Vol. 9 No. 3 July 1, 2013 Journal of Double Star Observations Page Journal of Double Star Observations

VOLUME 9 NUMBER 3 July 1, 2013

Inside this issue:

A New Common Proper Motion Double Star in Sagittarius 173 Abdul Ahad Measurement of Double Stars Using Webcams 2011 and 2012 176 Allen S. Malsbury, P.E UCAC2 42913552 a Double Star Discovered During an Asteroidal Occultation 183 Ricard Casas, Jorge Juan, Ramon Naves, Carles Perelló, Joan Rovira, Antoni Selva, Carles Schnabel Double Star Measurements Using A Small Refractor 189 Marc Oliver Maiwald Lucky Imaging Astrometry of 59 Andromedae Bobby Johnson, Sophia Bylsma, Cameron Arnet, Everett Heath, Jason Olsen, Anna Zhang, 195 Kaela Yancosek, Russell Genet, Jolyon Johnson, Joe Richards Useful Lists of Double Stars 203 Joseph M. Carro Visual Astrometry of 35 Cassiopeiae Joseph Carro, Alyssa Adams, Garrett Moore, Triston Perez, Sarah Thomas, Oksana Moscoso, Krystyn 207 Michaud, Joseph Richards, Jolyon Johnson, Russell Genet Observing 75 Draco with a Manual Dobsonian Telescope 210 Joseph Richards, Megan Calabrese, Alexandria Calabrese, Mckenzie Calabrese The Visual Triple Star ADS 16185 - STF2934 214 Henry Zirm POU 5641 (WDS 22077+2521). A Binary Composed of a Red dwarf and a White Dwarf 221 F. M. Rica

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A New Common Proper Motion Double Star in Sagittarius

Abdul Ahad

Bedfordshire United Kingdom

[email protected]

Abstract: In this paper I report a new visual binary star in the constellation Sagittarius that is not in the current edition of the WDS catalog, the components of which share a common proper motion. On observed photometric characteristics, estimation of distance, and other assumptions, it has not been possible to rule out a possible physical association between the two stars.

Introduction I had first noticed this pair as a CPM double star back in May 2012, while imaging ‘fast-moving’ double stars from the WDS catalog in the general vicinity in the neighboring constellation of Capricornus. The pri- mary has the designation HD 186751, is of V mag +9.7 and resides at ICRS: 19 46 50.7 -15 55 41 (2000.0). The secondary is of V mag +10.4, 25.2 arcseconds away from the primary. Offering a spectacular sight in small telescopes, this pair is located in an exciting region of the sky not far from the summer Milky Way in northeastern Sagittarius (Figure 1). A close-up FITS image was obtained in the J-band (taken at a wavelength of 1.24 µm) from the Two Mi- Figure 1: Location of the proposed new double star cron All-Sky Survey [1] for epoch 1999-06-07, as shown in Figure 2. From this image (which is of an adequately high resolution of 0.9 arcseconds per pixel) Proper Motion and Distance Calibration the following positional measures were found: From the UCAC3 Catalog [2], we find the two stars share similar proper motions in both RA and Dec, in Position Angle (θ): 352.0o (Epoch 1999.4326) both magnitude and in sign, Table 1. The pair as a whole has a total proper motion of: Separation (ρ): 25.24" (Epoch 1999.4326) 25.522 2.0 25.5 22  4.0  25.7 mas/yr. 2

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A New Common Proper Motion Double Star in Sagittarius

Figure 2: Image from 2MASS, taken in the J-band.

and we know the Sun is classified as a G2V star on the From the 2MASS catalog, we find the J and K-band H-R diagram. We also know that a G2V star typically magnitudes for the two components in this Sagittarius shines at an absolute magnitude of +4.8, and applying double star given in Table 2. From these we compute the distance modulus formula to the primary’s apparent color indices of (J – K) = +0.32 for the primary and (J – visual magnitude of 9.7, yields a distance to the primary K) = +0.40 for the secondary component. of about 300 light-years. This distance is consistent with A 2MASS color index (J – K) for the primary star of the total proper motion of 25.7 mas/year for the pair, +0.32 suggests it to be a ‘Sun-like’ star with a spectral from the broad relationships between the observed class near a G2. proper motion and likely distance I have referenced in The absolute magnitude of the Sun, for example, has previous papers. This is then sufficient evidence to sup- been calibrated in various photometric bands where its pose the primary is likely to be similar to a G2V star, (J – K) color index is approximately equated to +0.36, much like our own Sun.

Table 1: Proper motion of the components Table 2: J and K magnitudes of the components Proper Motion Proper Motion J-magnitude K-magnitude in RA in Dec A-component +25.5 mas/yr +2.0 mas/yr A-component +8.376 +8.058

B-component +25.5 mas/yr +4.0 mas/yr B-component +9.010 +8.608

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A New Common Proper Motion Double Star in Sagittarius

The secondary’s color index of +0.40 suggests it to ter of the Milky Way galaxy. The observed photometric be a much cooler and comparatively less luminous star properties of each star and a calibrated distance of circa compared to the primary, and of spectral class K on the 300 light-years for the pair give a strong indication that H-R diagram. they might be gravitationally linked. Considering also Differencing the apparent magnitudes of the two the visual spectacle that would be afforded to telescopic stars, we find a Δm of 0.68 that is consistent with the observers in potential occultations by the Moon, it is observed color difference between the two component recommended that this pair be included in the WDS stars and with their respective spectral classifications. catalog as an exciting new visual double star. This further suggests they are both shining from a simi- lar (if not the same) distance, estimated to be 300 light- References years away. 1. The Two Micron All-Sky Catalog of Point Sources (Cutri, et al., 2003) Lunar Occultations Positioned less than 6o north of the ecliptic line in 2. UCAC3 Catalog (Zacharias, et al., 2009) the sky means this pair can get occulted by the Moon in its monthly circuits of the sky, and such occultations would be repeated over a cycle of about 19 years. Visi-  bility will be restricted to observers located in the south- ern hemisphere of Earth, however, due to the specific position of this pair and orientation of the lunar orbit relative to the Earth’s equatorial plane. According to simulations carried out using the Stellarium planetarium software, in the present cycle, the Moon will pass in front of the two stars in succession as seen from Cape Town, South Africa on the night of 24th-25th June 2013 and again on 18th August 2013. Similar occultations may be observed from Sydney, Australia on 28th-29th May 2013 and again on 22nd July 2013. Conclusions Given their virtually identical common proper mo- tions, the two stars are most likely drifting in the same direction in 3D space in their travels relative to the cen-

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Measurement of Double Stars Using Webcams 2011 and 2012

Allen S. Malsbury, P.E

Parsippany, New Jersey, USA

[email protected]

Abstract: A description is given of the equipment and software used to image and measure 97 different double star systems. A summary of these measurements is provided.

Fusion were modified for astronomical imaging use. Introduction Their lenses were removed and they were fitted with Measuring double stars using webcams has been 1¼” nose piece adaptors. Double stars as faint as mag- demonstrated and well documented by others. The nitude 8 could be imaged using these cameras when equipment and software necessary to measure double combined with a fast 6" f/5.6 Newtonian with no Bar- star separations and position angles were assembled low lens. At higher f-numbers, f/12, magnitude 7 stars using prior Journal of Double Star Observations or brighter could be captured. Above f/12, stars of (JDSO) papers as a guide. Following is a description of magnitude 6.5 or brighter could be imaged. Despite the the equipment and software used to image and measure limitations of these cameras, a significant number of 97 different double star systems. A total of 224 meas- double stars were imaged using the Neximage, Toucam, urements were completed during 2011 and 2012. and Fusion cameras. Later these webcam cameras were Equipment and Software Used replaced with a more sensitive Imaging Source camera. Good results were achieved using the Imaging Source CCD Cameras camera with the ICX618 CCD monochrome chip. Mag- Four different CCD cameras were used to collect nitude 8 stars were imaged at relatively high f-numbers the data presented here. All of the cameras used could using this monochrome camera. The Imaging Source be considered “webcams”, having a USB computer in- camera was combined with a small homemade 4” f/29 terface and live view capability. Video data were cap- Schiefspiegler telescope to provide acceptable images tured and saved in an Audio Video Interleaved (AVI) even with separations as close a 2 arc-seconds. format. Frame rates used varied, depending on the sub- Observing List ject star’s magnitude, f-number of the optical system, An observing list matching the limitations of the and sensitivity of the camera being used. Typical frame webcam cameras was prepared. Skytools 3 was used to rates were between 5 and 60 frames per second. prepare a “webcam-able” list. A search of the Sky- Initially, imaging was done using one of three low tools’ database produced a list containing more than cost cameras. These were the Celestron Neximage, 150 double stars. All of these became candidates for Phillips Toucam, and Logitech Fusion webcams. The webcam imaging. To date, however, only 97 have been stock Neximage camera fit into a standard 1¼” focuser imaged and measured. The webcam-able list included and required no modification. Both the Toucam and

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Measurement of Double Stars Using Webcams 2011 and 2012

