81978 Kpp2018 Hg 2019.29 307.53 9.056 -7.18194 5.51670 -0.00223 307.52777 PRHS C

Table 3: Past Measurement Data

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 172

Astrometry of WDS 09000-4933

WDS Stars to select from and Rachel Freed for providing support and knowledge throughout our research of double star system 09000-4933. References Collins, K., Kielkopf, J., Stassun, K, and Hessman, F., 2017, “AstroImageJ: Image processing and photometric extraction for ultra-precise astronomical light curves”, The Astronomical Journal, 153, No. 2 Gilliss, J.M. Washington Obs., Appendix 1, 63, 1868 Harshaw, Richard JDSO. Plotting Tool 3.15 (in publication)

Figure 3. Our data (red triangle) compared with all historical data (green diamonds). X and Y Coordinates are in arc seconds. Downward arrow shows linear trend line of position.

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 173

Observation and Investigation of 14 Wide Common Proper Motion Doubles in the Washington Double Star Catalog

Ryan Caputo, Brandon Bonifacio, Sahana Datar, Sebastian Dehnadi, Lian E, Talia Green, Krithi Koodli, Elias Koubaa, Calla Marchetti, Sujay Nair, Greta Olson, Quinn Perian, Gurmehar Singh, Cindy Wang, Paige Yeung, Peyton Robertson, Elliott Chalcraft, Kalée Tock

Stanford Online High School, Stanford, California

Abstract: As a class-wide introduction to double star research, we investigated and measured 14 physical systems with separations between 6" and 20" from the Washington Double Star Catalog. Between 8 and 12 images of each system were reduced using AstroImageJ to extract position angles and separations that are current for 2020.0. The resulting measurements are reported here and are plotted along with each system’s historical data. Along with these plots, each system’s measurements in Gaia Data Release 2 were analyzed to assess the probability that the two stars in the system might have a gravitational relationship.

Introduction limits of the instrument’s sensitivity, and some of the Targets for this study were selected and imaged by systematic errors associated with Gaia DR2 instrumen- the course TA, Ryan Caputo. The targets have compo- tation are not fully understood (Luri et. al., 2018). nent stars of similar brightness (delta magnitude < 3) Instruments Used and separations of approximately 10". These criteria For 13 of the 14 systems, images were obtained ensure that the stars can be resolved easily and meas- using a 6-inch aperture classical Cassegrain telescope. ured unambiguously. Moreover, the targets all have The methodology is as described in Caputo 2019. similar parallax and proper motions (PMs). The simi- There were no filters used. The camera and telescope larity of the component PMs is assessed by taking the combination yields a pixel scale of approximately 0.4“ ratio of the magnitude of the proper motion difference per pixel, giving excellent sampling for seeing-limited vector to the magnitude of the longer proper motion measurements. Guiding was employed for longer expo- vector between the two component stars. This ratio is sures to improve tracking accuracy. The remaining called the rPM, and double star systems are considered system, STF1547AB, was imaged using the Las Cum- to have common proper motion if its value is smaller bres Observatory 0.4m robotic telescope. than 0.2 (Harshaw, 2016). According to this criterion, all of the systems in Table 1 have common proper mo- Measurements tion. Two of them also have orbital solutions in the The position angle and separation of each system Washington Double Star Catalog. was measured using AstroImageJ. The measurements As is evident from Table 1, STF1050AB and are shown in Table 2. STF1124AB have parallaxes below 5 milliarcseconds Current measurements in the context of previous (mas), which causes the fractional parallax uncertainty measurements for these systems to be relatively high. This leads to a Previous measurements for each system were re- large uncertainty in the distances of these systems, quested from the US Naval Observatory. These data where distance is calculated by inverting the parallax. are plotted along with the measurements above for each In general, parallax measurements below 5 mas must be system in Figure 1. Outlying data points more than 3 treated with caution, as such low values approach the (Text continues on page 175)

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 174

Observation and Investigation of 14 Wide Common Proper Motion Doubles ...

Parallax of Parallax of Proper Motion of Proper Motion of System Secondary rPM Primary (mas) Primary (mas/yr) Secondary (mas/yr) (mas) (-9.8 ± 0.10, (-9.6 ± 0.08, STF1188 11.6 ± 0.06 11.5 ± 0.05 0.162 12.7 ± 0.06) 10.2 ± 0.06) ( 20.4 ± 0.12, (22.0 ± 0.23, STF 427 6.4 ± 0.08 6.4 ± 0.2 0.074 -38.0 ± 0.08) -41.0 ± 0.1) (-65.5 ± 0.09, (-64.0 ± 0.09, STF 872AB 12.9 ± 0.05 12.9 ± 0.04 0.050 4.6 ± 0.07) 1.72 ± 0.07) ( 248.1 ± 0.08, (246.1 ± 0.08, STF 612AB 33.7 ± 0.05 33.8 ± 0.05 0.015 -202.0 ± 0.06) -197.6 ± 0.06) (-296.7 ± 0.07, (-270.4 ± 0.31, COU 91AB 56.0 ± 0.05 55.9 ± 0.20 0.060 -355.8 ± 0.04) -365.0 ± 0.16) (13.9 ± 0.08, (16.2 ± 0.09, STF1219 19.6 ± 0.05 19.7 ± 0.05 0.119 -19.1 ± 0.06) -21.3 ± 0.06) (-17.3 ± 0.08, (-18.2 ± 0.07, STF1246 12.0 ± 0.04 12.0 ± 0.03 0.072 -7.3 ± 0.05) -8.4 ± 0.05) (-51.04 ± 0.13, (-41.0 ± 0.12, STT 195AB 11.0 ± 0.09 11.1 ± 0.07 0.184 19.2 ± 0.08) 19.0 ± 0.08) ( 1.7 ± 0.08, (2.26 ± 0.09, STF1050AB 4.2 ± 0.05 4.2 ± 0.06 0.021 -27.4 ± 0.06) -27.5 ± 0.07) (-12.6 ± 0.14, (-11.9 ± 0.11, STF1124AB 2.9 ± 0.07 2.9 ± 0.05 0.056 -1.3 ± 0.10) -1.3 ± 0.07) STF 443AB ( 598.0 ± 0.08, ( 588.7 ± 0.01, 41.8 ± 0.04 41.4 ± 0.05 0.0147 (ORB) -1243.9 ± 0.06) -1262.0 ± 0.09) (-71.4 ± 0.10, (-71.8 ± 0.21, STF1308 8.0 ± 0.05 8.0 ± 0.12 0.023 3.1 ± 0.10) 4.8 ± 0.19) STF1547AB (-330.3 ± 0.43, (-315.6 ± 0.11, 42.3 ± 0.08 42.3 ± 0.06 0.045 (ORB) -190.1 ± 0.12) -181.3 ± 0.07) (-46.2 ± 0.02, (-46.9 ± 0.03, HJ 540 5.6 ± 0.03 5.8 ± 0.04 0.018 20.2 ± 0.03) 20.8 ± 0.05)

Note: Systems with (ORB) following the designation have an existing orbital solution in the Washington Double Star Catalog.

Table 1: Parallax and proper motion data for each system, including the proper motion ratio (rPM) calculated as the ratio of the PM difference vector magnitude to the magnitude of the longer of the component PM vectors. All of these systems have rPM lower than 0.2, indicating common proper motion.

Number of Position Standard Separation Standard System Date Images Angle (o) Error on PA (“) Error on Sep STF1188 2020.11 12 201.34 0.016 16.38 0.015 STF 427 2020.03 10 206.06 0.295 7.16 0.121 STF 872AB 2020.01 10 215.86 0.076 11.44 0.018 STF 612AB 2020.03 10 200.07 0.021 16.09 0.008 COU 91AB 2020.03 10 143.60 0.022 10.75 0.007 STF1219 2020.03 10 82.40 0.174 12.15 0.056 STF1246 2020.03 10 116.04 0.029 10.58 0.009 STT 195AB 2020.03 10 138.41 0.056 9.83 0.012 STF1050AB 2020.01 9 20.58 0.041 19.37 0.013 STF1124AB 2020.01 10 325.32 0.312 19.34 0.130 STF 443AB 2020.03 10 56.17 0.053 6.74 0.010 STF1308 2020.01 10 84.49 0.043 10.54 0.010 STF1547AB 2020.05 10 330.43 0.081 15.68 0.013 HJ 540 2020.01 9 211.40 0.022 8.90 0.007

Table 2. Measurements of 14 double stars made in January, 2020.

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 175

Observation and Investigation of 14 Wide Common Proper Motion Doubles ...

standard deviations from the mean were removed from cating relatively higher noise in the earlier measure- each plot, and historical data points were corrected for ments. In each case, the historical measurements are the precession of Earth’s axis since the time of each plotted as circles; the student’s measurement, by con- measurement. Note that the plots of Figure 1 are trast, is a green square with an x. The plots are labeled chronological, because each measurement is colored with the discoverer code of the system as well as the according to the date on which it was made. Specifical- name of the student who made the measurement. ly, darker points are more recent. A common trend is that the lighter-colored points are more scattered, indi- (Continued on page 178)

Figure 1: Measurements of each system in the context of historical data, with more recent measurements colored darker, and the measurement reported in this paper shown as a green square with an x through it. (figure continues on next page)

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 176

Observation and Investigation of 14 Wide Common Proper Motion Doubles ...

Figure 1 (continued). Measurements of each system in the context of historical data, with more recent measurements colored darker, and the measurement reported in this paper shown as a green square with an x through it. (figure continues on next page)

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 177

Observation and Investigation of 14 Wide Common Proper Motion Doubles ...

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 178

Observation and Investigation of 14 Wide Common Proper Motion Doubles ...

Figure 1 (conclusion). Measurements of each system in the context of historical data, with more recent measurements colored darker, and the measurement reported in this paper shown as a green square with an x through it.

Likelihood of a Gravitational Relationship clear progression in shading from one side of the plot to The similar parallax and common proper motion of the other. On the other hand, systems that do not show these systems indicate that the component stars of each consistent relative motion over time will show darker are likely to be related in some way. For example, they points interspersed with lighter points, indicating that might share a common origin. Studying the trajectories the stars’ relative motion is smaller than the inherent of stars that were born together can help astronomers uncertainty in the measurement. understand galactic structure on a larger scale. Even For three of the systems, there was sufficient evi- more importantly, some of the systems might be binary. dence of movement over time that it was appropriate to For most of these systems, a binary relationship fit the data to assess the nature of the trend. These between the components is not defendable on the basis three cases were STF1547AB, STF443AB, and of the historical data plots in Figure 1, because the scat- COU91AB. The first two of these have orbital solu- ter among the measurements is larger than the stars’ tions on file at the USNO, and these are shown in Fig- relative motion over the time span of the plot. Since ure 2. Note that STF1547AB’s orbit has a grade of 5 the data are colored chronologically in Figure 1, sys- while STF443AB’s orbit has a grade of 4, indicating tems that exhibit consistent relative motion show a that STF1547AB’s solution is considered the less cer-

Figure 2. Existing orbital solutions for STF 1547AB (Grade 5) and STF 443AB (Grade 4).

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 179

Observation and Investigation of 14 Wide Common Proper Motion Doubles ...

Figure 3: STF443AB weighted 2nd-order polynomial fits, showing a more realistic fit on the right when the axes of RA and Dec are switched. Both the linear and polynomial fits had R2 ~= 0.7.

tain of the two. For COU91AB, an additional word of stars. For each of the three systems, the orientation of caution is appropriate, because the light-colored early the 2nd-order fit was selected according to these crite- measurement at the far left of the historical data plot ria. Still, none of the cases showed curvature suffi- might be causing the trend to seem more pronounced ciently pronounced as to be definitive. than it actually is. Therefore, any inferences about this The chronological order of the points plotted on system must be understood as especially preliminary. Figures 3 and 4 is displayed via the colormap, where Historical measurements for STF443AB, lighter points correspond to measurements that were STF1547AB, and COU91AB were weighted according made earlier in time. The progression of the points to a system developed by Richard Harshaw (Harshaw, from light to dark across each plot indicates the chrono- 2020). The weighting criteria included measurement logical trend. type, telescope aperture, and number of nights. After weighting, linear and second-order polynomial fits were Escape Velocities performed. The purpose of these fits was to assess In situations such as these, where historical meas- whether the seeming curve in the motion of the second- urements span an insufficient time period for a plot of ary with respect to the primary was more likely than the past measurements to definitively characterize the sys- linear trend which would occur for unbound systems. tem as binary, one metric that can be employed is the Sometimes, the fitting software produces inappro- system’s escape velocity. In order to calculate this, two priate results when the historical measurements are numbers are needed: the mass of the primary star and close to perpendicular with respect to the axis of Right the spatial separation of the stars. Once these numbers Ascension. This is because the fitting routine is look- are obtained, the escape velocity can be calculated using for the best-fit parabola that has a unique y for eve- ing Equation 1 ry x, not the best-fit orbit. Figure 3 shows a case for 2GM which the 2nd-order polynomial fit of RA with respect vesc = [1] to Dec yields a more reasonable result than a fit of Dec r with respect to RA. This example illustrates the im- portance of selecting the vertical axis of the second- where M is the mass of the primary star and r is the sep- order fit to ensure that the fit makes sense in the context aration of the primary and secondary in space. of the data, and to maximize the R2 value of the fit. If the secondary star is moving faster than escape For instance, a curve that does not have a possibility of velocity relative to the primary star, then the likelihood enclosing the origin, where the primary star is located, that the system is binary decreases, and vice versa. would suggest no gravitational relationship between the However, one caution is that both the relative velocity

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 180

Observation and Investigation of 14 Wide Common Proper Motion Doubles ...

Figure 4. STF1547AB and COU91AB with weighted linear and 2nd-order polynomial fits. COU91AB’s fits had R2=0.616 (linear) and R2 = 0.697 (polynomial). STF1547AB’s fits had R2 0.819 (linear) and R2 = 0.831 (polynomial).

and the escape velocity are computed based on esti- stars was computed as the stars’ transverse separation mates that have large error bars. in radians divided by their parallax. The radial compo- To find the mass of the primary star, the star’s nent of the stars’ separation is not incorporated, because spectral type was determined from its temperature listed this value has an especially large associated error for in Gaia DR2. Its luminosity was also obtained from the systems in this study. For most of these systems, Gaia DR2 where available. For cases in which lumi- the error on radial separation is almost as large or even nosity was not listed in Gaia DR2,missing, it was calcu- larger than the radial separation itself. In other words, lated from the magnitude and parallax of the star ac- given the error on the corresponding parallax measure- cording to Equations 2 and 3. ments, the stars in these systems might be exactly the same distance from Earth. Therefore, incorporating M= m +5( log p + 1) [2] their separation in the radial dimension into r has the potential to artificially lower the computed system es- where M is the absolute magnitude, m is the apparent cape velocities. Because the separation of the stars was magnitude, and p is the parallax. only considered in two dimensions, the escape velocities computed here should be considered to be an upper L 0.4( 4.85−M ) bound on the system escape velocity. =10 [3] The velocity of the secondary star relative to the L primary incorporated the stars’ relative proper motions and their radial velocities, where available in Gaia where L is the luminosity of the star, L is a solar lumi- DR2. Since radial velocities are listed in units of km/ nosity, and 4.84 is the absolute magnitude of the Sun. sec in Gaia DR2, the proper motions were converted from milliarcseconds per year to km/sec according to The temperature and luminosity of the primary star Equation 4, were then used to locate it on a Hertzsprung-Russell mas 1 1 2 1 3.086 1013 km 1 yr (HR) diagram, where its position was used to verify    pc    7 [4] that it was on the Main Sequence. All of the stars in yr1000mas 3600 360  plx pc 3.54 10 s this study had temperatures and luminosities consistent with Main Sequence stars. The HR diagram position (where the values from Gaia are in red) before compu- was then used to estimate the mass of each primary. ting the magnitude of the secondary motion vector sub- The spatial separation r of the primary and secondary tracted from the primary.

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 181

Observation and Investigation of 14 Wide Common Proper Motion Doubles ...

Mass of Transverse Upper Bound Es- Relative 3D or 2D System Primary separation cape velocity space velocity (solar masses) in space (pc) (m/s) (m/s) STF1188 1.21 0.0068 1234 1060*

STF 427 2.23 0.0053 1904 2556*

STF 872AB 1.73 0.0043 1550 1210*

STF 612AB 0.85 0.0023 1781 685

COU 91AB 0.45 0.0009 2160 2353*

STF1219 0.82 0.0030 1561 826

STF 1246 1.19 0.0043 1541 921

STT 195AB 1.55 0.0043 1759 4559

STF1050AB 2.33 0.0218 952 550*

STF1124AB 2.23 0.0319 627 1021*

STF 443AB 0.71 0.0008 154** 2239

STF1308 1.67 0.0064 1505 1884

STF1547AB 1.10 0.0018 2312 2007

HJ 540 1.48 0.0077 1289 782*

* Denotes a 2-d relative velocity if radial velocities are not available in Gaia DR2. ** For this system, 3-d spatial separation was used instead of transverse separation in the escape velocity calculation because the error on distance was not as large as for other systems in the study.

Table 3: Estimates of mass, spatial separation, relative velocity, and escape velocity.

Unlike radial separations, radial velocities are the spirit of Brian Mason’s call for observations measured from Doppler shifts, and have a low associat- (Mason, 2020). The systems we studied and measured ed error, which justifies their inclusion in the relative are candidates for a physical relationship, making them motion calculation. Where radial velocities are not important systems to follow over time. Continued ob- available, the relative space velocity is two dimensional servation and measurement of these and other double and should be considered a lower bound. The systems star systems is essential to our understanding of stellar to which this applies are asterisked in Table 3. motions and stellar orbits, which indirectly yields clues Because they are estimated from so many impre- about galactic structure and stellar evolution. cisely-known values, most of the escape velocities Since its establishment in the late 1900’s, the Wash- shown in Table 3 are not sufficiently different from the ington Double Star Catalog has become continuously stars’ relative velocities to base a definitive conclusion more valuable as measurements are added, making or- on their relative values. The escape velocities and rela- bital solutions possible for increasingly long-period tive velocities would need to differ by a factor of ap- systems and characterizing the motions of increasingly proximately 4 or 5 to support or challenge a conclusion slow-moving stars (Tenn, 2013). The measurements in regarding whether the system was gravitationally this paper constitute our class’s contribution to that am- bound. Nevertheless, the numbers shown here can pro- bitious project. vide a rough estimate that might inform other pieces of evidence. Acknowledgments This research was made possible by the Washington Conclusion Double Star catalog maintained by the U.S. Naval Ob- Measurements of 14 double star systems with simi- servatory, the Stelledoppie catalog maintained by lar parallax and proper motions are contributed here in Gianluca Sordiglioni, Astrometry.net, AstroImageJ

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 182

Observation and Investigation of 14 Wide Common Proper Motion Doubles ...

software which was written by Karen Collins and John Harshaw, Richard, 2016, “CCD Measurements of 141 Kielkopf, and Stellarium software by Fabien Chéreau. Proper Motion Stars: The Autumn 2015 Observing This research also used data from the European Space Program at the Brilliant Sky Observatory, Part 3”, Agency’s Gaia Data Release 2 (https:// Journal of Double Star Observations, 12 (4), 394 - www.cosmos.esa.int/gaia), processed by the Gaia Data 399. Processing and Analysis Consortium (DPAC, https:// Harshaw, Richard, 2020. Private communication. www.cosmos.esa.int/web/gaia/dpac/consortium ). Funding for the DPAC has been provided by national Luri, X., A. G. A. Brown, L. M. Sarro, F. Arenou, C. A. institutions, in particular, those participating in the Gaia L. Bailer-Jones, A. Castro-Ginard, J. de Bruijne, T. Multilateral Agreement. Prusti, C. Babusiaux,, and H. E. Delgado. “Gaia Special thanks to Richard Harshaw for his advice Data Release 2: Using Gaia parallaxes”, Astronomy on our paper as well as developing and sharing the Plot and Astrophysics, 616, A9, 1 - 19. Tool 3.18 that facilitated graphing the historical observations and weighting the data for the fits. Thanks also Mason, Brian, 2020, “Catalog Access and New Lists of to Richard Harshaw and Rick Wasson for reviewing a Neglected Doubles”, Journal of Double Star Ob- draft of this paper and for making many valuable sug- servations, 16 (1), 3 - 4. gestions for improvement, which we have incorporated Tenn, Joseph, 2013. “Keepers of the Double Stars”, into this final version. Journal of Astronomical History and Heritage, 16 References (1), 81 - 93. Caputo, Ryan, 2019, “The Human Element: Why Ro- botic Telescope Networks Are Not Always Better, and Performing Backyard Research”, Journal of Double Star Observations, 15 (3), 408 - 415.

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 183

GAIA and CCD Observations Indicate that Herschel Double Star 10134-5054 HJ 4299 is not Gravitationally Bound

Karl Schmidt

The Branson School Ross, CA

Abstract: The goal of this research was to contribute to the 191 year old dataset of the double star WDS 10134-5054 (HJ 4299) using measurements made by GAIA and the LCO 0.4m robotic telescopes because the true nature of these two stars is yet undetermined. The LCO measurements show continued change in separation and position angle, however, the Gaia parallax measurements strongly suggest that the stars are not gravitationally bound and are in fact separated by over 300 parsecs. GAIA temperature and magnitude measurements predict that these stars are roughly within 10 Myr of each other in age. And GAIA proper motion measurements better explain the relative motion of the two stars than a gravitational bond. This paper demonstrates some of the analysis possible in the field of double star astronomy using GAIA data to address uncertainty in the nature of historical double stars that continue to have ambigu- ous relative motion.

Introduction than an optical binary, the separation between the stars The star named HJ 4299 (WDS 10134-5054) was and their position angle can be successively measured. first measured in 1834 by John Herschel and while it If an elliptical orbit fits the data well, then the likeli- has had roughly 12 observations in the last 191 years hood of the stars being gravitationally bound is very there remained a note on Stelle Doppie that “the nature high and information about the masses of the stars can of this double is uncertain”. This system includes an be determined. orange K4/5 star with a white A0 as the secondary It is also possible to rule out that the stars are gravi- (Houk 1978), with relative magnitudes of 7.4 and 8.6 tationally bound by determining the distances to the respectively (GAIA DR2). Over the last 191 years, the stars by measuring the stellar parallax. Stellar parallax separation has changed from 50.0" to 30.4" while the is a measure of how much the location of the star shifts position angle has changed from 328° to 320° (WDS). relative to the much more distant background stars from As part of the Astronomy Research Seminar, the objec- two maximally separated viewpoints in Earth’s orbit (6 tive was to contribute CCD measurements of the sepa- months apart). Also, proper motion can be analyzed to ration and position angle and look at possible orbital predict the probability of the stars being gravitationally calculations as no orbit calculation exits in the US Na- bound (Harshaw 2018). val research ORB6 database. A secondary goal was to Similar distances to the Earth is valuable support- see what could be learned from the GAIA DR2 meas- ing evidence in determining if the relative motion of urements. stars is due to mutual gravitation. Gravitationally bound When two stars appear very near each other in the stars are usually within 1000 AU from each other field of view it is possible that they are gravitationally (Harshaw 2018) and the occurrence rate of binaries de- bound and in orbit around the center of mass. It is also creases with the inverse of the separation out to around possible that the two stars only appear very close to- 3500 AU, this is known as Öpik’s law (Lépine & Bon- gether from our perspective, yet they are distant from giorno 2007 as referenced in Longhitano and Binggeli each other and not gravitationally bound. In order to 2009). The population of ultra wide binaries beyond determine if two stars are gravitationally bound rather 3500 AU separation decreases even more rapidly as the

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 184

GAIA and CCD Observations Indicate that Herschel Double Star 10134-5054 HJ 4299 ...