only those double stars with both major and minor stars recorded with the telescope mount stopped and not brighter than magnitude 8. In addition, separations of 3 tracking. The subject star “drifted” across the CCD arc-seconds or greater were selected for the initial ob- chip of the camera, documenting a different star loca- servation, given typical seeing conditions in New Jer- tion in each consecutive frame of the drift AVI file, sey. It should be noted that many of the tighter doubles essentially recording the rotation of the earth about its with faint minor stars could not be imaged until the own axis. more sensitive Imaging Source camera was acquired. Although Reduc can be calibrated for any tele- Laptop Computer scope, Barlow lens, and camera combination using a A laptop computer was used to control each cam- calibration double star, this option was not used. In- era and to capture the AVI files via a USB interface. In stead, image scales were determined from star drift addition, the laptop was used to control an Orion Sirius data using LiMovie as explained below. The image German equatorial mount (GEM) using Skytools with scale for each optical system was input directly into Realtime, ASCOM, and EMOD plugins. Reduc once determined using LiMovie. LiMovie – Image Scale Estimation Portable Mass Storage LiMovie is freeware that was written to assist in An external hard drive was used to store the AVI the measurement of occultations. It was used to deter- files as they were recorded. The older laptop used for mine the image scale of each telescope, camera, and imaging had a small internal hard drive that could not Barlow lens combination using drift AVI files. Li- support one night’s imaging. Movie tracked the subject star’s drift, frame by frame, Telescope and Barlow Lenses reporting its pixel position in x and y coordinates for Three different telescopes were used during 2011 each frame. A comma delimited file containing these and 2012. Double stars were imaged using a home- frame-by-frame pixel positions was exported from Li- made 6” f/5.6 Newtonian during 2011. Two different Movie. The comma delimited file was opened using Barlow lenses, 2x and 3x, were used when needed to Excel for analysis. improve the image scale of this fast Newtonian. A 6” The first and last star locations were used to deter- f/12 Newtonian was constructed by the end of 2011. mine the total number of pixels the star drifted. The Later, in May of 2012 the construction of a 4” f/29 frame rate of the AVI and the total number of frames Schiefspiegler was completed. It was used for imaging was used to determine the total elapsed time of the during the second half of 2012. trial. Using the Declination of the subject star, the im- German Equatorial Mount age scale of the combined camera, Barlow lens, and A medium duty Orion Sirius German Equatorial telescope system was calculated as follows: Mount (GEM) was used for all data collection. The GEM was controlled by a laptop computer as noted Image Scale = (15*t*Cosine(Dec))/Pix above. in arc-sec/pixel, where: Software t = Total elapsed time in Seconds AMCap and IC Capture – AVI File Capture Software DEC = Declination in degrees The Imaging Source camera was supplied with Pix = Length of Star Trail in pixels capture software, IC Capture. AMCap was used with the other three webcam cameras. Skytools 3 – Webcam List Creation, Logging and GEM con- Registax – Imaging Stacking and Enhancement trol Registax was used for stacking the individual Skytools 3 is multifunctional software for observa- frames of the AVI file recorded with the GEM track- tion planning, and logging. Skytools was also used to ing. Stacking is a common method used to improve the control the GEM mount during each imaging session. signal to noise ratio, thus producing an improved im- Reduc – Post Processing Software age. Registax has an image quality assessment routine Reduc was used to determine the position angle that selects the good frames captured between periods and separation of each double star imaged. Reduc per- of bad seeing. Registax aligned and stacked each good formed a drift analysis using the “drift” AVI file to de- frame, producing a final jpg image of the double star termine the camera orientation. Each “drift” AVI was system. Registax was also used to stack drift AVI files,

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Measurement of Double Stars Using Webcams 2011 and 2012

producing an artificial star trail image. create an image of the double star in jpeg format. Reg- The star trails point westward. Reduc uses this fact istax was also used to stack one of the drift AVI files, during its Drift analysis of each artificial star trial im- producing an artificial star trail image. The star trail age. In addition, the star trail image was used to deter- image was saved in both bitmap and jpeg formats. mine the double star’s correct orientation as it was cop- The jpeg version of the star trial image was used to ied onto the record-plate. See an example of a record- rotate and orient the final double star jpeg image on the plate in Appendix B. record-plate, as noted above. The bitmap version of VirtualDub – AVI Editing and Conversion the star trail image was used by Reduc to establish the On occasion, captured AVI files required some image angle for the double star being analyzed. The editing. When needed, VirtualDub was used to shorten two AVI files recorded with the GEM tracking were and/or copy AVI files. AVI files recorded by the IC then separated into individual bitmap images using the Capture software were not compatible with the Reduc AVI-to-bitmap conversion routine within Reduc. software. However if each file was copied and resaved These individual bitmap images were processed by Re- using VirtualDub, Reduc would accept and process the duc to determine each separation and position angle. copied version without complaint. The measured separations, position angles, and all Paint.net – Imaging Editing and Plate Preparation other relevant information were recorded in an Excel Paint.net was used to edit and enhance the quality file. of the double stars imaged. Techniques similar to those Final Data Records employed to enhance deep sky object images were used Table 1 (following page) provides a summary of to improve each double star image. Enhanced double the observations made during 2011 and 2012. Appen- star images were copied into a record-plate to perma- dix A shows a printer friendly positive, as well as a nently document the recorded image. In addition, the negative record-plate of one of the observations. These measured separation and position angle and other infor- plates were made as a record for each observation. mation such as its Right of Ascension (RA) and Decli- nation (Dec), the date recorded, and equipment used was added to the record-plate. See an example of a re- cord-plate in Appendix A. Double Star Observation and Imaging Each double star observation included recording a total of four AVI files. Two were captured with the GEM tracking at a sidereal rate, and two “drift” AVI files were recorded with the GEM stopped and not tracking. Frame rates used varied depending on the subject star’s magnitude, f-number of the optical sys- tem, and sensitivity of the camera being used. Typical frame rates were between 5 and 60 frames per second. As each double star was imaged, a log of each ob- servation was recorded using Skytools’ logging feature. These logs included the seeing and transparency condi- tions at the time of the observation, the date, equip- ment, Barlow lens employed (if any), the direction of the drift, and general description of the relative magni- tudes and separation of the major and minor stars. Post Processing Post processing of the four AVI files recorded for each double star was completed as follows: One of the two AVI files recorded with the GEM tracking was stacked and enhanced using Registax to

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Measurement of Double Stars Using Webcams 2011 and 2012

Table 1: Summary of Double Star Observations, 2011 and 2012

RA+DEC Discoverer Sep PA Date N Remarks 00026+6606 STF3053AB 15.20 71.960 2011.710 2 HR9094 00491+5749 STF 60AB 13.28 322.15 2011.710 2 Achird 01001+4443 STF 79 7.75 195.22 2011.857 4 HR 283 01057+2128 STF 88AB 29.66 160.48 2011.767 2 Psi 1 Psc 01137+0735 STF 100AB 23.00 63.26 2011.767 2 Zeta Psc 01496-1041 ENG 8 184.52 250.73 2011.767 2 Chi Cet 01536+1918 STF 180AB 7.41 0.11 2011.997 2 Mesarthim 01562+3715 STFA 4AB 203.15 297.48 2011.767 2 56 And 01580+2336 H 5 12AB 37.40 47.47 2011.767 2 Lambda Ari 02039+4220 STF 205A-BC 10.07 64.67 2011.767 2 Almaak 02128-0224 STF 231AB 16.80 234.12 2011.767 2 66 Cet 02358+3441 AG 304 142.59 16.82 2011.767 2 15 Tri 02507+5554 STF 307AB 29.23 299.84 2012.494 4 Miram 03009+5221 STF 331 12.04 84.95 2012.022 6 HR890 03543-0257 STF 470AB 6.91 351.13 2011.997 2 32 Eri 04226+2538 STF 528 19.22 24.29 2012.494 4 Chi Tau 04254+2218 STF 541AB 344.48 173.94 2011.997 2 Kappa 1 Tau 04287+1552 STFA 10 341.19 347.18 2011.997 2 Theta 2 Tau 04306+1612 LDS2246 253.95 130.42 2011.997 2 HR 1427 04320+5355 STF 550AB 10.60 308.02 2012.991 2 1 Cam 04393+1555 STFA 11 444.07 194.39 2011.997 2 Sigma 2 Tau 04422+2257 S 455Aa-B 63.77 213.46 2012.494 4 Tau Tau 05061+5858 STFA 13AB 180.16 10.34 2011.997 2 11 Cam 05228+0333 STF 696 31.99 29.72 2011.997 2 23 Ori 05322+1703 STF 730 9.53 139.42 2011.997 2 HR 1847 05354-0525 STFA 16AB 51.99 92.84 2012.170 2 Theta 2 Ori 05354-0555 STF 752AB 11.61 140.71 2012.170 2 Nair al Saif 06090+0230 STF 855AB 28.98 113.57 2012.170 2 HR 2174 06116+4843 STF 845 7.48 357.78 2011.997 2 41 Aur 06238+0436 STF 900AB 12.22 28.42 2012.170 2 Epsilon Mon 10084+1158 STFB 6AB 175.21 307.05 2012.381 2 Regulus 10433+0445 STF1466AB 6.73 239.65 2012.381 2 35 Sex 10556+2445 STF1487 6.71 112.49 2012.381 2 54 Leo 12021+4303 FOR 1AB 273.55 61.98 2012.381 2 67 UMa

Table 1 continues on next page.

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Measurement of Double Stars Using Webcams 2011 and 2012

Table 1 (continued): Summary of Double Star Observations, 2011 and 2012

RA+DEC Discoverer Sep PA Date N Remarks 12351+1823 STF1657 20.05 270.39 2012.381 2 24 Com 12492+8325 STF1694AB 20.93 323.85 2011.777 2 HR 4893 12560+3819 STF1692 19.20 229.40 2012.381 2 Cor CAROLI 13101+3830 STFA 24AB 275.61 296.28 2012.381 2 17 CVn 14407+1625 STF1864AB 95.77 185.35 2012.498 4 Pi 1 Boo 14450+2704 STF1877AB 3.42 340.87 2012.575 2 Izar 14514+1906 STF1888AB 6.65 301.19 2012.575 2 Xi Boo 15141+3147 STT 292 118.15 157.27 2011.641 2 HR5674 15156+3319 STFA 27 103.88 77.69 2012.381 2 Delta Boo 15245+3723 STFA 28a-BC 107.64 170.75 2011.639 2 Alkalurops 15387-0847 STF1962 11.79 190.52 2011.639 2 HR5816 15394+3638 STF1965 305.99 6.45 2011.625 2 Zeta 2 CrB 16081+1703 STF2010AB 26.79 13.32 2011.641 2 Mirfak 16081+1703 STF2010AB 27.01 14.14 2011.64 2 Kappa Her 16147+3352 STF2032AB 7.25 237.87 2011.625 2 Sigma CrB 16224+3348 STFA 29AB 354.69 164.20 2011.63 2 Nu 1 CrB 16362+5255 STFA 30AC 89.78 193.94 2011.641 2 17 Dra 16406+0413 STFA 31Aa-B 229.25 69.38 2011.625 2 37 Her 17037+1336 STFA 33AB 305.59 116.57 2011.625 2 HR6341 17053+5428 STF2130AB 2.50 6.85 2011.641 2 Mu Dra 17146+1423 STF2140Aa-B 5.76 99.98 2011.639 2 Rasalgethi 17150+2450 STF3127Aa-B 12.52 288.48 2012.059 5 Sarin 17237+3709 STF2161Aa-B 4.21 320.37 2011.639 2 Rho Her 17322+5511 STFA 35 61.99 310.44 2011.611 2 Kuma 17419+7209 STF2241AB 29.95 16.45 2011.611 2 Dsiban 17419+7209 STF2241AB 29.98 15.84 2011.665 4 Psi 1 Dra 18002+8000 STF2308AB 19.27 232.11 2011.767 2 41 Dra 18015+2136 STF2264 6.54 259.34 2011.640 3 95 Her 18055+0230 STF2272AB 6.56 129.42 2011.705 6 70 Oph 18078+2606 STF2280Aa-B 13.80 179.93 2011.640 3 100 Her 18443+3940 STFA 37BC 210.87 171.82 2011.607 4 Epsilon 1 Lyr 18455+0530 STF2375Aa-Bb 2.91 114.85 2012.805 2 HR7048 18465-0058 STF2379Aa-B 12.64 122.31 2011.611 2 5 Aql 18501+3322 STFA 39AB 45.44 148.72 2011.641 2 Sheliak 18512+5923 STF2420AB 36.38 318.01 2011.611 2 Omicron Dra

Table 1 concludes on next page.

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Measurement of Double Stars Using Webcams 2011 and 2012

Table 1(conclusion): Summary of Double Star Observations, 2011 and 2012

RA+DEC Discoverer Sep PA Date N Remarks 18562+0412 STF2417AB 22.43 103.97 2011.611 2 Theta 1 Ser 19050-0402 SHJ 286 39.35 209.63 2011.611 2 15 Aql 19121+4951 STF2486AB 7.29 206.14 2012.190 4 HR7294 19153+1505 STTA178 89.13 267.03 2011.611 2 HR7300 19287+2440 STFA 42 424.37 28.33 2011.611 2 Alpha Vul 19307+2758 STFA 43Aa-B 34.81 54.78 2011.611 2 Aberio 19418+5032 STFA 46Aa-B 41.50 127.76 2012.190 4 16 Cyg 19546-0814 STF2594 169.80 36.95 2011.767 2 57 Aql 20136+4644 STFA 50Aa-C 60.13 164.13 2011.665 4 31 Cyg 20145+3648 ENG 72AB 213.95 158.91 2011.576 2 29 Cyg 20210-1447 STFA 52Aa-Bb 208.83 266.85 2011.767 2 Dabih 20299-1835 SHJ 324 22.49 237.25 2011.767 2 Omicron Cap 20410+3218 STF2716Aa-B 3.54 51.63 2012.731 2 49 Cyg 20467+1607 STF2727 9.54 266.40 2011.751 4 Gamma 2 Del 20585+5028 STF2741AB 1.96 30.43 2012.731 2 HR 8040 21069+3845 STF2758AB 31.91 150.63 2012.036 6 61 Cyg 21287+7034 STF2806Aa-B 13.88 248.93 2011.641 2 Alfirk 21434+3817 S 799AB 148.51 59.65 2011.576 2 79 Cyg 21520+5548 STF2840AB 17.77 196.14 2011.576 2 HR8357 22038+6438 STF2863Aa-B 8.18 279.65 2011.579 2 Alkurhah 22038+6438 STF2863Aa-B 8.51 273.34 2011.71 2 HD 209790 22288-0001 STF2909 2.16 160.03 2012.89 2 Zeta 1 Aqr 22359+3938 STF2922Aa-B 22.53 184.85 2012.24 4 8 Lac 23052-0742 STFA 59AB-C 257.62 149.24 2012.00 2 83 Aqr 23191-1328 STF2998Aa-B 12.57 349.16 2012.89 2 94 Aqr 23248+6217 H 6 24AB 96.13 225.67 2011.71 2 4 Cas 23460-1841 H 2 24 7.45 131.53 2012.89 2 107 Aqr 23590+5545 STF3049AB 3.48 327.93 2011.71 1 HD 224572

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Measurement of Double Stars Using Webcams 2011 and 2012

Appendix A

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UCAC2 42913552, a Double Star Discovered During an Asteroidal Occultation

Ricard Casasa,b,c Bellaterra (Catalonia, Spain), [email protected]

Jorge Juan Hostalets de Pierola (Catalonia, Spain), [email protected]

Ramon Navesd Cabrils (Catalonia, Spain), [email protected]

Carles Perellób Sabadell (Catalonia, Spain)

Joan Rovirab Moià (Catalonia, Spain)

Antoni Selvab Sabadell (Catalonia, Spain)

Carles Schnabelb,c Sant Esteve Sesrovires (Catalonia, Spain), [email protected]

a Institut de Ciències de l’Espai (IEEC-CSIC) b Agrupació Astronòmica de Sabadell c International Occultation Timing Association, European Section d Agrupació Astronòmica de Barcelona - ASTER

Abstract: The occultation of the star UCAC2 42913552 by the asteroid 388 Charybdis on De- cember 3rd, 2012 has shown the duplicity of the star. Six observations carried out from Catalo- nia, Spain enable the determination of the parameters of this double star. A separation of 28.6 ± 0.6 milliarcseconds (mas) and a position angle (PA) of 110.2 ± 3.6 degrees has been calculated. From the steps in the light curve the estimated magnitudes without filter are 11.7 and 12.0. We suggest that this pair be included in the WDS catalog.

55’ 48.76” (J2000.0). Introduction The magnitude of the asteroid 388 Charybdis in the On December 3, 2012 the asteroid 388 Charybdis moment of the occultation was 13.4. This value has occulted the star UCAC2 42913552. This occultation, been obtained in the ephemeris web page of the Minor predicted by Steve Preston (Figure 1), was observable Planet Center (http://www.minorplanetcenter.net). from northern Spain. UCAC2 42913552 is a 11.3 magnitude star with the Observations equatorial coordinates RA 6h 50m 29.57s, Dec. +31º Six stations observed this occultation with positive

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UCAC2 42913552 a Double Star Discovered During an Asteroidal Occultation

Figure 1. Prediction of the occultation of the star UCAC2 42913552 by the asteroid 388 Charybdis on December 3rd, 2012 predicted by Steve Preston (http://www.asteroidoccultation.com/)

results. Table 1 gives the geographical coordinates and While the observation of station #1 had a poor instrumentation used. SNR, the other five stations obtained good light curves of the event, shown in Figures 2–6. (Continued on page 187)

Table 1. Geographical coordinates and equipment of each station

Longitude, Integration # Station Team Latitude & Telescope Equipment used Altitude 2º 07’ 14.7” E Schmidt- TV Camera 1 R. Casas 41º 32’ 22.1” N Cassegrain Mintron 12V6H-EX + KIWI 0.24 s 165 m 20 cm f/10 inserter time 1º 45' 55" E TV Camera Newton 2 J. Juan 41º 32’ 21” N Watec 120N+ + KIWI in- 0.04 s 40.6 cm 423 m serter time 2º 23’ 07.6” E Schmidt- CCD Camera 3 R. Naves 41º 31’ 11.3” N Cassegrain ST8-MXE + NTP + N/A 114 m 30 cm f/10 Driftscan method 2º 05’ 24.8” E TV Camera C. Perelló – Newton 4 41º 33’ 00.2” N Mintron 12V6H-EX + KIWI 0.04 s A. Selva 50 cm f/4 224 m inserter time 2º 05’ 45.1” E Newton Mintron 12V6H-EX + KIWI 5 J. Rovira 41º 49’ 05.4” N 0.16 s 20 cm f/5 inserter time 827 m 1º 52’ 25.7” E TV Camera Newton 6 C. Schnabel 41º 29’ 41.5” N Mintron 12V6H-EX + KIWI 0.08 s 40 cm f/4 180 m inserter time

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UCAC2 42913552 a Double Star Discovered During an Asteroidal Occultation

Figure 2. Light curve obtained by J. Juan, station #2, using the software Tangra written by H. Pavlov (http:// www.hristopavlov.net/Tangra/Tangra.html).

Figure 3. Light curve obtained by R. Naves, station #3, using the software Winscan written by C. Flohr (http:// www.driftscan.com/).

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UCAC2 42913552 a Double Star Discovered During an Asteroidal Occultation

Figure 4. Light curve obtained by Perelló-Selva, station #4, using the software Limovie written by K. Miyashita (http://www005.upp.so-net.ne.jp/k_miyash/occ02/limovie.html).

Figure 5. Light curve obtained by J. Rovira, station #5, using Tangra software.

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UCAC2 42913552 a Double Star Discovered During an Asteroidal Occultation

Figure 6. Light curve obtained by C. Schnabel, station #6, using Limovie software for the analysis.

(Continued from page 184) 12.0 ± 0.1 and 11.7 ± 0.1 for the second one. These magnitudes are an approximation, since there were no Data Analysis photometric filters placed in front of the detectors. Four timings have been registered for each station. The figures clearly show the presence of two stages As the secondary star (fainter) was the first one to be in the ingress and in the egress. The two stages are a occulted, we label it as D2 (Disappearance of 2) the first characteristic clear signal of a double star system. Based timing, D1 (Disappearance of 1) the second one, R2 on the nominal magnitude of the system (double star (Reappearance of 2) the third one and R1 (Reappearance plus asteroid), 11.2, and the signal measured in these of 1) the last one. These timings are listed in Table 2. observations, we estimate the magnitude for each sta- All timings obtained with TV-cameras (except sta- tion, obtaining a magnitude for the first occulted star of tion #3) have been corrected following the values ob-

Table 2. Timings of the occultation. D1 and R1 are the disappearance and the reappearance of the brightness compo- nent of the double star, while D2 and R2 are, respectively, the disappearance and the reappearance of the secondary component.

# D2 D1 R2 R1

1 00:11:02.34 ± 0.82 00:11:05.91 ± 0.51 00:11:13.10 ± 0.83 00:11:17.79 ± 0.55

2 00:11:04.20 ± 0.53 00:11:08.35 ± 0.28 00:11:15.77 ± 0.40 00:11:20.12 ± 0.38

3 00:10:59.75 ± 0.10 00:11:04.25 ± 0.10 00:11:11.75 ± 0.10 00:11:11.75 ± 0.10

4 00:11:01.74 ± 0.45 00:11:05:87 ± 0.28 00:11:13.34 ± 0.49 00:11:17.70 ± 0.39

5 00:11:01.35 ± 0.43 00:11:05.71 ± 0.26 00:11:12.69 ± 0.54 00:11:16.81 ± 0.55

6 00:11:03.21 ± 0.59 00:11:07.82 ± 0.55 00:11:15.19 ± 0.66 00:11:19.42 ± 0.52

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UCAC2 42913552 a Double Star Discovered During an Asteroidal Occultation

tained by Gerhard Dangl (http://www.dangl.at/ausruest/ Table 3. Parameters of the double star vid_tim/vid_tim1.htm). UCAC2 42913552 Using the software Occult 4.1.0 from David Herald (http://www.lunar-occultations.com/iota/occult4.htm) Distance (mas) 28.6 ± 0.6 we fit the shape of the asteroid to an ellipse, obtaining a PA (degrees) 110.2 ± 3.6 result of 150.0 ± 3.6 km × 118.0 ± 0.9 km, see Figure 7. A separation and position angle of the occulted double star were also obtained and the values are listed in table 3. Conclusions The casual occultation caused by an asteroid of the star UCAC2 42913552 revealed its duplicity. The fact that a relatively large number of observers registered it has allowed us to determine the parameters of this bi- nary system.

Figure 7. Plot and fit obtained with Occult 4.1.0 (D. Herald)

Vol. 9 No. 3 July 1, 2013 Journal of Double Star Observations Page 189

Double Star Measurements Using A Small Refractor

Marc Oliver Maiwald

Witten, Germany [email protected]

Abstract: On the following pages, I present measurements of stars made from 2010 to 2012 with a 6 inch folded refractor.