separation increases, and yet, there is evidence of bina- urements it is unclear if there had been parallax meas- ries out to 100,000 AU (Lépine & Bongiorno 2007). urements made for these stars and no distances were Examples of these ultra wide binaries and triple star given on Stelle Doppie as of October 2019. Queries to systems exist such as Kö 3 A-BC, where HD 221356 A GAIA DR2 through VizieR using any of the star names likely orbits HD 221356 BC at a distance of roughly and designations on Stelle Doppie did not yield any 11,900 AU (Caballero 2007), our nearest neighbor star measurements of these two stars. As you can see in fig- Proxima Centauri is in a hyperbolic “orbit” of α- ure 1 there are many other fainter stars in the field, Centauri AB (a double itself) at a distance of however, the bright stars were mysteriously not in the 15,000 AU (Matvienko and Orlov 2014), and a there is results list. a brown dwarf orbiting as a companion to TW Hya at Better luck was had with Aladin Software. Aladin 41,000 AU (Teixeira et al. 2008). Furthermore, there is is a software package that can access online databases evidence from computer simulations conducted by including plate solved images of the sky that can be Reipurth and Mikkola that triple star systems can give used to make measurements. After searching the name rise to stable, ultra-wide binaries up to 80,000 AU (~0.5 of the star produced no results, the J2000 coordinates pc) that are stable for 100 Myr (2012). Outside the were searched and the target stars were located, with range of 100,000 AU it is unlikely that a mutual gravi- the DSS2 image, shown in figure 3, superposed. Click- tational force plays a key role in the motion of the stars. ing on these two stars showed different star names, HD Harshaw describes a methodology for prescribing a 88812 (blue) and HD 88813 (red). Clicking on these probability of a binary system being physical rather star name links opens the star information page in the than optical based on 4 factors including a parallax fac- Simbad database, where there are the many identifiers tor and a proper motions comparison (2018). The paral- for these stars as well as links to VizieR database que- lax factor is a comparison of the distances from Earth, ries in various data sets, such as GAIA DR2 (See Ap- this factor ranges from 0.0 to 1.0 with greater values pendix for GAIA DR2 designations). indicating similar distances, see equation 1. The proper The Simbad star information pages list these stars motion factor compares the direction and magnitude of with several names: including 10134-5054A and 10134 the motion of each star relative to Earth on a scale from -5054B, while only HD 88812 (blue star) is labelled as 0.0 to 0.15 with identical proper motions resulting in a HJ 4299 B, a double star. (The designation HD stands value of 0.15, see Equation 2. According to Harshaw, for Henry Draper Catalog, a catalog of over 272,000 “two stars that are in orbit around one another should objects made between 1918 and 1924.) In Positions and have identical, or very nearly identical, proper mo- Proper Motions - South, Bastian et al. marked both HD tions.” The subject of this paper, HJ 4299, had not been 88812 (blue) and HD 88813 (red) as double stars analyzed by Harshaw 2018. (1993). However, later in 1996, Lasker et al. gave HD The CCD Images were to be taken with the Las 88812 (blue) a “False” marker for multiple objects in Cumbres Observatory (LCO) robotic telescope network the HST guide star catalog, while HD 88813 (red) does and measured in AstroimageJ, more on these methods not have an entry in this database, adding to the mys- below. Along with these measurements, measurements tery. of the stars position angle, seperation, parallax (distance), and proper motion presented in the GAIA Methods DR2 were analyzed, however tracking these down Observations were made with the Las Cumbres Ob- proved unexpectedly difficult. servatory (LCO) robotic telescopes. For these observations I used the 0.4m telescopes with a SBIG 6303 Accessing GAIA DR2 CCD camera. The telescopes are Schmidt-Cassegrain, GAIA is an ESA spacecraft attempting to map modified Meade telescopes and are mounted on equato- nearby stars in the Milky Way galaxy (ESA 2018). rial mounts and the SBIG cameras have a field of view GAIA is orbiting around the Sun with the Earth at L2, a of 29.2 x 19.5 arcminutes, with the plate scale being gravitational inflection point in the Earth-Sun system 0.571 arcseconds per pixel (LCO 2019). that allows the spacecraft to orbit the Sun with the Twenty images were captured at Siding Spring Ob- Earth on a 1 year timescale and only minor course cor- servatory in New South Wales, Australia (Lat: 31 16′ rections every 23 days (NASA/WMAP Science Team 23.88"S, Long: 149° 4′ 15.6"E, Elev: 1,116 m) (LCO 2019). This orbital position allows GAIA to view the 2019) on October 23, 2019, between UTM 17:47:11 entire celestial sphere and make repeated measurements and 18:06:54 with exposure times of 1.28 seconds. The through the year including measurements of parallax LCO network reduced and plate solved the images. In (stellar distance) and proper motion (direction of mo- AstroimageJ, the separation and position angle (from tion across the celestial sphere). Prior to GAIA’s meas- North to East) were measured from centroid to centroid

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 185

GAIA and CCD Observations Indicate that Herschel Double Star 10134-5054 HJ 4299 ...

Figure 1. AstroimageJ analysis example.

of each star as shown in Figure 1. These measurements 22 (PCPCpmra− pmra) +( pmdec − pmdec ) were repeated on each of the 20 images and then aver- Ppm =1 −  0.15 [2] 2 2 2 2 aged. The standard deviation and standard error of the PPCCpmra+ pmdec + pmra + pmdec mean (SEM) were calculated for each average. GAIA DR2 observations of the two stars’ right as- Findings censions and declinations made around 2015.5 were The position angle and separation measurements used to calculate the separation and position angle. The from LCO in 2019.8 and GAIA in 2015.5 (see Table 1) separation was calculated using a spherical geometry follow the historical trend of decreasing separation of equation presented by Michael Richmond (2005). And the stars, while they also exemplify that there is scatter the position angle was calculated using the position an- among the data and the decreasing trend is not con- gle equation presented in Buchheim 2008. sistent, see Figure 2A. The parallax factor and proper motion factor were The disparity between the parallax measurements calculated using the equations presented in Harshaw strongly suggests that these two stars make a visual pair 2018 by using the Excel spreadsheet linked in that pa- and not a gravitationally bound system. The parallax per. angles shown in Table 2 are very small, however, and, according to Harshaw, GAIA parallax measurements PC− below about 5 mas are unreliable or at least have much P =−1 dd [1] greater error bars than are presented in the GAIA DR2 px 1 (PC+ ) (personal communication, November 2019). The ESA 2 dd

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 186

GAIA and CCD Observations Indicate that Herschel Double Star 10134-5054 HJ 4299 ...

Separation Standard Dev. SEM PosAng Standard Dev. SEM

(arcsec) Sep. (as) (as) (deg) PA (deg) (deg)

LCO (2019.8) 30.47 0.11 0.024 327.48 0.19 0.043

GAIA DR2 (2015.5) 30.45 327.53

Table 1. Contemporary Separation and Position Angle Measurements

Figure 2: Historical measurements of companion star (Blue 88812) relative to the primary (Red 88813). (A) There is a drift in the position over the century, with some scatter. The red square represents the measurements made with the LCO images and the blue diamond represents the position measured by GAIA. (B) The Herschel measurement shown as the black triangle, made 65 years earlier than the next measurement, is twice as distant as the other measurements. It is hard to say if this is a significant movement or uncertainty in Hershel’s measurement.

reports the measurement error is at least below 0.1 mas (personal communication, November 2019). The ESA (2018). The difference between the parallax measure- reports the measurement error is at least below 0.1 mas ments of more than a factor of 2 means these stars are (2018). The difference between the parallax measure- not the same distance from Earth. The distance between ments of more than a factor of 2 means these stars are these two stars is 8.4 x 107 AU, a distance well beyond not the same distance from Earth. The distance between the commonly found values for physical binaries of these two stars is 8.4 x 107 AU, a distance well beyond within 1000 AU (Harshaw 2018), and beyond the wid- the commonly found values for physical binaries of est known binaries that may extend out to 105 AU within 1000 AU (Harshaw 2018), and beyond the wid- (Lépine & Bongiorno 2007). est known binaries that may extend out to 105 AU The disparity between the parallax measurements (Lépine & Bongiorno 2007). strongly suggests that these two stars make a visual pair The proper motion of these two stars explains why and not a gravitationally bound system. The parallax the separation is decreasing; both stars move roughly angles shown in Table 2 are very small, however, and, northwest, while the speed of HD 88813 (red), further according to Harshaw, GAIA parallax measurements to the southeast, is greater, see Figure 3. Combining the below about 5 mas are unreliable or at least have much proper motions and the parallax measurements, greater error bars than are presented in the GAIA DR2 Harshaw’s analysis predicts these stars are not a physi- Proper motion right Proper motion declination Parallax (mas) Distance (pc) ascension (mas/yr) (mas/yr) HD 88813 -17.201 +/- 0.067 12.647 +/- 0.077 1.3994 +/- 0.04 714.6 (red) HD 88812 -13.646 +/- 0.070 7.272 +/- 0.071 3.2733 +/- 0.04 305.5 (blue) Table 2: Proper motion and Parallax data from GAIA DR2

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 187

GAIA and CCD Observations Indicate that Herschel Double Star 10134-5054 HJ 4299 ...

Figure 3: Directions of proper motions. (L) The proper motion of each star is shown with the relative motion vector (shown in black) as the difference between the two motion vectors shows the direction of the motion of HD 88812 (blue) relative to HD 88813 (red).The relative motion vector agrees with the historical trend of the relative positions. This relative motion does not rule out an orbital motion, however this relative motion has continued throughout the last century and therefore suggest only a very long orbital trend and a large distance between the stars. (R) Image of the two stars, in the same orientation, the relative motion is such that the separation has decreased.

cal binary, see Table 3, primarily due to the very low Proper Motion Distance distance probability. Probability Binary Probability Physical? (scaled by Probability Using the GAIA DR2 parallax measured distances [1] (Table 2), the absolute magnitude can be approximated 0.15) [2] (Table 3) using the distance magnitude relationship shown in Equation 3. 0.1436 0.0977 0.2413 No The stars’ temperatures and absolute magnitudes were From Harshaw 2018 spreadsheet

d Table 3: Binary Probability Factors Absolute mag=− apparent mag 5log [3] 10

plotted on an HR Diagram, shown in Figure 4, allowing an approximation of the size and age of the stars to be made.

Apparent Mag Absolute Effective Distance Spectral Star (G band magnitude Temperature Notes: (pc) class (optical) [3] (K)

HD 88813 7.3785 714.6 -1.89 3984.03 K4/5 E Red giant

Just leaving main sequence HD 88812 8.5978 305.5 1.17 8806 A0V C to the giant branch

Data are from GAIA DR2, spectral class is from Houk 1978.

Table 3: Magnitude and Temperature data

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 188

GAIA and CCD Observations Indicate that Herschel Double Star 10134-5054 HJ 4299 ...

Figure 4: Spectral analysis. (A) HD 88813 is a red giant late in its lifespan. HD 88812 is a white star starting to branch from the main sequence to become a red giant. These spectral classes and luminosities suggest the stars have similar masses. (B) Evolu- tionary tracks of stars based on mass.