The Instrument used for these measurements is a In most cases the position angle of the camera was folded refractor of the type known as “Schaer – Refrac- calibrated with drifts of the double star actually meas- tor” or “réfracto – réflecteur”. It is equipped with an air ured. Exceptions were made if two double stars were – spaced achromatic doublet made by Lichtenknecker close neighbours in the sky. In a few cases a nearby star Optics, which has a free aperture of 150mm and and a was used for the drift calibration, especially when a focal length of 3000mm. The secondary spectrum was binary was too faint for good drift exposures. Normally eliminated by a yellow – green filter (No 11), which 10 drifts were taken for every star. also removes atmospheric dispersion. In most cases 25 to 100, and sometimes even 200, The image scale at the prime focus is 0,384”/pixel. AVI files were taken for each star at one observing ses- Double Stars with separations < 1,5” can be resolved, sion. The AVI files were processed with Registax. The but are difficult to measure with acceptable accuracy. resulting pictures were measured with Reduc and pic- For observation of these doubles – as for many observa- tures of lower quality were rejected. In Table 1 under tions of wider pairs - different optical setups were tried: “No” the number of pictures actually used for the final With a Barlow lens and an image scale of 0,232”/pixel, value is listed. with Telekonverters and image scales of 0,19876”/pixel The table begins on the next page. and 0,189”/pixel. Calibration of the image scale was done with calibration stars. The plate scale of the in- strument is nearly constant, due to the thermal stability of long – focus refractors. The camera used for most of the observations is a DMK 21 bw - camera with 480 x 640 pixels and a pixel size of 5,6 micron, manufactured by “The Imaging Source”. It is more comfortable to use and has less elec- tronic noise than webcams. It was used at the highest “gain” setting and typical exposure times ranged from 1/60s or even shorter for bright pairs down to 1/5 or 1/4s for stars of 8th magnitude.

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Double Star Measurements Using A Small Refractor

Name RA & De PA Sep Date No Notes STF 3053AB 00026+6606 70.4 15.13 2012.827 36 STF 59 00480+5127 147.9 2.24 2012.826 38 STF 60AB 00491+5749 322 14.06 2010.716 19 η Cas STF 60AB 00491+5749 322.8 13 2010.724 31 η Cas STF 60AB 00491+5749 323.2 13.06 2011.877 31 η Cas STF 60AB 00491+5749 323 13.21 2012.766 34 η Cas STF 73AB 00550+2338 326.5 1.13 2012.851 82 36 And H 3 23AC 01201+5814 230.9 134 2012.829 37 φ Cas S 397 01211+6439 341.9 57.19 2012.895 19 35 Cas STF 262AB 02291+6724 227.9 2.71 2010.784 18 ι Cas STF 262AB 02291+6724 229.3 2.9 2011.877 34 ι Cas STF 262AB 02291+6724 230.2 2.75 2012.810 42 ι Cas STF 262AC 02291+6724 113.3 7.39 2010.784 24 ι Cas STF 262AC 02291+6724 115.6 7.16 2012.810 39 ι Cas STF 299 02433+0314 298.4 2.08 2012.969 33 γ Ceti STF 948AB 06462+5927 69 1.87 2011.220 75 12 Lyn STF 948AB 06462+5927 69 1.85 2011.239 69 12 Lyn STF 948AB 06462+5927 68.9 1.88 2012.202 73 12 Lyn STF 948AC 06462+5927 308.8 8.82 2011.220 77 12 Lyn STF 948AC 06462+5927 308.9 8.81 2011.239 85 12 Lyn STF 948AC 06462+5927 308.8 8.79 2012.202 51 12 Lyn STF 1110AB 07346+3153 57.8 4.43 2010.187 10 α Gem STF 1110AB 07346+3153 57.3 4.68 2010.261 10 α Gem STF 1110AB 07346+3153 57.3 4.67 2010.272 12 α Gem STF 1110AB 07346+3153 56.4 4.76 2010.278 17 α Gem STF 1110AB 07346+3153 56.8 4.74 2011.145 17 α Gem STF 1110AB 07346+3153 57.3 4.75 2011.167 85 α Gem STF 1110AB 07346+3153 56.7 4.77 2011.192 74 α Gem STF 1110AB 07346+3153 56.2 4.85 2012.170 63 α Gem STF 1196AB 08122+1739 38.8 0.92 2010.187 7 ζ Cnc STF 1196AB 08122+1739 37.6 1.08 2010.264 10 ζ Cnc STF 1196AB 08122+1739 38.3 1.03 2010.272 19 ζ Cnc STF 1196AB 08122+1739 38.7 0.91 2010.275 6 ζ Cnc STF 1196AB 08122+1739 36.9 0.94 2011.214 106 ζ Cnc STF 1196AB 08122+1739 37.7 1.05 2011.222 90 ζ Cnc STF 1196AB 08122+1739 32.4 1.04 2012.180 71 ζ Cnc STF 1196AC 08122+1739 66.8 6.35 2010.187 10 ζ Cnc STF 1196AC 08122+1739 67.7 6.4 2010.209 8 ζ Cnc STF 1196AC 08122+1739 65.8 6.67 2010.264 10 ζ Cnc STF 1196AC 08122+1739 66.5 6.63 2010.272 13 ζ Cnc STF 1196AC 08122+1739 66.5 6.54 2010.275 8 ζ Cnc STF 1196AC 08122+1739 65.7 6.65 2011.214 107 ζ Cnc STF 1196AC 08122+1739 65.3 6.65 2011.222 76 ζ Cnc STF 1196AC 08122+1739 65.8 6.91 2012.180 72 ζ Cnc STF 1306AB 09104+6708 349.5 4.19 2011.310 15 σ2 Uma STF 1306AB 09104+6708 349.9 4.33 2011.313 50 σ2 Uma

Table continues on next page.

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Double Star Measurements Using A Small Refractor

Name RA & De PA Sep Date No Notes STF 1306AB 09104+6708 349.6 4.41 2012.217 22 σ2 Uma STF 1333 09184+3522 49.6 1.92 2010.272 10 STF 1333 09184+3522 49.2 1.8 2010.278 16 STF 1333 09184+3522 48.9 1.89 2010.291 12 STF 1333 09184+3522 49.3 1.81 2011.170 24 STF 1333 09184+3522 49.6 1.92 2011.176 65 STF 1333 09184+3522 49.8 1.93 2011.236 54 STF 1333 09184+3522 50.2 1.8 2012.208 31 STF 1334AB 09188+3648 224.1 2.6 2010.272 8 38 Lyn STF 1334AB 09188+3648 224.8 2.59 2010.275 9 38 Lyn STF 1334AB 09188+3648 224.1 2.66 2010.278 18 38 Lyn STF 1334AB 09188+3648 224.6 2.74 2010.291 11 38 Lyn STF 1334AB 09188+3648 223 2.57 2011.170 46 38 Lyn STF 1334AB 09188+3648 223.9 2.64 2012.202 73 38 Lyn STF 1338AB 09219+3811 297.5 1.06 2010.291 17 STF 1338AB 09219+3811 301.4 0.9 2010.297 15 STF 1338AB 09219+3811 301.4 1.07 2011.225 153 STF 1338AB 09219+3811 306 0.93 2012.216 70 STF 1424AB 10200+1950 125 4.46 2010.190 12 γ Leo STF 1424AB 10200+1950 125.9 4.86 2010.264 8 γ Leo STF 1424AB 10200+1950 125.8 4.66 2011.217 136 γ Leo STF 1424AB 10200+1950 125.9 4.66 2011.241 141 γ Leo STF 1424AB 10200+1950 126.2 4.69 2012.208 80 γ Leo STF 1523AB 11182+3132 210.1 1.62 2010.321 26 ξ Uma STF 1523AB 11182+3132 211.1 1.5 2010.352 21 ξ Uma STF 1523AB 11182+3132 202.2 1.61 2011.263 111 ξ Uma STF 1523AB 11182+3132 202.5 1.7 2011.269 63 ξ Uma STF 1523AB 11182+3132 194.4 1.6 2012.284 98 ξ Uma STF 1670 12417-0127 22.4 1.5 2010.373 20 γ Vir STF 1670 12417-0127 24.6 1.57 2010.384 22 γ Vir STF 1670 12417-0127 18.9 1.74 2011.297 114 γ Vir STF 1670 12417-0127 18.9 1.66 2011.300 100 γ Vir STF 1670 12417-0127 19.4 1.74 2011.302 76 γ Vir STF 1670 12417-0127 13.9 1.8 2012.364 99 γ Vir STF 1670 12417-0127 14.3 1.8 2012.367 79 γ Vir STT 261 13120+3205 338.7 2.62 2011.329 23 STT 261 13120+3205 338.6 2.58 2011.332 18 STF 1768 13375+3618 98.3 1.76 2010.393 21 25 CVn STF 1768 13375+3618 98.3 1.76 2010.406 29 25 CVn STF 1768 13375+3618 96.6 1.78 2011.315 58 25 CVn STF 1768 13375+3618 96.5 1.78 2011.340 14 25 CVn STF 1768 13375+3618 96.5 1.65 2012.301 55 25 CVn STF 1864AB 14407+1625 111 5.53 2010.387 20 π Boo STF 1864AB 14407+1625 110.8 5.54 2010.390 21 π Boo STF 1864AB 14407+1625 110.8 5.61 2011.348 11 π Boo STF 1864AB 14407+1625 110.9 5.57 2011.354 38 π Boo STF 1864AB 14407+1625 110.7 5.55 2012.375 56 π Boo

Table continues on next page.

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Double Star Measurements Using A Small Refractor

Name RA & De PA Sep Date No Notes STF 1877AB 14450+2704 343.3 2.94 2010.385 24 ε Boo STF 1877AB 14450+2704 342.3 2.94 2010.387 14 ε Boo STF 1877AB 14450+2704 342.7 2.94 2011.346 36 ε Boo STF 1877AB 14450+2704 342.2 2.97 2011.376 30 ε Boo STF 1877AB 14450+2704 343.8 2.78 2012.400 81 ε Boo STF 1877AB 14450+2704 342.9 2.88 2012.402 81 ε Boo STF 1888AB 14514+1906 308.1 6.1 2010.420 46 ξ Boo STF 1888AB 14514+1906 307 6 2011.354 20 ξ Boo STF 1888AB 14514+1906 307.3 6 2011.362 21 ξ Boo STF 1888AB 14514+1906 305.5 5.8 2012.375 79 ξ Boo STF 1888AB 14514+1906 305.6 5.73 2012.454 36 ξ Boo STT 288 14534+1542 159.8 1.16 2010.426 20 STT 288 14534+1542 159.7 0.97 2011.409 36 STT 288 14534+1542 160.9 1.09 2011.417 19 STT 288 14534+1542 159.4 0.95 2011.419 31 STT 288 14534+1542 160.9 1.09 2012.455 32 STT 288 14534+1542 159.3 0.97 2012.463 48 STF 1909 15038+4739 60.2 1.62 2010.423 49 44 Boo STF 1909 15038+4739 61.3 1.51 2011.391 42 44 Boo STF 1909 15038+4739 60.6 1.39 2011.395 43 44 Boo STF 1909 15038+4739 60 1.46 2011.403 67 44 Boo STF 1909 15038+4739 60.7 1.38 2012.383 117 44 Boo STF 1909 15038+4739 62.4 1.4 2012.391 118 44 Boo STF 1909 15038+4739 62.8 1.34 2012.397 123 44 Boo STF 1909 15038+4739 62.5 1.31 2012.438 79 44 Boo STF 1932AB 15183+2650 263.7 1.53 2012.517 10 STF 1932AB 15183+2650 264 1.57 2012.558 31 STF 1931AB 15187+1026 166.4 13.38 2012.436 15 STFA 28AB 15245+3723 170.7 108.8 2010.390 25 μ Boo STFA 28AB 15245+3723 170.8 108.79 2010.407 24 μ Boo STFA 28AB 15245+3723 170.9 108.8 2011.387 44 μ Boo STF 1938BC 15245+3723 5.4 2.27 2010.404 11 μ Boo STF 1938BC 15245+3723 5.9 2.32 2011.389 38 μ Boo STF 1938BC 15245+3723 4.8 2.23 2011.392 17 μ Boo STF 1938BC 15245+3723 6.1 2.3 2011.395 20 μ Boo STF 1938BC 15245+3723 4.9 2.2 2012.408 32 μ Boo STF 1954AB 15348+1032 172.6 3.92 2012.487 81 δ Ser STF 2021AB 16133+1332 356.8 4.13 2012.564 39 49 Ser STF 2032AB 16147+3352 238 6.95 2012.517 35 σ CrB STF 2032AB 16147+3352 238 6.94 2012.558 39 σ CrB STFA 30AC 16361+5255 193.3 90.11 2012.588 22 16&17Dra STF 2078AB 16361+5255 104.3 3.07 2012.588 31 17 Dra STF 2118AB 16564+6502 65.9 0.95 2012.610 41 20 Dra STF 2118AB 16564+6502 67.4 0.93 2012.613 60 20 Dra STF 2130AC 17053+5428 7.5 2.46 2010.716 39 μ Dra STF 2130AC 17053+5428 6.9 2.47 2011.740 58 μ Dra

Table continues on next page.

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Double Star Measurements Using A Small Refractor

Name RA & De PA Sep Date No Notes STF 2130AC 17053+5428 5.7 2.39 2012.504 77 μ Dra STF 2140AB 17146+1423 103.7 4.82 2010.461 49 α Her STF 2140AB 17146+1423 103.6 4.86 2011.644 40 α Her STF 2161AB 17237+3709 320.3 4.11 2010.478 40 ρ Her STF 2161AB 17237+3709 320 4.11 2011.644 75 ρ Her STF 2161AB 17237+3709 320.1 3.94 2012.556 34 ρ Her STF 2161AB 17237+3709 319.6 3.97 2012.558 31 ρ Her STFA 35 17322+5511 310.9 62.03 2012.591 29 ν Dra STF 2199 17386+5546 55.7 2.06 2012.591 46 STF 2199 17386+5546 56.2 2.06 2012.610 24 STF 2220AB 17465+2743 249.9 34.72 2010.486 4 μ Her H 6 2 AC 18006+0256 142 54.38 2012.501 21 67 Oph STF 2264 18015+2136 256.7 6.15 2012.561 42 95 Her STF 2272AB 18055+0230 130.8 6 2010.508 37 70 Oph STF 2272AB 18055+0230 130.5 5.9 2010.532 22 70 Oph STF 2272AB 18055+0230 130.9 5.86 2010.538 39 70 Oph STF 2272AB 18055+0230 129.7 5.98 2011.633 57 70 Oph STF 2272AB 18055+0230 128.5 5.9 2012.495 46 70 Oph STF 2272AB 18055+0230 128 5.84 2012.501 36 70 Oph STF 2272AB 18055+0230 128 5.85 2012.564 40 70 Oph STF 2323AB 18239+5848 349 3.82 2012.506 64 39 Dra STF 2323AC 18239+5848 19.3 88.84 2012.506 54 39 Dra STF 2316 18272+0012 320.4 3.61 2012.567 28 59 Ser STT 358AB 18359+1659 149.9 1.63 2012.561 27 STT 358AB 18359+1659 150.5 1.64 2012.569 20 STT 358AC 18359+1659 235.3 198.73 2012.569 8 STF 37AC 18443+3940 172.1 208.8 2011.488 43 ε&5 Lyr STF 37AC 18443+3940 171.7 208.59 2012.498 21 ε&5 Lyr STF 2382 18443+3940 347.9 2.37 2010.546 52 ε Lyr STF 2382 18443+3940 348 2.36 2011.518 36 ε Lyr STF 2382 18443+3940 347.8 2.35 2011.537 45 ε Lyr STF 2383 18443+3940 77.6 2.42 2010.546 46 5 Lyr STF 2383 18443+3940 78 2.38 2011.518 37 5 Lyr STF 2383 18443+3940 77.5 2.44 2011.537 36 5 Lyr STTA 182AB 19268+5009 297.3 73.21 2012.750 38 STFA 46AB 19418+5032 133.2 39.68 2012.728 40 16 Cyg STFA 46AB 19418+5032 133.2 39.69 2012.747 27 16 Cyg STF 2579AB 19450+4508 224.9 2.78 2010.598 22 δ Cyg STF 2579AB 19450+4508 224.3 2.3 2011.636 15 δ Cyg STF 2579AB 19450+4508 225 2.61 2012.649 41 δ Cyg STF 2576AB 19456+3337 158.8 2.98 2012.750 38 STF 2578AB 19457+3605 124.7 14.86 2012.750 38 STF 2580AB 19464+3344 68.2 26.05 2012.728 28 17 Cyg STF 2580AB 19464+3344 68.3 26.05 2012.747 19 17 Cyg STF 2580AC 19464+3344 124.4 108.53 2012.728 24 17 Cyg STF 2580AC 19464+3344 124.3 108.53 2012.747 18 17 Cyg

Table concludes on next page.

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Double Star Measurements Using A Small Refractor

Name RA & De PA Sep Date No Notes S 726AD 19466+3253 191.1 29.22 2012.747 21 STF 2583AB 19487+1149 104.6 1.5 2010.563 60 π Aql STF 2583AB 19487+1149 103.1 1.47 2011.584 51 π Aql STF 2583AB 19487+1149 103.9 1.38 2012.556 41 π Aql STF 2583AB 19487+1149 104.2 1.38 2012.567 38 π Aql STF 2725 20462+1554 11.2 6.15 2012.676 43 STF 2727 20467+1607 265.4 8.98 2012.673 37 γ Del STF 2727 20467+1607 265.8 9 2012.676 38 γ Del STF 2758AB 21069+3845 151.6 31.35 2010.579 45 61 Cyg STF 2758AB 21069+3845 151.9 31.45 2011.718 48 61 Cyg STF 2758AB 21069+3845 152 31.4 2012.657 72 61 Cyg STT 432 21143+4109 114.9 1.26 2012.684 39 STT 437 21208+3227 19.5 2.48 2012.660 38 STF 2822AB 21441+2845 312 1.8 2010.598 34 μ Cyg STF 2822AB 21441+2845 315.2 1.69 2011.666 42 μ Cyg STF 2822AB 21441+2845 316.1 1.69 2012.660 49 μ Cyg STF 2863AB 22038+6438 274.9 8 2012.802 42 ξ Cep STF 2909 22288-0001 168.1 2.21 2010.779 46 ζ Aqr STF 2909 22288-0001 168.3 2.1 2011.805 73 ζ Aqr STF 2909 22288-0001 166.7 2.17 2012.775 34 ζ Aqr STF 58AC 22292+5825 191.3 40.63 2012.802 40 δ Cep HJ 1823AC 22518+4119 337.2 81.9 2012.824 25 HJ 1823AE 22518+4119 262.7 118.98 2012.824 22 STF 2978 23075+3250 144.7 8.32 2012.775 39

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Lucky Imaging Astrometry of 59 Andromedae

Bobby Johnson1, Sophia Bylsma1, Cameron Arnet1, Everett Heath1, Jason Olsen1, Anna Zhang1, Kaela Yancosek1, Russell Genet2, 3, 4, Jolyon Johnson5, and Joe Richards2

1. Arroyo Grande High School 2. Cuesta College, San Luis Obispo 3. California Polytechnic State University 4. University of North Dakota 5. California State University, Chico

Abstract: Students from Arroyo Grande High School, as members of a Cuesta College research seminar, observed the double star 59 Andromedae (02109+3902 STF 222) using the lucky imag- ing technique. The measured separation was 16.16” and the position angle was 36.33°. The pair has maintained approximately the same separation and position angle since observations began in 1873. Consideration of historic observations, proper motion vectors, and parallaxes were in- sufficient to conclude whether the double was a chance optical double, a gravitationally bound binary, or a common proper motion pair.