Based on the spectral classes shown in Figure 4, it Discussion can be determined that the stars have similar masses, GAIA parallax data strongly suggests that HD roughly 4 solar masses, based on the luminosities 88812 (white) is closer to the Sun than it is to HD (Fraknoi, Morrison, and Wolff 2017). Figure 4B shows 88813 (red). Though the relative proper motions agree that stars of this mass take between 2.2 x 108 yrs and 7 with the historical trend and do not rule out an orbital x 107 yrs to branch from the main sequence across the motion, and the parallax measurements suggest similar red giant branch (Fraknoi, Morrison, and Wolff 2017). ages to the stars, it is extremely unlikely that these stars If HD88812 has the lower mass of the two, it is possi- are gravitationally bound based on their distance to ble that it is within 7 x 107 years of the age of the red each other. I hope this paper offers some context to un- giant HD 88813. It is therefore possible that these stars derstanding more deeply Harshaw’s parallax and proper did from around the same time, from the same molecu- motion factors and that this paper exemplifies the im- lar cloud, and were once gravitationally bound, even if pact of the GAIA data to the field of double star astron- they have since drifted apart. However, with the system omy. mass constrained to between 7 and 10 solar masses from the HR diagram evolutionary tracks, a rough anal- Acknowledgements ysis of this system using Kepler’s Third Law, an ap- The following resources were used proximate system mass of 8 times the solar mass, and a • Washington Double Star Catalog semimajor axis of the difference in distances from • Aladin Sky Atlas v10.0 Earth (409 parsecs) approximates an orbital period of • Simbad: VizieR ~1011 years (Genet, et al. 2015). This orbital period is entirely unrealistic for two reasons: first these stars’ Thanks to Dr. Brian Mason for supplying the his- lifetimes are much shorter at ~109 years, and second, torical data for this system. binaries distant from each other can be pulled apart as Thanks to Rachel Freed for guidance and feedback they pass through the spiral arms of the Milky Way in and the Fall 2019 cohort of the Astronomy Research their orbit around the galactic center (Harshaw, person- Seminar for comradery and inspiration. al communication, November 2019), every ~108 years. Thanks to Dr. Richard Harshaw for review and

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 189

GAIA and CCD Observations Indicate that Herschel Double Star 10134-5054 HJ 4299 ...

feedback. Lépine, S. and Bongiorno, B., 2007, “New distant companions to known nearby stars. II. Faint compan- References ions of Hipparcos stars and the frequency of wide Buchheim, R., 2008, “CCD Double-Star Measurements binary systems”, The Astronomical Journal, 133, at Altimira Observatory in 2007”, Journal of Dou- 889 - 905. ble Star Observations, 4, 27-31. Matvienko, A.S. & Orlov, 2014, “Dynamic status of the Caballero, J. A., 2007, “Southern very low mass stars wide multiple system α Centauri + Proxima V.V.”, and brown dwarfs in wide binary and multiple sys- Astrophysical Bulletin, 69, 205. https:// tems”, The Astrophysical Journal, 667,.520. doi.org/10.1134/S1990341314020084 CSIRO. (n.d.) The Hertzsprung-Russell Diagram., Re- NASA/WMAP Science Team. (March 18, 2019). What trieved on December 10, 2019 from: https:// is a Lagrange Point? Retrieved from: https:// www.atnf.csiro.au/outreach/education/senior/ solarsystem.nasa.gov/resources/754/what-is-a- astrophysics/stellarevolution_hrintro.html. lagrange-point/ European Space Agency (ESA). (April 27, 2018). Reipurth, B. and Mikkola, S., 2012, “Formation of the GAIA Data Release 2 (GAIA DR2). Retrieved widest binary stars from dynamical unfolding of from https://www.cosmos.esa.int/web/gaia/dr2. triple systems”, Nature, 492, 221-4. doi:10.1038/ Fraknoi, A., Morrison, D., and Wolff, S. C., 2017, nature11662 “Evolution from the main sequence”, Astronomy. Richmond, M. (March 10, 2005). Precession, Proper OpenStax. Rice University. Pg. 772 Motion, and Angular Separation. Retrieved from: Genet, R. et al., 2015, “Speckle Interferometry of Short http://spiff.rit.edu/classes/phys301/lectures/ -Period Binary Stars”, Journal of Double Star Ob- precession/precession.html#sep servations, 11 (1S), 323. Teixeira, R., Ducourant, C., Chauvin, G., Krone- Harshaw, R., 2018, “Gaia DR2 and the Washington Martins, A., Song, I. and Zuckerman, B., 2008, Double Star Catalog: A Tale of Two Databases”, “SSSPM J1102-3431 brown dwarf characterization Journal of Double Star Observations. 14 (4), 734- from accurate proper motion and trigonometric par- 740. http://www.jdso.org/volume14/number4/ allax”, A&A, 489, 825-827, DOI: 10.1051/0004- Harshaw_734_740.pdf. 6361:200810133 Houk, N., 1978, “Catalogue of two dimensional spec- Washington Double Star Catalog (WDS) (n.d.). Naval tral types for the HD stars, Vol. 2.” Michigan Spec- Oceanography Portal (Retrieved in October tral Survey. Ann Arbor, Dep. Astron., Univ. Michi- 2019).https://www.usno.navy.mil/USNO/ gan. astrometry/optical-IR-prod/wds/WDS

Las Cumbres Observatory, 2019, “0.4-meter”, Re- trieved from: https://lco.global/observatory/ telescopes/0-4m/.

Appendix

HD 88812 (blue): Gaia DR2 5358556096510172288 HD 88813 (orange): Gaia DR2 5358556096510171520

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 190

Counter-Check of Binaries Reported to be Detected in Gaia DR2 as well as an Equal Mass “Twin” Binary Population

Wilfried R.A. Knapp

Vienna, Austria [email protected]

Abstract: A recent paper (El-Badry et al. 2019, in the following EB19) reports the discovery of a sharp excess of equal mass “twin” binaries based on the data from an earlier paper (El- Badry and Rix 2018, in the following EB18) reporting the construction of a very pure catalog of ~55,000 wide binaries based on Gaia DR2 catalog data. This report counter-checks both propositions using basically the identical Gaia DR2 catalog data, but with different assessment methods and different quality requirements especially regarding the relative parallax data error and using Gaia DR2 StarHorse catalog data for star masses with the result that both papers seem somewhat questionable in their use of existing data and also in their conclusions. This report contradicts the EB18 “very pure” claim with the assessment that >50% of the reported binary pairs are, with more stringent data selection and evaluation criteria, most likely optical pairs and not binaries. The culprit for this disappointing record is the allowance for Gaia DR2 objects with an unreasonably large parallax error as well as the questionable method for calculating the likely spatial distance between the components of the assumed physical pairs. The in EB19 reported discovery of a specific equal mass “twin” binary population seems to be a consequence of a questionable method for estimating star masses and can besides the caveats regarding the EB18 data for this reason not be confirmed. A moderate excess of very similar to equal mass pairs seems simply a consequence of the frequency of star masses in the selected star population – the most frequent masses have for obvious reasons a larger chance to be combined in a pair than other masses.

small contamination rate of less than 0.2 percent Introduction (means with an extremely small number of false posi- The recently pre-published EB19 paper (26 June tives). After a first look at this paper and the provided 2019, arXiv:1906.10128v1) on the detection of an equal data, mainly for counter-checking with the Knapp and mass binaries population referring to the EB18 catalog Nanson HPMS3 report including also some newly de- data reminded me that in July 2018 Brian Skiff had tected physical pairs based on GAIA DR2 data just sub- made me aware of the highly interesting EB18 paper mitted to JDSO, it was despite some open questions not then just pre-published (submitted to arXiv on 16 Jul checked in detail due to other ongoing projects. 2018 and published on 9 Aug 2018 in MNRAS) report- As the recent EB19 paper on the detection of an ing the identification of over 55,000 physical double excess of equal mass “twin” binaries also posed some stars in the solar neighborhood (less than 200 parsecs questions, I decided to give both papers a closer look, distance from the solar system) selected from GAIA starting with EB18 as base for EB19. DR2, primarily on the basis of common proper motion The EB18 catalog is mentioned in the report as be- and common parallax with the claim of an extremely

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 191

Counter-Check of Binaries Reported to be Detected in Gaia DR2 as well as an Equal Mass “Twin” Binary ...

ing available online, but without giving any specific with source_id2 453570059955151232 download information. Just a look at the personal El- • Projected separation between the components Badry webpage provides the necessary information for smaller than 50,000 AU or ~0.25 parsec – This downloading the catalog, which is meanwhile available seems a rather rigid cut compared to the ~1 par- in a second version from 12 Sep 2018 with one of the sec distance considered in several papers (Jiang selection criteria removed, changing the number of ob- and Tremaine 2010, Knapp 2019, Kamdar et al. jects from 55,128 to 55,507. The additional objects are 2019) as reasonable cut for potential binaries. not marked as such and spread over the full list, so ob- But, on the other hand, other authors like ject numbering is a bit unclear. All these issues raise the Kouwenhoven et al. 2010 also postulate a semi- question; if this catalog can be considered to be pub- major axis of less than 0.1 parsec as requirement lished in a regular way. To get a clear reference, I add- for an at least moderately stable binary. What at ed to the EB18 catalog, v1, a column with a running ID first looks like an effective criterion gets quickly number up to 55,128, identified then the additional ob- suspect by the crude attempt to calculate the spa- jects in v2 and added them to the list v1 starting with tial separation between the components of a bina- running ID number 55,129 up to 55,507. ry by applying the angular separation in arcsec- This research is done during the summer 2019 with onds θ on the distance of the primary in parsecs the EB18 objects still not included in the WDS or as θ x (1/ω) with ω for the parallax. It is very sur- WDSS catalog. As I had meanwhile published in prising that the Gaia DR2 data is obviously taken DSSC27 a list with >4,000 most likely physicals also very seriously when selecting objects, but is based on GAIA DR2 data it was also interesting to find more or less completely neglected for binary as- out how different methods using the same GAIA DR2 sessment by ignoring the parallax for the second- data set worked and why they produced different results ary as well as the given parallax error. This is (see Appendix B). most obvious in the mentioned cases with parallax values for the secondaries far below 5 mas Critical Examination of the EB18 Catalog making the idea that such a pair with a distance The criteria for selecting pairs from GAIA DR2 delta of 100 parsec or more might be a binary were basically looking for objects with parallax >5 with rather absurd (see example mentioned above) a parallax error <5% (“We search for companions • Proper motion diﬀerences within 3σ of the maxi- around stars that are nearby and have precise parallax- mum velocity diﬀerence expected for a system of es, parallax > 5 and parallax_over_error > 20”) with a total 5 Sun mass with circular orbit – Questiona- second object nearby within 50,000 AU using addition- ble from the very beginning as common proper al cut criteria to eliminate objects with questionable motion is no longer to be considered a necessary data quality. While all such criteria and cuts are prone criterion for physical pairs (Knapp 2019), but to discussion, some details are particularly noticeable: oddest is the 5 solar mass assumption, as nearly • Parallax error <5% for the primary - At first look all objects are reported to be between 0.3 and 1.3 rather restrictive, but in effect far too generous Sun masses. The authors are obviously aware of because parallax errors in the dimension near 5% this oddity and eliminated this criterion for the cause a huge spread in the calculated distance above mentioned version v2 of the catalog. with enhanced risk of false positives when look- • Additional data quality cuts regarding the pho- ing for likely binaries tometry values for both components are applied • Parallax error <20% for the secondary - Surpris- as the position on the CMD (color-magnitude ingly the <5% requirement is changed when diagram) is used to estimate the mass for all ob- looking for a potential secondary, allowing for a jects by interpolating on a grid of isochrones. much larger parallax error thus adding 1,585 Surprisingly the parallax of the brighter star is highly questionable objects to the EB18 catalog also assigned to the assumed companion, thus v1 and an additional 195 to EB18 v2 – there are ignoring again existing GAIA DR2 data. The certainly no good reasons to have different re- reason for such a procedure remains unclear. The quirements for primaries and secondaries. Also, a EB18 authors themselves state “These mass esti- bit surprisingly, is the fact that 2,332 secondaries mates are crude …” but believe that they are in have a parallax value below 5 mas. While it most cases accurate within 0.1 M. The estimat- might be sensible for primaries with parallax ed masses are, according to the EB18 paper, also close to 5 mas to look for secondaries with paral- used to declare the component with the larger lax slightly below 5 mas, but certainly not down mass as primary. This claim makes a bit cautious to 3.23 mas as is the case with the EB18 object

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 192

Counter-Check of Binaries Reported to be Detected in Gaia DR2 as well as an Equal Mass “Twin” Binary ...