Introduction This paper reports on one of four double star re- search projects that were part of the Fall 2012 Cuesta College Astronomy Research Seminar held at Arroyo Grande High School. Observations were conducted at the Orion Observatory near Santa Margarita Lake, Cali- fornia, on the nights of November 11 and 12, 2012 (B2012.865 and B2012.868) with a Sidereal Technol- ogy controlled 10-inch Meade LX200 telescope equipped with an Andor Luca-S electron-multiplying CCD camera. The primary objective of this project was to add a current observation of the position angle and separation Figure 1: From left to right: Bobby Johnson, Everett Heath, Sophia of 59 Andromedae to the growing set of observations Bylsma, Cameron Arnet, Kaela Yancosek, and Jason Olsen. that began over two centuries ago. The secondary ob- jectives were to provide students with an opportunity to the double star is likely optical or binary in nature. collect data utilizing lucky imaging (an advanced tech- The double star 59 Andromeda (WDS nique), reduce and analyze their data, and determine if 02109+3902 STF 222) was chosen as a wide pair ap-

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Lucky Imaging Astrometry of 59 Andromedae

propriate for observation without supplemental magni- (SBIG) ST-402 CCD camera, provided field identifica- fication. Three sets of observations were made as de- tion and initial centering. tailed below: (1) drifts to determine the camera’s angle A high-speed Andor Luca-S electron multiplying with respect to north, (2) observations of two standard CCD camera was used (unfiltered and without any Bar- double stars to determine both the camera’s orientation low lens) for lucky imaging astrometry. This camera’s and pixel plate scale, and (3) observations of 59 Andro- high speed is achieved, in part, through a software- medae itself. selectable Region of Interest (RoI), allowing just a small portion of the overall pixel array to be read out. Lucky Imaging Normally, reading out a CCD camera at high speed The atmosphere is composed of many small air is much noisier than at slow speeds due to the inherent cells of slightly different temperature and density (Fried nature of analog-to-digital (A/D) converters. However, 1966, Tatarski 1961). Each cell is typically about eight by adding a special row of pixels to the chip just before inches across. The cells deflect the path of starlight as the A/D converter, with each pixel in this row being at they move across the telescope’s field-of-view, causing a slightly higher voltage level than its predecessor, the the rapid movement of stars (jitter) which blurs the electron charges corresponding to the observed light star’s image during normal exposures. This degrading levels can be multiplied by a factor of up to 1000 as effect of “seeing” can be reduced by locating telescopes they are clocked through this electron multiplying row. on high altitude mountaintops. Although this amplification in itself introduces some For a very small area of the sky, about 10 arc sec- noise, for high speeds and low light levels this added onds in diameter, known as an “isoplanatic patch,” the noise is small compared to the high speed read noise of effects of poor seeing can be greatly reduced through the A/D converter and, as a result, the overall noise is lucky imaging or speckle interferometry (Law 2006). greatly reduced from what it would have been without Within the isoplanatic patch, the jitter motion of stars is electron multiplication (EM). correlated—i.e. stars move together. By taking very Finally, it might be noted that although EM can short exposures (10 to 30 milli-seconds) it is possible to greatly reduce overall noise at high speeds, at the slow essentially “freeze” the images and thus remove the tip- readout speeds of many CCD applications the read tilt portion of the atmospheric blurring (seeing) effects noise is comparatively low and EM can actually in- (Anton 2012). crease overall noise. The Andor Luca-S camera has Even then, most images are still blurry. Fortu- two different selectable outputs—one with and one nately, a small percentage can be quite clear. However, without EM, allowing the camera to be used in a mode due to the short exposures, these few clear exposures are also faint. Lucky imaging simply takes many short exposures, saves the best ones, and discards the rest of them. Since the small percentage of clear exposures still “bounce” around from one exposure to the next due to atmospheric jitter, they have to be individually aligned. Once aligned, the images can then be “stacked,” essentially adding all the clear images to- gether to form a final, brighter and higher signal/noise ratio, single image. The selection of the clearest im- ages (from hundreds or even thousands) and aligning and stacking these images has been automated. Equipment and Software At the Orion Observatory, a 10-inch, f/10 Schmidt- Cassegrain telescope, made by Meade and equipped with a Sidereal Technology control system, was used to make the observations. An 80 mm guide scope, Figure 2: Sophia Bylsma, Anna Zhang, and Everett Heath at the equipped with a Santa Barbara Instruments Group Orion Observatory. The Andor Luca-S high-speed emCCD cam- era can be seen just below the telescope.

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Lucky Imaging Astrometry of 59 Andromedae

suitable to the situation at hand. pixel values. The exposures were then rank-ordered, The telescope was controlled with hardware and and the top 10% of the images were saved while the software supplied by Sidereal Technology. Software lower 90% were discarded. The remaining images (50 Bisque’s The Sky 6 was used as the “planetarium” pro- of 500) were then aligned and stacked. With the posi- gram, while the SBIG ST-402 camera was controlled tion angle and separation of the calibration pair known, with Software Bisque’s CCD Soft. The Andor Camera the camera position angle and plate scale (arc seconds was controlled with Andor’s SOLIS. The data was ini- per pixel) for each set were provided by REDUC, and tially gathered as data cubes in the Andor camera’s na- we calculated the means, standard deviations, and stan- tive .sif format. A SOLIS batch conversion process was dard errors of the mean across the four sets. used to transform and unpack the cubes to produce in- Our calibration results are shown in Table 1. The dividual .fit images. Finally, the data was analyzed with calibration pair STT 547 provided the most precise re- REDUC, a sophisticated freeware double star analysis sults, with standard deviations of less than one half of program developed by Florent Losse, a very active dou- those of the other calibration pair, STF 742, and (for ble star observer in France. the camera angle) less than one third that of the drifts. While we could have used some precision-weighted Calibration means to combine all three of our calibration results, Calibration observations were made on the second we chose instead to exclusively utilize the most precise night. The camera had not been moved in any way be- results, those of STT 547. tween the two nights. “Drifts” were obtained by mov- Although we are reasonably confident in the preci- ing a bright star to one edge of the camera’s field and sion of our three calibration results, as given in Table 1, then temporarily turning off the telescope’s drive, caus- they are in disagreement in their means beyond the one ing the star to drift across the field-of-view as the Earth sigma level, suggesting a systematic difference. This turned while multiple images were taken. A feature of could have been a result of the calibration pairs not be- REDUC provides a least squares fit of a straight line ing positioned sufficiently close in the sky to the pro- through the star’s centroids on the multiple images, gram pair, and hence inaccuracies in the polar align- thus establishing an east-west line from which the ori- ment of the telescope could have affected accuracy, as entation (angle) of the camera with respect to North can the field will rotate with changes in the telescope’s po- be deduced. Five drifts were obtained so we could sition with poor axis alignment. estimate the precision (standard error of the five means) There were insufficient calibration observations to with which the camera’s angle with respect to celestial estimate their accuracy; we expect that their accuracy north was being determined. could be less than could have been achieved for two Observations were also made of two calibration reasons. First, observations of the program star (59 An- binary stars, STF 742 and STT 547. These binaries dromedae) were made on the first night, while calibra- have well-established orbits and, at any point in time, tion observations of the two calibration binaries were their position angle and separation can be determined made on the second night. Although we were careful via simple interpolations from a catalog of ephemerides not to move the camera in any way during the two provided by the U.S. Naval Observatory. We per- nights (and seeing and other observing conditions were formed these interpolations. We calculated these for similar), if our program observations had been brack- STF 742 as a position angle of 275.2 degrees and a separation of 4.1 arc seconds. These values for STT 547 were, respectively, 187.2 degrees and 5.9 arc sec- Table 1: Calibration results: The camera angles and scale onds. Two different ephemerides were reported in the factors and standard deviations. Sixth Orbit Catalog - we used the first one. Each cali- Scale Angle One Sigma Factor One Sigma bration binary observation consisted of 2000 exposures (degrees) Std. Dev. (Arcsec/ Std. Dev. which we divided into four sets of 500 exposures. Each Pixel) set was then analyzed with REDUC for the “best” ex- Drifts -7.63 0.25 N/A N/A posures, using the “brightest pixel” technique. The light on the poor, blurry images is more spread out, STF 742 -8.33 0.19 0.229 0.0008 while sharp images have concentrated light with higher STT 547 -7.93 0.07 0.222 0.0003

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It is instructive to compare, for the same total inte- Table 2. Separation, position angle, and difference in mag- nitude measurements for 59 Andromedae with the averages, gration time, what the image looks like with and with- standard deviations, and standard errors of the mean. out lucky imaging. Figure 3, left, shows the image that results from stacking all 500 frames of the first set Besselian Sep. Frames PA (°) dMag Epoch (arc sec) without any selection or alignment—the “raw” image. B2012.865 000-499 16.156 36.18 1.08 The image on the right is of the best 50 of the 500 frames shown after both alignment and stacking—the B2012.865 500-999 16.136 36.44 1.10 lucky image. The lucky image is much more sharply B2012.865 1000-1499 16.167 36.38 1.07 defined (higher resolution) and, as a result, provides astrometry of significantly higher precision. B2012.865 1500-1599 16.209 36.27 1.06 These two images clearly demonstrate how B2012.865 2000-2499 16.149 36.40 1.07 well lucky imaging can overcome atmospheric distor- tions (not to mention poor tracking). Because the cen- Average 16.160 36.33 1.08 troids of the individual stars can be more precisely de- St. Dev. 0.03 0.11 0.02 termined with lucky imaging, it follows that the posi- tion angle and separation will also be more precise. St. Err. Mean 0.01 0.05 0.01 Furthermore, if the separation of the two stars had been so close that the raw image stars were merging together eted with calibration observations we could have devel- into a single image, the stars in the lucky image could oped confidence in the constancy of the camera’s orien- still have been resolvable and usable. Thus lucky im- tation and pixel plate scale. aging not only allows higher precision, but also closer doubles to be measured. Program Observations Altogether 2500 frames (images) were re- Comparison with Previous Observations corded for 59 Andromedae. Similar to the calibration William Herschel, in 1783, was the first astronomer doubles, we split the data into sets of 500 frames each, to report the separation and position angle of the 59 applied REDUC’s “best of max” brightest pixel sorting Andromedae pair (Smyth 1844). John Herschel and to each of the five sets, saved the best 10% (50 frames James South observed this double in 1822 (South and from each set), and aligned and stacked these images. Herschel 1824). Friedrich von Struve, for whom the Assuming the camera angle and plate scale provided STF designation was given, observed 59 Andromedae from our observations of the calibration pair STT 547, twice, in 1822 and 1831 (Struve 1837). Recently, David we obtained the program results shown in Table 2. Arnold visually observed the pair in 2005 (Arnold

Figure 3: Left is the first 500 images just stacked. Right is the best 10% of the first 500 images (i.e. 50 images) stacked and aligned.

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Lucky Imaging Astrometry of 59 Andromedae

2006). Mason, et al. used speckle interferometry to separation of the past 25 years is 16.68” while our ob- measure this double in 2006, 2007, 2008, and 2011 served separation in the present study was 16.16”, a (Mason, et al. 2007, 2008, and 2010, and Mason and 0.52” difference. The average position angle of the past Hartkopf 2013). A total of 83 measurements of separa- 25 years is 35.60° while our observed position angle in tion and 85 of position angle have been made since the present study was 36.33°, a 0.73° difference. 1783. Another way of considering comparisons with pre- This double does not have an ephemeris in either vious observations is viewing visual plots. Ed Wiley the Sixth Orbit Catalog or the Catalog of Rectilinear kindly plotted our data using a spreadsheet developed Elements. To consider, roughly, the accuracy of our by Francisco Rica Romero. The observations were cor- measured separation and position angle, an average of rected for precession and proper motion prior to plot- observations over the last 25 years was used as a com- ting and converted to Cartesian coordinates. X and Y parison. The past observations were supplied by Brian plots versus epoch are shown in Figures 4 and 5, while Mason at the US Naval Observatory. The average Figure 6 is a cluster plot of the X/Y positions without STF222 X versus Epoch 13 12 11 10 X 9 1783‐2011 8 2012.865 7 6 1750 1800 1850 1900 1950 2000 2050 Epoch

Figure 4: X values versus epoch. Open circles are previous observations, while the filled square is our observation STF 222 Y versus Epoch 17 16 15 14 Y 13 1783‐2011 12 2012.865 11 10 1750 1800 1850 1900 1950 2000 2050 Epoch

Figure 5: Y values versus epoch.