Obj source_id1 source_id2 Sep PA WDS Disc C WDS Sep WDS PA 2 2871944820092678144 2871944820092678272 3.34520 54.99 23415+3247 ES 2327 3.35 54.9 5 2872283263515298432 2872283740256668416 112.35477 194.521 23320+3221 UC 4977 112.35 194.5 6 2872384074987802112 2872384281146232064 9.16626 138.009 23336+3234 OSO 199 AB 9.17 138.0 10 2872630399952398848 2872630399952398720 14.43348 62.576 23337+3316 LDS5102 14.40 242.5 14 2872975234286502272 2872974856329379968 36.60679 71.61 23392+3426 KPP3396 36.61 251.6 19 2873177681863201920 2873177681866528384 3.57084 166.619 23372+3439 HO 201 3.57 346.5 21 2847106611901400192 2847106646261138176 9.28754 193.27 00074+2219 CVR 304 9.29 13.2 24 2873451352884905344 2873451357179959680 24.58191 14.896 00033+3103 CRB 24 24.60 194.9 39 2875142745366475264 2875142749661298560 4.79736 243.448 00033+3357 ES 2209 4.80 243.4 52 2876526931721385344 2876526931721384960 10.27108 171.493 00144+3609 LDS3140 10.27 171.4

Content description: Obj = Running EB18_v1 number source_id1 = GAIA DR2 source id for primary source_id2 = GAIA DR2 source id for secondary Sep = EB18_v1 angular separation PA = EB18_v1 position angle WDS = WDS ID Disc = WDS discoverer code C = WDS components WDS Sep = WDS angular separation WDS PA = WDS position angle

Table 1: Cross-match EB18_v1 with WDS catalog (stub from download file)

because there are too many cases (to be precise for “visibility_periods_used” <9 and “duplicated 43.7%) with the fainter star as primary, contra- source” =1 was neglected. To ignore the GAIA dicting the general expectation that at similar DR2 field “duplicated_source” means accepting distance main sequence stars with larger mass potentially duplicated light sources indicating should also be brighter multiples not resolved by GAIA (see also Appen- • Usually, the brighter star of a pair is designated dix B). as primary based on the assumption that with similar distance the brightness of the components Side remarks for Table 1: reflects most often also the mass of the stars. – • A good part of the matched objects come with This convention, as already mentioned above, is reversed PA due to switched components for pri- ignored in the EB18 catalog. This is especially mary/secondary irritating for cross-matching with the WDS cata- • WDS LDS 215 and LDS6215 are ident log (a routine task for double star astronomers • WDS LDS 832 and TVB 18 might be identical but neglected by the EB18 authors), which there- with inverse components fore has to be done twice for the positions of the • Eliminated objects after initial cross-check result primary as well as the secondary. Using the with a 5 arcsecond search radius around the coor- WDS catalog per July 2019 as reference, there dinates for primaries and secondaries: are more than 20% of the EB18 objects listed as  Double matches due to search via primary and WDS pairs including a few hundred added to the secondary with separations smaller than the WDS catalog since July 2018. Table 1 lists as search radius of 5" stub the first 10 out of 11,202 positively matched  Matches with delta PA >20 compared to the objects available for download from the JDSO WDS value (considering also reversed com- website as flat text file “WDS X EB18_v1” ponents) • The EB18 catalog is intended to be a pure dou-  Matches with delta in angular separation bles catalog, so all multiples as well as clusters >25% from the WDS value were eliminated by the authors. Surprisingly the most basic GAIA DR2 data quality check sug- An assessment of the EB18 v1 objects with the gested by the GAIA team (Arenou et al. 2018) scheme according to Knapp 2019 results in 32,999 or

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 193

Counter-Check of Binaries Reported to be Detected in Gaia DR2 as well as an Equal Mass “Twin” Binary ...

Obj source_id1 source_id2 Sep PA BCD_AU_1_2 RCD_AU_1_2 WCD_AU_1_2 PlxS s_AU 1 2872017143044576896 2872017147341819904 16.42602 115.958 2,796.74 292,559.32 1,059,605.55 20 2,814.80 2 2871944820092678144 2871944820092678272 3.34520 234.990 563,011.53 1,377,568.56 2,190,716.37 1 660.44 3 2846735178834441856 2846735178834442368 6.42001 26.531 882,128.79 3,000,878.16 5,081,478.37 1 1,185.44 4 2846483566765789056 2846485039939110272 23.74313 90.053 4,396.42 230,748.06 1,494,720.43 20 4,443.08 6 2872384074987802112 2872384281146232064 9.16626 318.009 1,670.35 223,020.41 658,351.46 20 1,666.72 7 2872379264624690304 2872379264624690432 5.82210 112.488 804.13 245,794.06 985,230.99 20 811.84 8 2872309033319137792 2872308792800972160 123.26979 118.342 24,179.08 307,841.37 819,985.03 20 24,346.18 11 2872663591459404032 2872663591459403776 20.62646 323.294 305,580.45 701,158.67 1,097,453.20 1 3,002.22 12 2872803057638197120 2872803057638196608 17.92730 46.944 92,699.80 1,099,818.55 2,145,871.87 20 2,894.65 13 2872912184166813440 2872912179872035584 2.15982 89.651 432.92 1,123,801.67 2,763,248.61 20 431.79

Content description: Obj = Running EB18 object number (1-55128 for v1 and 55,129 to 55,507 for additional v2 objects) source_id1 = GAIA DR2 source id for the primary Plx1 = Plx primary in mas Plx1_e = Plx error for the primary *Gmag1 = Gmag primary source_id2 = GAIA DR2 source id for the secondary Plx2 = Plx secondary in mas Plx2_e = Plx error for the secondary *Gmag2 = Gmag secondary Sep = Angular separation in arcseconds PA = Position angle *BCD_LY_1 = Best case distance primary from Sun in lightyears calculated from Sep and Plx using +/- 1xPlx_e to minimize the spatial distance between the components within this range *BCD_LY_2 = Best case distance secondary from Sun in lightyears calculated from Sep and Plx using +/- 1xPlx_e to minimize the spatial distance between the components within this range BCD_AU_1_2 = Best case distance between the components in AU *RCD_LY_1 = Realistic case distance primary from Sun in lightyears calculated from Sep and Plx as given *RCD_LY_2 = Realistic case distance secondary from Sun in lightyears calculated from Sep and Plx as given RCD_AU_1_2 = Realistic case distance between the components in AU *WCD_LY_1 = Worst case distance primary from Sun in lightyears calculated from Sep and Plx using +/- 1xPlx_e to maximize the spatial distance between the components within this range *WCD_LY_2 = Worst case distance secondary from Sun in lightyears calculated from Sep and Plx using +/- 1xPlx_e to maximize the spatial distance between the components within this range WCD_AU_1_2 = Worst case distance between the components in AU PlxS = Parallax score between 0 and 100 depending on best/realistic/worst case distance <200,000 AU and Plx error as estimated likelihood for potential gravitational relationship s_AU = EB18 distance between the components in AU Values with “ * ” are not listed in Table 2 but are available in the download file

Table 2: EB18_v1 likely opticals (stub from download file)

~60% of the reported pairs as likely opticals although in such cases the spatial distance “s_AU” given in this scheme accepts similar to EB18 parallax errors up EB18 is quite close to the best case distance to 5% for a positive rating. Table 2 gives a stub of such “BCD_AU_1_2”, but the realistic case distance using objects, the full list is available for download from the the given parallaxes without considering the given er- JDSO website as flat text file “EB18 likely opticals”. rors is larger than 200,000 AU or ~1 parsec. A “PlxS” The column “PlxS” gives an indication for the like- value of 1 indicates a likelihood of near zero (but cer- lihood for a distance between the components smaller tainly below 10%) as the parallaxes do not even overlap than 200,000 AU (~1 parsec) using the angular separa- within the given error range. tion as well as the given Gaia DR2 parallax and paral- A rather precise likelihood can be derived by a lax error data. A value of 20 suggests a likelihood of Monte-Carlo simulation using the given GAIA DR2 ~20% (but certainly far below 50%) for such cases with data for RA, Dec and parallax as mean values and the parallaxes overlapping within the given parallax error – given error as standard deviation for a normal distribu-

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 194

Counter-Check of Binaries Reported to be Detected in Gaia DR2 as well as an Equal Mass “Twin” Binary ...

tion (see Appendix A). To give an impression such a The simulation examples show very clearly that the simulation is done for a few objects in table 2 with a EB18 spatial distance values s_AU correspond closely sample size of 120,000: with the smallest simulations results – but these come Obj 1 with PlxS=20: Smallest distance of the simu- only with an extremely small likelihood close to zero lation results is 2,775 AU, the percentile 16 value is and the more realistic median distance values are in all already ~139,000 AU and the median distance is these cases far too large to allow for gravitational rela- ~455,000 AU. The rather large parallax errors cause a tionship. very flat distribution with a huge spread and the likeli- My scheme for assessing assumed binaries (Knapp hood for a distance <200,000 AU is 23%. 2018) works fine with reasonable small parallax errors, Obj 2 with PlxS=1: Smallest distance of the simula- but it allows similar to EB18 parallax errors up to 5% tion results is 679 AU but already the percentile 16 val- for a positive rating. When developing this scheme, my ue is with ~805,000 AU far outside the cut value of expectation was that combining data with normal dis- 200,000 AU and the median distance is with tributed error range should result in a normal distribu- ~3,917,000 AU quite huge. The rather large parallax tion with the combined mean as average. While this errors cause a very flat distribution with a huge spread worked out very well with very small relative errors, I and the likelihood for a distance <200,000 AU is 2%. had with my first Monte-Carlo simulation runs to real- Obj 3 with PlxS=1: Smallest distance of the simula- ize that even moderately large parallax errors produce a tion results is 1,117 AU but median distance is with huge spread resulting in very flat distributions with ~9,317,000 AU more than huge. The very large paral- mean/median values; far larger than the spatial distance lax errors cause an extremely flat distribution with a between the components calculated from parallaxes and huge spread and the likelihood for a distance <200,000 angular separation without errors. Meanwhile, it is clear AU is again 2%. that the cut for parallax errors has to be reduced by a Obj 6: with PlxS=20: Smallest distance of the simu- factor ~10 to get reliable results. This means that ob- lation results is 1,665 AU and median distance misses jects with parallax error up to 0.5%, and with some al- with ~278,000 AU the cut by 40%. The large parallax lowance up to 1%, are correctly assessed with a median error for the primary causes a large spread and the like- simulation distance close to the calculated “realistic lihood for a distance <200,000 AU is 37%. A case for a case distance” but with larger parallax errors the medi- might be binary - future GAIA data releases might pro- an distance of the simulation is due to the large spread vide a parallax for the primary with a smaller error al- mostly outside the 200,000 AU range. For this reason it lowing for a more conclusive assessment. is necessary to have also a closer look at the objects Obj 13 with PlxS=20: Smallest distance of the sim- with PlxS value ~80 indicating falsely that the calculat- ulation results is 434 AU but median distance is with ed RCD_AU_1_2 values of less than 200,000 AU ~1,197,000 AU rather huge. The large parallax errors should be near the median value of a simulation run. cause a very flat distribution with a huge spread and the Table 3 gives several examples of such seemingly good likelihood for a distance <200,000 AU is 9%. pairs as a stub, the full list of 3,920 such objects is

Obj source_id1 source_id2 Sep PA BCD_AU_1_2 RCD_AU_1_2 WCD_AU_1_2 PlxS s_AU PlxE

14 2872975234286502272 2872974856329379968 36.60679 251.610 3,234.61 132,102.41 590,404.44 80 3,245.96 C

17 2873172974582491904 2873172630984993408 209.33177 238.590 38,912.74 157,914.76 1,043,049.97 80 39,194.29 C

35 2874298805767507328 2874298767112458752 4.50143 158.628 760.33 179,607.34 1,587,385.70 80 769.90 D

51 2876373343690310144 2876373343690310016 3.78342 301.144 508.63 191,584.98 933,052.87 80 513.45 C

57 2876697252944594176 2876697252944594048 2.24872 261.778 299.79 5,457.75 909,993.78 80 303.58 D

64 2877347339194412416 2877347339194412800 7.81695 201.379 1,323.75 184,235.12 911,128.14 80 1,322.95 C

81 2879327112958858880 2879327319119080832 152.73209 23.427 21,719.18 59,375.62 858,334.79 80 21,984.84 C

110 2881998960574720256 2881998956279420288 6.47185 273.745 1,159.71 9,488.82 1,377,482.29 80 1,173.98 D

118 2865994709839871872 2865993232369137920 24.55551 234.106 1,092.73 101,562.63 324,366.40 80 1,097.90 C

123 2866270893416092032 2866270893416091520 13.62311 25.390 1,462.20 185,084.20 837,406.62 80 1,468.76 D

Content description: Ident with Table 2 plus additional column PlxE with rating for the relative Plx (C for >1% and D for >1.5%)

Table 3: EB18_v1 objects likely optical despite Plx Score 80 rendered questionable by large parallax errors (stub from download file)

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 195

Counter-Check of Binaries Reported to be Detected in Gaia DR2 as well as an Equal Mass “Twin” Binary ...