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Lucky Imaging Astrometry of 59 Andromedae

STF222 Cluster Plot 18.0 16.0 14.0 12.0 10.0 Y 8.0 1783‐2011 6.0 2012.865 4.0 2.0 0.0 0.0 5.0 10.0 15.0 X

Figure 6: Cluster plot of X and Y positions plotted as a cluster without epoch information. The result is a fairly tight cluster. Our observation is not an outlier.

respect to epoch. each just one tenth of a “class” away from A0. Since their spectral types are so similar and both are on the Is 59 Andromedae an Optical Double or a Bi- main sequence, the stars could be roughly the same dis- nary? tance from Earth. All nine measurements from the first 50 years of On the other hand, SAO 55330 has a parallax of observation, beginning in 1822, were averaged to deter- 0.01241” ± 0.00283” which corresponds to a distance mine how the pair has changed over time. The average of 263 light years (SIMBAD 2012). SAO 55331 has a separation of the first 50 years, as show in Table 3 is parallax of 0.00192” ± 0.01175” which yields a dis- 16.53”, a 0.15” difference from the average over the tance of 1699 light years (SIMBAD 2012). However, last 25 years. The average position angle of the first 50 the error for the secondary star's distance is sizable, years is 34.89°, a 0.71° difference from the last 25 ranging from 236 light years to infinity (SIMBAD years. Both differences are within a single standard 2012). Thus, based on parallaxes, it is possible, though deviation and are therefore insignificant. unlikely, that the two stars are at the same distance The spectral type of 59 Andromedae’s primary from Earth. If both stars were 263 light years from component (SAO 55330) is B9V and its magnitude is earth (and the average separation of the past 25 years of 6.05 (SIMBAD 2012). The spectral type of the secon- 16.68” is correct), they would be ~1.22 light years dary component (SAO 55331) is A1V and its magni- (77,154AU) apart—perhaps too far apart to be gravita- tude is 6.71 (SIMBAD 2012). The B9 and A1 stars tionally bound, but close enough to be a common probably have a similar brightness because they are proper motion pair.

Table 3: Average separation and position angle for observations in the first 50 years and last 25 years with standard deviations and standard errors of the mean. First 50 Years Last 25 Years Diff First 50 Years Last 25 Years Diff.

Sep (“) Sep (“) (“) PA (°) PA (°) PA (°) Average 16.53 16.68 0.15 34.89 35.60 0.71

St. Dev. 0.37 0.92 0.93 0.90 St. Err. Mean 0.07 0.17 0.17 0.17

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Lucky Imaging Astrometry of 59 Andromedae

Finally, double stars are most likely binary if the positional plots. In addition, we made use of the U.S. proper motion vectors of the two stars are similar. The Naval Observatory’s Washington Double Star Catalog proper motion (in milliarcseconds per year) of SAO and the SIMBAD data base at CDS. We thank our ex- 55330 is -7.99 in RA and -19.97 in Dec (SIMBAD ternal reviewers: Rainer Anton, Robert Buchheim, Tho- 2012). The proper motion of SAO 55331 is -7.60 in RA mas Frey, John Martinez, Tom Smith, Vera Wallen, and -21.52 in Dec (SIMBAD 2012). These values are and Ed Wiley. Finally, we would like to thank the of similar magnitude and direction, suggesting that 59 Orion Observatory for the use of their equipment and Andromedae may be binary or at least a common hospitality. proper motion pair. References Conclusions and Recommendations Anton, Rainer, 2012, Lucky imaging. In Observing and While some of Cuesta College’s Astronomy Re- Measuring Visual Double Stars 2nd Edition, Robert search Seminar projects continued this fall to make Argyle, ed., Springer, New York. double star measurements with astrometric eyepieces as in the past, this was the first semester we employed the Arnold, Dave, 2006, Divinus Lux Observatory Bulletin: more advanced and precise technique of lucky imaging. Report #6. Journal of Double Star Observations., We were pleased with our results and recommend that 2, 87. at least some future teams continue to use the Andor Fried, D. L., 1966, Optical resolution through a ran- Luca-S high speed EMCCD camera for their projects. domly inhomogeneous medium for very long and In analyzing whether or not 59 Andromedae is very short exposures, Optical Society of America merely a chance optical double, a gravitationally bound Journal, 56, 1372. binary, or a common proper motion pair, we were un- able to draw a decisive conclusion due to the conflict- Johnson, Jolyon, 2008, Double star research as a form ing brightness, parallax, and proper motion evidence. of education for community college and high We recommend that future projects improve on our school students. In Proceedings for the 27th Annual calibration procedures by observing nearby calibration Conference for the Society for Astronomical Sci- standards both before and after program pair observa- ences. Brian Warner, Jerry Foote, David Kenyon, tions. Future student projects might consider reporting and Dale Mais, eds., Society for Astronomical Sci- on more than one program double in a single paper. ences, Big Bear, CA. They could also observe much closer doubles. Law, Nicholas, 2006, Lucky imaging: diffraction- Finally, future projects might attempt to observe limited astronomy from the ground in the visible. very close doubles. Rainer Anton suggested that an Doctoral dissertation, Cambridge University. interesting comparison could be made between lucky imaging observations of a fairly faint, close double with Mason, Brian D., William I. Hartkopf, Gary L. Wycoff, and without the camera’s electron multiplication. In- and G Wieder. 2007. Speckle Interferometry at the stead of lucky imaging, a student team might attempt US Naval Observatory, XIII. Astronomical Jour- speckle interferometry, although this could require sig- nal. 134:4, 1671. nificant supplemental magnification to bring out the Mason, Brian D., William I. Hartkopf, and Gary Wy- “speckles.” In addition to magnification, use of a filter coff, 2008, Speckle Interferometry at the US Naval to limit the bandwidth and chromatic effects might Observatory, XIV, Astronomical Journal, 136, sharpen the speckles. 2223. Acknowledgments Mason, Brian D., William I. Hartkopf, and Gary Wy- We thank Florent Losse for use of his REDUC soft- coff, 2010, Speckle Interferometry at the US Naval ware, the American Astronomical Society for providing Observatory, XV, Astronomical Journal, 140, 480. a Small Research Grant to purchase the Andor Luca-S Mason, Brian D. and William I. Hartkopf, 2013, Astro- camera, Andor for supplying the camera at a discounted nomical Journal, in press. cost, and Jordan Fluitt for aiding us in observations. We thank Ed Wiley and Francisco Rica Romero for the

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Lucky Imaging Astrometry of 59 Andromedae

SIMBAD Astronomical Database, Centre de Données Astronomiques de Strasbourg. December 7, 2012. simbad.u-strasbg.fr/simbad/. Smyth, William, 1844, Cycle of Celestial Objects Vol- ume 2. South, James and John Herschel, 1824, Observations of the apparent distances and positions of 380 double and triple stars, made in the years 1821, 1822, and 1823, and compared with those of other astrono- mers; Together with an account of such changes as appear to have taken place in them since their first discovery. Also a description of a five-feet equato- rial instrument employed in the observations, Phi- losophical Transactions of the Royal Society, 114, 1-412. Tatarski, V., 1961, Wave Propagation in a Turbulent Medium, McGraw-Hill, New York. von Struve, Friedrich Wilhelm, 1837, Stellar duplicium et multiplicium mensurae micrometricae, Petropoli.

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Useful Lists of Double Stars

Joseph M. Carro

Cuesta College San Luis Obispo, California

Abstract: The study of double stars often involves searching through several references in order to obtain information. This time consuming process could be greatly shortened if the information were summarized into spread sheets from which data could be easily extracted. To that end, I have prepared four lists: a catalog of 4,765 double stars, a single list of the entire OAG and all of its supplements, a summary of the Washington Double Star Catalog, and a partial cross reference of identifiers.

2. Method Objectives All of the information was copied, not transcribed, In my studies of double stars, it is often necessary from original sources, and mounted into an Excel book to search through several sources to find information, consisting of 93 sheets, and saved in the 2010 and the which is a very slow process. Two approaches to im- 97-2003 format. All of the data is unmodified, and pre- proving this situation were taken. The first objective sented as shown in the original source, however, the was the compilation of a double star catalog with infor- reader should note that when data is copied, Excel often mation and major identifiers for a large number (4,765) omits leading and trailing zeroes. The absence of data of double stars. The second objective was to organize merely means that no data was available from the origi- existing catalogs into a more useful format. nal source. The Carro Double Star Catalog The magnitude of the primary star will be 12 or brighter, making it possible to view these stars with 1. Description small telescopes. Star selections were made from each The Carro Double Star Catalog contains the names of the 88 constellations. Links to the data files were of 4,765 double stars along with four major identifiers, placed on the Home Page of the Journal of Double Star namely the Bonner Durchmusterung number (BD), the Observations. The files may be downloaded from that Discoverer Code (DC), the Smithsonian Astrophysical web site (http://www.jdso.org/), and freely distributed. Observatory (SAO) number, and the Washington Dou- 3. Organization ble Star (WDS) identifier. The BD, DC, and WDS The star names are displayed in the following or- numbers were taken from the Washington Double Star der: number designation (2 CAS), Greek letter (iota Catalog. The SAO number was taken from the SIM- CAS), number and Greek letter (24, eta CAS), number, BAD web site. Some other references were consulted. Greek letter and traditional name (18, alpha CAS

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Useful Lists of Double Stars