Obj source_id1 source_id2 Sep PA BCD_AU_1_2 RCD_AU_1_2 WCD_AU_1_2 PlxS s_AU 5 2872283263515298432 2872283740256668416 112.35478 14.521 6,167.61 30,794.37 98,604.65 100 6,186.68 9 2872313706243670656 2872313706243670400 13.00470 350.594 1,400.24 69,845.60 266,163.53 80 1,404.81 10 2872630399952398848 2872630399952398720 14.43348 242.576 734.66 43,373.89 115,286.47 100 737.19 19 2873177681863201920 2873177681866528384 3.57084 346.619 407.78 74,333.27 296,233.95 80 409.80 29 2873926105685136640 2873926105685136768 3.04193 218.904 410.99 136,934.46 571,862.18 80 410.70 36 2874596429820987264 2874596429820987520 6.87615 176.107 869.10 137,093.28 441,583.30 80 868.13 37 2874788432038781312 2874788432038781440 3.04745 101.571 544.22 96,712.26 582,079.56 80 545.78 38 2875031527188163072 2875033176455625856 199.25836 37.354 16,400.53 26,040.50 118,477.55 100 16,426.52 40 2874952018753440128 2874952018753440000 2.95796 50.103 450.15 78,981.92 339,651.24 80 450.59 41 2875236719249747712 2875236723545613952 15.44426 318.081 1,173.39 14,156.73 157,550.91 100 1,175.52

Content description identical with Table 2.

Table 4: EB18_v1 objects likely physicals (stub from download file)

available for download from the JDSO website as flat on this list again with a sample size of 120,000: text file “EB18_v1_seemingly_good”. This means also Obj 5 with a PLxS value of 100: Smallest spatial that additional 3,920 or ~7% of the EB18 v1 catalog are distance between the components 6,143 AU and medi- also likely optical pairs raising the percentage of most an distance 39,764 AU with 100% likelihood for a dis- likely EB18 opticals to 67%. tance less than 200,000 AU with the exception of only a To demonstrate the effect of large parallax errors, I few outliers up to ~244,000 AU. ran the Monte-Carlo simulation for the first 3 objects on Obj 9 with PlxS 80: Smallest distance of the simu- this list: lation results is 1,396 AU and median distance is Obj 14: Smallest distance of the simulation results ~109,108 AU – about 50% larger than the calculated is 3,225 AU but median distance is already ~277,344 RCD_AU_1_2 distance. The moderate parallax errors AU – more than double the calculated RCD_AU_1_2 for both the primary and the secondary cause some distance. The large parallax error for the secondary of spread and the likelihood for a distance <200,000 AU is ~2.1% causes despite the rather small parallax error for 79%. the secondary a large spread and the likelihood for a Obj 10 with PlxS 100: Smallest distance of the sim- distance <200,000 AU is 38%. ulation results is 732 AU and the median distance is Obj 17: Smallest distance of the simulation results ~48,053 AU – quite close to the calculated is 38,487 AU but median distance is already ~471,349 RCD_AU_1_2 distance. The small parallax errors for AU – about triple the calculated RCD_AU_1_2 dis- both the primary and the secondary of ~0.35 cause a tance. The rather large parallax error for the secondary relative small spread and the likelihood for a distance of ~1.6% causes combined with the median large paral- <200,000 AU is 100% with only a few outliers up to lax error of ~0.7% for the primary a corresponding ~283,000 AU. Figure 1 shows the distribution of the large spread and the likelihood for a distance <200,000 simulation sample for the spatial distance: AU is 22%. Despite all EB18 efforts to estimate star masses Obj 35: Smallest distance of the simulation results based on their color-magnitude diagram position no

is 756 AU but median distance is already ~709,035 AU – about 4 times the calculated RCD_AU_1_2 distance. The rather large parallax error for the secondary of ~2.7% causes combined with the large parallax error of ~1.3% for the primary a huge spread and the likelihood for a distance <200,000 AU is only 15%.

The remaining 18,209 EB18_v1 objects are rated with PlxS 100 or 80 but with parallax error smaller than 1%. Table 4 is a stub of 10 objects from the full list available for download form the JDSO website as flat text file “EB18_v1_likely_physicals”. To demonstrate the effect of small parallax errors I Figure 1. Distance between the components of Obj 10 in 1000 AU according to Monte-Carlo simulation with a sample size of run the Monte-Carlo simulation for the first 3 objects 120,000.

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 196

Counter-Check of Binaries Reported to be Detected in Gaia DR2 as well as an Equal Mass “Twin” Binary ...

such values are given in the EB18 catalog so it is im- possible to repeat the given conclusions. To compen- sate for this lack of data I looked up the mass50 (means percentile 50 mass) values in the Anders et al. 2019 GAIA DR2 StarHorse (in the following StarHorse) catalog. I would have preferred to cross-match the full EB18 catalog with the StarHorse catalog but the GAIA.AIP query interface hosted by the “Leibniz- Institute for Astrophysics Potsdam” does not offer the possibility to use large object lists (at least I did not find it and the help desk was due to the university holiday season not available) so I had to operate with many queries for small parts of the EB18 catalog of about 250 Figure 2. Distribution of StarHorse mass50 for primary and sec- objects and I decided to restrict my efforts to a repre- ondary in percent of the EB18_v1 sample. sentative ~10% sample by selecting by chance 5 bins with 1,000 EB18_v1 objects each and got in total 4,810 es 0.3 ≤ M/M ≤ 1.3”. matches with values for both components. A first look made clear that EB18 primaries were Table 5 gives a stub for the first 10 of the EB18 often (to be precise >47%) the stars with the smaller objects cross-matched with the StarHorse catalog, the StarHorse mass50 value with the latter corresponding full list is available for download from the JDSO web- very well also with the brightness of the stars (with on- site as flat text file “EB18_v1_mass50”: ly a few exceptions mostly for pairs with nearly ident Most interestingly the distribution of masses for brightness) means larger mass for the brighter stars. primary and secondary is quite different with a clear Taking in consequence the stars with the larger mass50 peak near the average 0.44 M value for the secondary value as primaries resulted in a minimum mass of 0.12 compared to a much larger spread for the primary. The M and a maximum mass of 3.10 M. Average value distribution for the primary shows a dent in the 0.7 and for the primary is 0.72 M with standard deviation of 0.8 mass50 bin suggesting an irregularity caused may 0.33 M. Average value for the secondary is 0.44 M be by a bias in the EB18 object selection process (see with standard deviation of 0.22 M with a minimum Figure 2 and compare with Figure 13). mass of 0.11 M and a maximum mass of 2.31 M. Figure 5 in EB18 (shown here as Figure 3) shows These numbers do not match very well with the EB18- the mass ratio distribution of the EB18 pairs (black line statement “Most of the main-sequence stars have mass- for main sequence pairs) – steep increase from small

Obj source_id1 mass50_1 Gmag1 source_id2 mass50_2 Gmag2 1 2872017143044576896 0.79240966 12.119735 2872017147341819904 0.37382376 16.622170 3 2846735178834441856 0.39968893 16.502570 2846735178834442368 0.19929305 17.984964 4 2846483566765789056 1.88280869 8.157404 2846485039939110272 0.30255136 17.368803 5 2872283263515298432 0.32529020 14.360177 2872283740256668416 0.70147246 10.459101 6 2872384074987802112 0.35074097 15.618967 2872384281146232064 0.60082656 13.138443 7 2872379264624690304 0.42372254 15.743548 2872379264624690432 0.27287805 17.105940 8 2872309033319137792 0.79839927 12.309546 2872308792800972160 0.56184644 14.558531 9 2872313706243670656 0.60056657 13.318013 2872313706243670400 0.50094569 14.433413 10 2872630399952398848 0.30996296 14.524491 2872630399952398720 0.30038962 14.604014 11 2872663591459404032 0.63140053 13.939705 2872663591459403776 0.45031360 15.235794

Content description Obj = Running EB18 object number (1-55128 for v1 and 55,129 to 55,507 for additional v2 objects) source_id1 = GAIA DR2 source id for the primary mass50_1 = Mass50 value for the primary from the Anders et al. 2019 GAIA DR2 StarHorse catalog Gmag1 = GAIA DR2 Gmag for the primary source_id2 = GAIA DR2 source id for the secondary mass50_2 = Mass50 value for the secondary from the Anders et al. 2019 GAIA DR2 StarHorse catalog Gmag2 = GAIA DR2 Gmag for the secondary

Table 5: StarHorse mass50 values for a sample of EB18_v1 objects (stub from download file)

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 197

Counter-Check of Binaries Reported to be Detected in Gaia DR2 as well as an Equal Mass “Twin” Binary ...

• The method for calculating the spatial distance between the components of pairs provides consistently completely unrealistic best case result by ignoring the GAIA DR2 parallax value of the secondary as well as the parallax errors for primary and secondary • Star masses are estimated by their position in a color-magnitude diagram but the absolute magnitude for the companions is calculated with the same parallax value as for the brighter component ignoring again existing precise GAIA DR2 data • The stars with the larger mass in a pair are selected as primaries but a very high percentage of the primaries are fainter than the assumed secondaries – rather not to expect for main sequence pairs. This puts an overall question mark on the star Figure 3. Clipping from EB18 Figure 5: q=m2/m1 cumulated mass estimation process (black line for MS/MS pairs) • No star mass values are provided making it im- possible to counter-check the reported results.

ratios with flat distribution for a ratio from 0.25 to 0.95 Resulting issues are: with a tiny spike in the end towards a ratio of 1. • Heavy contamination of the EB18 catalog with The reason for such a difference remains unclear – false positives – even if we concede that about the size of the sample of 4,810 provides a 1.86% mar- 25% of the 67% as likely opticals assessed EB18 gin of error with 99% confidence so sample size cannot objects might be very well binaries there remains be the problem. Another reason would be that the a contamination rate of >50% mass50 data from the StarHorse catalog are significant- • Spatial distance s_AU between the components ly inferior compared to the EB18 mass estimations – far too optimistic to the degree that these values this seems highly unlikely especially with the EB18 can be considered generally wrong issue regarding main sequence brightness/mass rela- • Estimated star mass values are not only not pro- tionship already discussed. vided but by the given evidence highly question- Summary of the Critical Examination of the able. EB18 Paper/Catalog Critical Examination of the EB19 Paper Overall points of concern are EB19 reports the discovery of an equal mass “twin” • The allowed parallax error for selecting objects binary population based on the EB18 catalog data with from the GAIA DR2 catalog is far too generous some additional cuts which seems to confirm “A puz- to meet the “very pure” claim

Figure 4. Distribution star mass ratio EB18_v1 StarHorse sample in 0.05 bins

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 198

Counter-Check of Binaries Reported to be Detected in Gaia DR2 as well as an Equal Mass “Twin” Binary ...

Figure 6. Distribution of mass ratios for EB19 StarHorse sample in 0.01 bins Figure 5. Clipping from EB19 Figure 7 suggesting a huge excess of equal mass binaries

zling feature of the mass ratio distribution identified by previous works … the so called ‘twin’ phenomenon … a purported statistical excess of nearly equal-mass binaries with mass ratios 0.95 ≲ q < 1”. The most important additional quality cuts are as follows: • Restriction to main sequence pairs • Restriction to pairs with parallax error size <5% also for the secondary

• Restriction to a mass range up to 2.5M Figure 7. Distribution of mass ratios for EB19 StarHorse sample in 0.05 bins While the restriction to assumed main sequence pairs looks reasonable the decision to eliminate the pairs with secondaries not meeting the criteria applied ple using the higher mass50 value as primary is shown for the primaries looks like a late acknowledgement in Figure 6 using 1% bins. that it was from the very beginning questionable to ap- The same data presented in 0.05 bins is likely better ply different selection criteria for primaries and second- to compare with EB19 Figure 7. aries in EB18. This distribution of mass ratios is definitely very Figure 7 from the EB19 paper (shown here in Fig- different from the distribution suggested in EB19 Fig- ure 5) suggests a noticeable excess of equal-mass pairs ure 7. There is no steep increase but beginning with a after applying the additional quality cuts on the EB18 mass ratio of ~0.15 this looks similar to the EB18_v1 data but again no mass data values are provided, only StarHorse sample rather like a linear increase of star several graphs with color-magnitude diagrams. This mass ratios with a small spike at the end. But can this figure is by the way very similar to figure 2 from Moe spike considered to be a significant excess of “twin” and Di Stefano 2017. pairs with similar mass? As no star mass data is published the EB19 results In my opinion not because if the star masses of the cannot be repeated independently so I had again to take components of pairs are considered to be determined by resort with the StarHorse catalog this time including the a random process then we get the same statistical effect. EB18_v2 data as this release is obviously the base used When merging two random processes with a given for EB19. This added 49 v2 objects to the list but the mean value then masses near the mean value occur de- application of the additional EB19 cuts mentioned pending on the given standard deviation more often above reduced the total number of the sample to 4,432 than masses very different form the mean value and for means a sample size still >10% of the EB19 data. this reason a spike of “twins” is purely the expected As the data for the first 10 objects is identical with result of such a random process. Table 5 no stub is given here but the full list is available If we combine the EB19 StarHorse sample data for for download from the JDSO website as flat text file an overall star population we get an average mass of “EB18_v2_mass50_ex_cuts”. In the following this data 0.59M with a standard deviation of 0.31 (see Figure set is referred to as EB19 StarHorse sample. 8). The mass ratio distribution based on this data sam- Using this data set for a random selection of ~4,500

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 199

Counter-Check of Binaries Reported to be Detected in Gaia DR2 as well as an Equal Mass “Twin” Binary ...

pairs we get the following distribution very similar to the pattern shown in Figure 2 for the EB18_v1 Star- Horse mass50 sample. Interestingly even the dent for the masses 0.7 and 0.8 M is replicated if a bit weaker. This results in a mass ratio distribution for random pairs based on the EB19 star population as shown in Figure 10. The spike at the end of Figure 10 with the random sample might be less pronounced than in Figure 6 with the EB19 StarHorse data set but it seems highly questionable if this difference is statistically significant enough to allow for the conclusion that there is such a

Figure 8. mass50 distribution in EB19 StarHorse sample thing as an equal-mass “twin” population. The 99% confidence interval for the 5.39% spike in Figure 6 is 0.88% and the 99% confidence interval for the 3.06% spike in graph 9 is 0.67%. While this means that both spikes do not overlap even within their 99% confidence intervals with a gap of 0.74% remaining, such a tiny gap seems to me not significant enough for serious conclusions. To eliminate any misgivings about using the given EB19 StarHorse mass50 distribution, I drew a random sample of an arbitrary number of 1,977 GAIA DR2 star pairs using the GAIA random index, matched with the

Figure 9. Random pair mass50 distribution for primary and sec- corresponding StarHorse mass50 values, made the larg- ondary based on EB19 StarHorse star population er mass star the primary and calculated the mass ratio for each pair. What I got is shown in Figure 11. This time the peak value is 4.1% with a 99% confidence interval of 1.15% covering the EB19 StarHorse sample as well as the random sample based on EB19 StarHorse data pool. No data set is given for this example as it can be easily reproduced with existing tools publicly available. I consider these random results as proof that the EB19 mass ratio distribution corresponds with the distribution in random samples and that there is no such thing as an excess in “twin” binaries with other than

pure statistical reason – at least when the mass50 Star- Figure 10. Random sample mass ratio distribution in 0.01 bins Horse catalog data is considered to be more reliable (based on EB19 StarHorse sample star population) than the not publicly available EB18 mass estimations. So far the results by just looking at the numbers - another question is the EB19 mass data quality based on the EB18 data catalog. Despite the “enhancements” of EB18 data by applying additional quality cuts it remains still an unresolved riddle why it was considered appropriate to use an obviously highly contaminated date source for extensive statistical processing. Highly contaminated not only due to the huge part of false binary positives but also for the following reasons: • The EB18 authors themselves consider their mass estimations as “crude” • The parallax for the secondaries was intentional- ly falsely – by ignoring existing GAIA DR2 data Figure 11: GAIA DR2 random sample mass ratio distribution in 0.01 bins

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 200

Counter-Check of Binaries Reported to be Detected in Gaia DR2 as well as an Equal Mass “Twin” Binary ...

KPP+ source_id1 mass50_1 source_id2 mass50_2 q 1 2341739525536269568 0.54917818 2341739525536269440 0.54917598 0.99999599 2 4922504834475892480 0.49068627 4922504834475011072 0.25059149 0.51069595 3 420485136603049088 0.78688747 420485136593782912 0.74453515 0.94617741 4 2746869015880925824 0.78168672 2746869015880925696 0.59936732 0.76676155 5 2306711382881486208 0.65043151 2306711181018700800 0.44966626 0.69133530 6 4923573765936638208 0.69848222 4923573765936638464 0.64902496 0.92919324 10 396259489527418368 0.70071042 396259459468383744 0.69816643 0.99636941 11 4689746567995853952 0.85447359 4689746537932710656 0.55178142 0.64575597 12 4922464805380607360 0.44927859 4922464805379529600 0.20058107 0.44645143 14 4901424344713245184 0.89591235 4901424344713244928 0.60024953 0.66998689

Content description: KPP+ = Running object number from Knapp 2019/DSSC 27 source_id1 = GAIA DR2 source id for primary mass50_1 = GAIA DR2 StarHorse mass50 for primary source_id2 = GAIA DR2 source id for secondary mass50_2 = GAIA DR2 StarHorse mass50 for secondary q = Mass ratio

Table 6: KPP objects sample

– considered ident with the parallax for the pri- ination of all (visible) multiples as well as all objects maries to calculate the absolute magnitude for with potential duplicity issues and with less than 9 visi- their position on the color-magnitude diagram bility_periods_used 3,270 most likely physical pairs used for estimating the masses of stars. remaining considered being (despite a large overlap with the EB18 catalog, see Appendix B) without con- At least to some degree the authors of EB19 seem tamination with false positives and potentially unre- to be aware that some caution is appropriate by stating solved multiples. For all objects the 50 percentile mass “In modeling the mass ratio distribution, it is not criti- value from the GAIA DR2 StarHorse catalog was cal that the mass ratio of any binary be measured accu- matched if available with remaining 2,842 pairs with rately, but rather that the distribution of magnitude dif- mass50 values for both components and the mass ratio ference be predicted self-consistently” – in simple was calculated. Table 6 gives the data for the first 10 words this means that it is for the authors not important objects as stub, the full data set is available for down- if the data is questionable but that the results seem rea- load from the JDSO website as flat text file sonable. I am not sure if I can subscribe to such an ap- “KPP_objects_sample”. proach – more appropriate to me seems the concept that flawed input data produces most likely flawed output (garbage in, garbage out). Finally there remains the scenario that the EB19 mass ration distribution is similar to a random sample only because of the high contamination rate of the EB18 catalog despite the additional cuts and that a “twin” binaries excess exists very well in a pure binaries data set. To check this scenario I have a look at a GAIA DR2 binaries set I trust to show very little contamination – this means a counter-check with KPP objects from Knapp 2019/DSSC 27 based on GAIA DR2 ob-

jects with a parallax error of less than 0.5%. After elim- Figure 12. Distribution mass ratio in 0.01 steps for a pure binaries data set

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 201

Counter-Check of Binaries Reported to be Detected in Gaia DR2 as well as an Equal Mass “Twin” Binary ...

A first look at the mass ratio of these objects seems I/347 “Distances to 1.33 billion stars in Gaia DR2” cat- to support the impression of an excess of pairs with alog results in a spread up to +/- 10 parsecs – obviously similar mass this time even with a peak value of 8.43% such objects are of little significance when looking for (see Figure 12). binaries. A closer look at the frequency of component mass- The use of the likely highly contaminated EB18 es shows a peak for the primaries at 0.68 M with a catalog for EB19 seems despite additional data quality standard deviation of 0.24 and for the secondaries at cuts not such a good idea especially as the star mass 0.47 and 0.16 (see Figures 13 and 14) suggesting an estimation method applied seems also rather suspect as overlap of corresponding distribution of masses be- well. As no mass data are given I had to resort to a sam- tween 0.5 and 0.6 M. The comparison with the corre- ple of mass data from Anders et al. 2019 GAIA DR2 sponding values from the EB18_v1 data set (see Figure StarHorse catalog with the result that the EB19 result of 2) with an average value for the primary of 0.72 M an assumed “twin” binaries excess can be explained as with standard deviation of 0.33 M and an average val- simple statistical consequence when selecting star pairs ue for the secondary is 0.44 M with standard deviation by random from a given star population. of 0.22 M indicates not only closer mean values but Acknowledgements: especially also a significantly smaller standard devia- The following tools and resources have been used tion leading unavoidable to a larger number of nearly for this research: equal mass pairs. • Washington Double Star Catalog This clearly confirms again that the cause for an • CDS VizieR exponential trend towards similar mass pairs is simply a function of the mass frequency of the components in • GAIA DR2 catalog the given star population– values around the mean val- • Distances to 1.33 billion stars in Gaia DR2 cata- ue simply occur significantly more often than other log mass values so the probability of two components hav- • DSS and Pan-STARRS (PS1) images ing similar mass in this range is accordingly higher than • Aladin Sky Atlas for other combinations. • CDS TAP-VizieR and X-Match • GAIA DR2 StarHorse catalog Summary • Gaia@AIP Services hosted by the Leibniz- This report shows that the EB18 catalog has besides Institute for Astrophysics Potsdam (AIP) some other discussed shortcomings a huge contamination rate of likely >50% with false positives. The data References quality cut for the GAIA DR2 parallax values applied Anders, F., et al., 2019, “Photo-astrometric distances, for the EB18 catalog with parallax error up to 5% is extinctions, and astrophysical parameters for Gaia most likely the main reason for a noticeable ratio of DR2 stars brighter than G = 18”, Astronomy & As- questionable pairs reported far beyond the contamina- trophysics, 10.1051/0004-6361/201935765 tion rate estimated by the authors themselves. The cause is simply the massive spread in possible distances F. Arenou, et al., 2018, “Gaia Data Release 2: Cata- between the components caused by large parallax errors logue validation”, Astronomy & Astrophysics, 616, A17. (see Appendix A). Looking up objects with a parallax near 5 and parallax_over_error near 20 in the CDS

Figure 13. Mass50 distribution for the primaries in the Figure 14. Mass50 distribution for the secondaries in the KPP objects sample KPP objects sample

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 202

Counter-Check of Binaries Reported to be Detected in Gaia DR2 as well as an Equal Mass “Twin” Binary ...

Kareem El-Badry, et al., 2019, “Discovery of an equal- Knapp, W. and Nanson, J., 2019, “A Catalog of High mass "twin'' binary population reaching 1000+ AU Proper Motion Stars in the Southern Sky (HPMS3 separations”, arXiv:1906.10128v1. Catalog)”, Journal of Double Star Observations, 15 (1), 21-41. Kareem El-Badry and Hans-Walter Rix, 2018, “Imprints of white dwarf recoil in the separation Knapp, Wilfried R. A., 2019, “The ‘True’ Movement of distribution of Gaia wide binaries”, Monthly Notic- Double Stars in Space”, Journal of Double Star es of the Royal Astronomical Society, Advance Ar- Observations, 15 (3), 464-488. ticle Aug 9, 2018. Kouwenhoven, M.B.N, et al., 2010, “The formation of Moe, Maxwell & Di Stefano, Rosanne, 2017, “Mind very wide binaries during the star cluster dissolu- Your Ps and Qs: The Interrelation between Period tion phase”, Monthly Notices of the Royal Astro- (P) and Mass-ratio (Q) Distributions of Binary nomical Society, 404, 1835–1848. Stars”, The Astrophysical Journal Supplement Se- ries, 230:15 (55p). Knapp, Wilfried R.A., 2018, “A New Concept for Counter-Checking of Assumed Binaries”, Journal of Double Star Observations, 14 (3), 487-491.

Appendix A Description of the binary assessment scheme (according to Knapp 2018):

Based on the given GAIA DR2 values for parallax and parallax error the following scenarios for the distance between the components of a pair of stars in AU are calculated: • Best case distance: Smallest possible distance between the components using the given parallax values +/- given error range • Realistic case distance: Distance between the components using the given parallax values without considering the error range • Worst case distance: Largest possible distance between the components using the given parallax values +/- given error range • Next comes a letter based rating for the distance: "A" for worst case distance, "B" for realistic case distance and "C" for best case distance less than 200,000 AU and “D” for above • Next comes a letter based rating for the parallax error size "A" for Plx error less than 5% of Plx, "B" for less than 10%, "C" for less than 15% and “D” for above • The letter based scoring is then transformed into an estimated likelihood for a potential gravitational relationship (PGR)

Meanwhile it became clear that the expectation that the “realistic case distance” should correspond with the mean value of the distance after combining the parallax values as normal distributions with the given errors as standard deviation works only for parallax errors smaller by a factor 10 as given above. This means that the proposed assessment scheme works fine with parallax errors up to 0.5% and acceptable good up to 1%. Any error size above 1% leads to an increasing spread in the distance distribution making the “realistic case distance” value obso- lete.

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 203

Counter-Check of Binaries Reported to be Detected in Gaia DR2 as well as an Equal Mass “Twin” Binary ...

In the following figures this effect is shown in units of 1,000 AU for a pair with 6.42" angular separation and parallax 10 mas for both components with parallax errors 0.025/0.050/0.100/0.200.

Figures A1 to A4: Distance distribution with parallax errors 0.025/0.050/0.100/0.200

Description of the potential gravitational relationship assessment procedure based on Monte Carlo simulation (according to Knapp 2019): While the assessment scheme described above can be easily used for huge objects lists the following much more precise scheme needs to be applied step by step per single object: • GAIA DR2 values for RA/Dec and Plx are used for a Monte Carlo simulation assuming a normal distribution for these parameters with the given error range as standard deviation. The distance between the components is calculated from the inverted simulated parallax data and the simulated angular separation using the law of cosines with a and b = distance vectors for the stars A and B in lightyears calculated as (1000/Plx)*3.261631 and γ = angular separation in degrees calculated as • The likelihood for potential gravitational relationship (PGR) is the percentage of simulation results a22−+2 ab cos( ) b

<200,000 AU (~1 parsec) out of the simulation sample with a size of 120,000 • The smallest, median and largest distance is the smallest, median and largest result of the simulation sample,   =arccos sin(DE 1) sin( DE 2) + cos( DE 1) cos( DE 2) cos( RA 1 − RA 2 )

also percentile 16 or 84 or any other percentiles are easily to determine if required • The smallest/median/largest etc. distance might also used as estimation for the minimum value for the semimajor axis of a potential orbit allowing for the calculation of a smallest/median/largest etc. possible orbit period assuming zero inclination using the available star masses of primary and secondary (for example GAIA DR2 StarHorse mass16/50/84 values).

Appendix B Cross-match EB18 catalog with “Physical pairs found in GAIA DR2” (Knapp 2019)

In autumn 2018 (with the EB18 paper long forgotten) I worked on a paper “Physical pairs found in GAIA DR2” submitted to Bob Argyle end of November 2018 and published in DSSC27 in spring 2019. The objects were selected from GAIA DR2 with a parallax value >5mas and an angular separation up to 60 arcseconds. Final result were 4,217 objects found to be most likely physical by applying the assessment scheme described in Appendix A. Basically it is to expect that all these objects are already covered with the EB18 catalog but to be sure I cross- matched my list with the EB18_v2 catalog and got a positive match for 3,173 objects with about 50% of them with reversed primary/secondary. Table B1 lists the first 10 such objects as stub with the full list available for download from the JDSO website as flat text file “KPP_XX_EB18_v2”.

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 204

Counter-Check of Binaries Reported to be Detected in Gaia DR2 as well as an Equal Mass “Twin” Binary ...

KPP+ Obj source_id1 source_id2 Sep PA Plx1 e_Plx1 Plx2 e_Plx2 BCD AU RCD AU WCD AU PlxS

1 42492 2341739525536269568 2341739525536269440 4.61684 24.778 9.2362 0.0417 9.1584 0.0456 501.62 189715.33 402791.34 80

4 48938 2746869015880925824 2746869015880925696 4.84969 270.613 10.6021 0.0490 10.6156 0.0489 455.33 24746.04 204173.78 80

5 42567 2306711382881486208 2306711181018700800 9.48859 56.226 8.9474 0.0374 8.9395 0.0367 1057.11 20400.43 211455.28 80

6 7377 4923573765936638208 4923573765936638464 6.80564 166.112 9.3457 0.0244 9.3191 0.0426 726.98 63002.70 222118.16 80

10 35449 396259489527418368 396259459468383744 18.61237 177.283 7.3463 0.0301 7.3641 0.0306 2523.28 67915.30 299304.53 80

13 53174 4991245614249699456 4991245614249699584 5.09070 234.828 7.9640 0.0387 7.9396 0.0310 638.70 79599.12 306682.27 80

14 7395 4901424344713245184 4901424344713244928 2.84072 60.447 6.9153 0.0281 6.9360 0.0177 409.13 89020.31 286416.27 80

16 37772 420291656914875008 420290901000634112 38.68582 125.738 8.1796 0.0304 8.2113 0.0365 4712.14 97467.42 302629.22 80

17 7417 4904558330809468416 4904558330809468288 7.50102 39.693 5.6652 0.0274 5.6376 0.0228 1325.20 178256.70 502077.08 80

18 165 2849801721059508096 2849801721059507968 2.85337 356.977 11.7827 0.0382 11.7856 0.0582 241.39 4314.40 147251.08 100

Content description KPP+ = Running object number *Comp = Components (blank = AB) Obj = EB18 object number *WDS ID = WDS object ID in case of an overlap with WDS catalog *Disc Ref = Discoverer ID in case of an overlap with WDS catalog source_id1 = GAIA DR2 source id for primary source_id2 = GAIA DR2 source id for secondary Sep = Separation in arcseconds epoch 2015.5 *e_Sep = Error separation PA = Position angle epoch 2015.5 *e_PA = Error position angle Plx1 = Parallax value primary in mas e_Plx1 = Error parallax value primary Plx2 = Parallax value secondary in mas e_Plx2 = Error parallax value secondary BCD AU = Best case distance between components in AU RCD AU = Realistic case distance between components in AU WCD AU = Worst case distance between components in AU PlxS = Parallax score, estimated likelihood for potential gravitational relationship *v1 = GAIA DR2 visibility_periods_used primary *d1 = GAIA DR2 duplicated_source primary *v2 = GAIA DR2 visibility_periods_used secondary *d2 = GAIA DR2 duplicated_source secondary * value given only in download file

Table B1: KPP objects cross-matched with EB18_v2 (stub from download file)

The number of 4,217 newly found KPP objects seems even with the restriction to the angular separation of 60" rather modest compared to the >55,000 objects in the EB18 catalog, but the main reasons for this difference are obviously: • Aiming for most reliable GAIA DR2 parallaxes I selected only objects with <0.5% parallax error (means compared to EB18 more rigid to a factor of 10) • Cross-matching with the WDS catalog to eliminate all already known double stars • Calculating the distance between the components using the given GAIA DR2 data for the secondary instead of assuming the parallax for the secondary being ident with the parallax for the primary.

The remaining >1,000 KPP objects not covered by EB18 are to be explained as follows: • Multiples were not excluded but considered of special interest • Common proper motion was considered not relevant for assessing a pair as likely physical (see Knapp 2019

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 205

Counter-Check of Binaries Reported to be Detected in Gaia DR2 as well as an Equal Mass “Twin” Binary ...

on “True movement …”) so the KPP data set includes many objects with rather different proper motion values.

Side result: The EB18 catalog was designed to include only binary pairs by eliminating suspected multiples – this did not completely work out. 57 of the positively matched KPP objects refer to components of multiples with components given in the “Comp” column. Additionally there are 16 objects overlapping with one component indicating a corresponding number of multiples with an additional component outside the KPP objects 60” search radius. Finally there are 551 objects with GAIA DR1 field “duplicated_source” = 1 for at least one component which means that these components are potentially doubles themselves. In total this means a significant contamination of the EB18 catalog with multiples even if a part of these multiples might not be physical but just optical. Why the authors of EB18 did not exclude objects with “duplicated_source” = 1 remains unclear.

Appendix C Effects of presenting data in graphs

Presenting results with estimated values in graphs has some caveats. The very same EB19 data set with Star- Horse mass50 can be presented in graphs with different bin size allowing for different conclusions showing that this kind of data presentation is close to manipulating results: Just another experiment with single digit rounded mass50 values as substitute for “estimated” masses shows

Graph C1 to C3: Presenting identical data with different bin sizes

that selecting bin size combined with crude estimated values might result in undesired distortions delivering quite different conclusions: Same data as above but with single digit rounded EB19 StarHorse mass50 values with a bin size of 0.1: Com- pared with graph C1 there is suddenly a peak at q = 0.5.

Graphs C4 and C5: Presenting ident but rounded data with different bin sizes

The ident result in bins of 0.01: The equal mass spike is compared to graph 3 with 14.76% suddenly truly significant enough to draw conclusions for an excess in “twin” pairs. I certainly do not want to impute to the EB19 authors the intention to tamper with their data to get a desired result but I wanted to demonstrate that limited precision of data (by rounding or estimating) and selecting bin size for presentation of the ratio of such data in graphs can lead to unexpected distortions of the results.

Vol. 16 No. 2 April 1, 2020 Journal of Double Star Observations Page 206

Journal of Double Star Observations The Journal of Double Star Observations (JDSO) April 1, 2020 publishes articles on any and all aspects of astronomy in- Volume 16, Number 2 volving double and binary stars. The JDSO is especially interested in observations made by amateur astronomers. Editors Submitted articles announcing measurements, discover- R. Kent Clark ies, or conclusions about double or binary stars may un- Russ Genet dergo a peer review. This means that a paper submitted Richard Harshaw by an amateur astronomer will be reviewed by other ama- Jo Johnson teur astronomers doing similar work. Rod Mollise

Assistant Editors Submitted manuscripts must be original, unpublished Vera Wallen material and written in English. They should contain an abstract and a short description or biography (2 or 3 sen- Student Assistant Editor tences) of the author(s). For more information about for- Eric Weise mat of submitted articles, please see our web site at http://www.jdso.org Advisory Editors Brian D. Mason Submissions should be made electronically via e-mail William I. Hartkopf to [email protected] or to [email protected]. Articles should be attached to the email in Microsoft Web Master Word, Word Perfect, Open Office, or text format. All Michael Boleman images should be in jpg or fits format.

The Journal of Double Star Observations (ISSN 2572-4436) is an electronic journal published quarterly. Copies can be freely downloaded from http://www.jdso.org.

No part of this issue may be sold or used in commercial products without written permis- sion of the Journal of Double Star Observa- tions.

Questions, comments, or submissions may be directed to [email protected] or to [email protected]