Schedar). A name such as 18 alpha CAS Schedar means and their web site has four pages on which the double that the star may be found in other catalogs by its num- star information is given. This fact means that searching ber (18 CAS), its Greek letter designation (alpha CAS), for information often means looking at more than one or its traditional name (Schedar). If no such nomencla- page. Furthermore, the data was mounted in text format ture existed, the discoverer code was used (such as BU with all of the data in a single string which requires con- 1094). Greek letters are shown in lower case, and con- version into other formats. stellation abbreviations are shown in upper case. There All four pages were combined into a single spread is some inconsistency in the names as they were taken sheet using Excel version 2010. This format makes any from several sources, not all of which agree with each search easier, and the table can be resorted in accord other. with the wishes of the investigator. This flexibility gives The following information is given for each entry: any investigator the opportunity to sort based on criteria star name, SAO number, WDS identifier, discoverer that are under study. code and number, Bonner Durchmusterung number, The Observatorio Astronómico de Garraf components, date of first satisfactory observation, date This catalog was coordinated by Tofol Tobal and of most recent satisfactory observation, number of ob- Jaume Planas of the Garraf Astronomical Observatory, servations, position angle at observation 1, position an- Barcelona, Spain, and is available from the web site of gle at observation 2, separation at observation 1, separa- the United States Naval Observatory. On that site, the tion at observation 2, magnitude of first component, original catalog and 26 supplements can be found. The magnitude of second component, spectral type primary/ fact that there are 27 pages makes data searches awk- secondary, primary proper motion (RA1), primary ward and slow because there is no way to know on proper motion (DE1), secondary proper motion (RA2), which page a star might be listed. secondary proper motion (DE2), right ascension J2000, The original list and all of the supplements were and declination J2000. combined into a single Excel spread sheet, which was Within the Excel book there is a sheet for each con- then sorted by the WDS coordinates, a fact which stellation, and those sheets are sorted in alphabetical greatly facilitates any search. order. Within each constellation sheet, the star names Identifier Cross Reference are sorted in alphabetical order. A diagram of each con- A partial list of 12 identifiers linked to the WDS stellation accompanies the star data. Each star name is identifier was compiled. No attempt was made to in- also a link to the SIMBAD web site from which addi- clude all of the identifiers as there are currently up to 74 tional information is available. identifiers for a given star. At the end of the catalog will be found tables which were sorted by 1) constellation and then star name, 2) Use star name, 3) Washington Double Star identifier, and 4) Due to the fact that the lists were prepared using Right Ascension. Two other tables were included, Excel version 2010, the data is also available in an easily namely a list of some colored stars, and the best viewing managed format. Any portion of the data may be copied times for the constellations. See Figures 1 and 2. and exported to other programs such as Microsoft Word, 4. Sources electronic mail software, or other spread sheet software. The primary sources for this work included the Once imported into a local spread sheet, new sheets may Washington Double Star Catalog (edited by Brian Ma- be created, and operators will be able to keep unique son), the SIMBAD web site which is maintained by portions of the data on separate sheets. Centre de Données Astronomiques de Strasbourg Acknowledgements (Cécile Loup, web master), the Eagle Creek Observatory This research made use of the Washington Double web site (Kevin Muenzler web master), and the Bright Star Catalog maintained by the United States Naval Ob- Star Catalog. Some of the star data was obtained from servatory, and the SIMBAD data base operated at CDS, other sources. Strasbourg, France. The Washington Double Star Catalog The United States Naval Observatory is the agency charged with the task of maintaining the WDS Catalog, (Continued on page 206)

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Useful Lists of Double Stars

Ant- Double Stars of the Constellation ANTLIA (the Air Pump) ANT liae

Antlia is a southern constellation which rises in October, sets in June, and is best viewed in Febru- ary.

To obtain more information about a star, left click on the star name and the SIMBAD site will open.

First Latest PM PM PM PM

Star RAJ20 DEJ20 SAO WDS Disc DM Com Obs1 Obs2 Ob pa1 pa2 Sep1 Sep2 mag1 mag2 Sp Type RA1 DE1 RA2 DE2 name 00 00

09569- -27 09 56 ARG 23 ARG 23 1883 1999 4 84 80 57.5 56.1 8.73 11.3 A8/9V 13 -26 2832 7069 55.11 -28 32 27.4

09360- -26 09 36 B 185 177722 B 185 AB 1926 1999 13 204 201 3.7 3.2 7.57 9.66 A4III -41 9 -41 4 2731 7251 02.93 -27 31 19.2

09541- -27 09 54 BU 215 178157 BU 215 AB 1874 1991 16 340 346 1.5 1.8 7.15 9.32 B4V -14 -5 -14 -5 2800 7035 05.14 -27 59 56.4

-30 delta 10296- -29 10 29 201442 H N 50 AB 1834 1999 22 235 226 10 10.9 5.56 9.84 B9.5V -31 6 -29 2 36 ANT 3036 8383 35.38 25.4

-35 09589- -35 F1III- 09 58 eta ANT 200926 HJ 4271 1836 1999 7 313 319 27.5 31.4 5.23 11.3 -87 -20 53 3553 6050 IV 52.34 27.4

-36 09332- -35 09 33 HJ 4218 HJ 4218 1836 1999 13 27 29 3.5 5.7 7.62 9.78 A1IV -10 -21 1 -3 24 3624 5778 09.84 16.8

-33 10157- -32 10 15 HJ 4300 HJ 4300 1835 1999 13 106 108 7.5 9 9.5 10.16 F3V F3V -40 8 -36 9 16 3317 7182 41.02 46.4

-33 10202- -32 A3III/ 10 20 HJ 4304 201293 HJ 4304 AB 1836 2004 12 290 286 12 9.5 7.55 9.78 -17 9 -24 10 07 3308 7252 IV 13.67 43.4

-30 10417- -30 10 41 HJ 4342 HJ 4342 1834 1999 7 54 55 16.5 25 8.16 10.96 A0V -6 0 45 3045 8634 43.32 01.5

Figure 1: Sample page -- condensed to fit on this page

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Figure 2: Sample constellation diagram

(Continued from page 204) References Diagrams courtesy of www.dudeman.net. Hoffleit, D. and W. Warren, 1991, The Bright Star Catalogue, 5th Revised Edition, Yale University. Google web site http://maps.forum.nu/gm_sky.html McEvoy, B., William Herschel’s Double Star Catalogs Restored, 2011. http://www.handprint.com/ ASTRO/Herschel500.html Mason, B., G. Wycoff, W. Hartkopf, G. Douglass, C. Worley, 2011, Washington Double Star Catalog. Muenzler K., 2003, Eagle Creek Observatory (www.eaglecreekobservatory.org); information used by permission SAO Staff, 1996, Smithsonian Astrophysical Observa- tory Star Catalog. SIMBAD web site, Cécile Loup web master http:// simbad.u-strasbg.fr/simbad/sim-fid

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Visual Astrometry of 35 Cassiopeiae

Joseph Carro,1 Alyssa Adams,2 Garrett Moore,2 Triston Perez,2 Sarah Thomas,2 Oksana Moscoso,3 Krystyn Michaud,1 Joseph Richards,1 Jolyon Johnson,4 and Russell Genet1, 5, 6

1. Cuesta College, San Luis Obispo, California 2. Arroyo Grande High School, Arroyo Grande, California 3. San Luis Obispo High School, San Luis Obispo, California 4. California State University, Chico 5. California Polytechnic State University, San Luis Obispo 6. University of North Dakota, Grand Forks

Abstract: As part of an astronomy research seminar, high school students met with an experi- enced observer to learn astrometric techniques and measure the separation and position angle of the double star 35 Cassiopeiae which they found to have a separation of 59.0ʺ and a position an- gle of 345°. Proper motion vectors suggest this double star is optical rather than binary.

Introduction Known since antiquity, the constellation Cassiopeia is easily recognized due to its characteristic W shape. The double star 35 Cassiopeiae has magnitudes of 6.3 and 8.6. Both stars are blue in color. It was first meas- ured by James South in 1782, at which time the re- ported position angle was 355° and the separation was 50ʺ (Mason 2012). Those values are significantly dif- ferent from the most recent observation (WDS 2010) of 342° and 56.3ʺ. Other identifiers for 35 Cassiopeiae include HD 8003, HIP 6312, SAO 11712, TYC 4038-622.1, and Figure 1: from the left—Krystyn Michaud, Sarah Thomas, Garrett WDS 01211+6439A. Its precise coordinates, as given Moore, Triston Perez, Oksana Moscoso, and Russell Genet outside by the Washington Double Star Catalog, are (J2000) the classroom at Arroyo Grande High School. 01h 21m 05.27s +64° 39m 29.3s. The goals of this project were to: 1) learn the neces- sary techniques to conduct this research, 2) measure the Observations position angle and separation of 35 Cassiopeiae, 3) The observations were made using a Celestron compare our observations with previous observations, model CPC 1100 telescope. This alt-az telescope was and 4) consider whether or not this double star might be computerized and motorized, and was fitted with a Ce- a gravitationally bound binary based on its proper mo- lestron 12.5 mm Micro Guide eyepiece. The telescope tions. is of Schmidt-Cassegrain design with an aperture of 11

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Visual Astrometry of 35 Cassiopeiae

inches. All observations were made in Santa Margarita, California on 11 November 2012 (B2012.865) begin- ning at 7pm Pacific Standard Time. Following the procedure suggested by Teague (2012), the Micro Guide eyepiece was oriented with the celestial coordinate system using the primary star of 35 Cassiopeiae. Once the orientation was completed, ten drift time measurements were made, with an average value of 70.95 seconds, and a standard deviation of 4.96 seconds. That average was used to calculate the scale constant using the formula:

Z = [ 15.0411 * t * cos(δ) ] / D

where Z is the scale constant in arc seconds per divi- sion, 15.0411 is the rotation rate of Earth in arc seconds Figure 2: The observing team with the Celestron telescope used to per second, t is the average drift time of the calibration make the observations (from left): Joseph Carro, Garrett Moore, star in seconds, δ is the declination of the calibration Sarah Thomas, and Triston Perez. star (64.65°), and D is the number of divisions on the linear scale (60). The resulting scale constant was 7.6 tion angle measurement was 3° greater. These differ- arc seconds per division. ences might be reduced in future observations if separa- The primary star was then placed on the linear tion observations were not rounded off to the nearest scale, and eight separation measurements were taken division, and the eyepiece was rotated 180° between and reported to the nearest division. The primary star each position angle measurement to reduce the effects was relocated and advanced on the linear scale prior to of eyepiece alignment error as well as the effects of each measurement. The average value was 7.8 divi- field rotation during observation when using an alt- sions with a standard deviation of 0.46 divisions and a azimuth telescope. standard error of the mean of 0.16 divisions. The aver- One goal of this project was to determine if the age value was used to calculate the angular separation double star 35 Cassiopeiae might be a physically bound of 59.9ʺ. binary system by considering the proper motions of the The position angle measurements were made by two stars. Binary stars have very similar proper motion aligning both stars on the linear scale with the primary vectors, the two dimensional motion of stars through star at the middle, 30th division, disabling the tele- scope’s tracking feature, and allowing the stars to drift Table 1: Past observations of 35 Cassiopeiae compared to the to the circular scales with the Earth's rotation. The results of the present study. crossing point of the primary star at the outer scale was Position approximated to the nearest degree. Following each Reference Separation (“) measurement, the tracking feature was enabled and the Angle (°) process repeated. Eight position angle measurements WDS (Mason+ 2007) 1782 50.0 355 were taken without any rotation of the eyepiece, which WDS (Mason+ 2007) 1824 55.0 353 resulted in an average value of 345.3o, a standard devia- tion of 1.8°, and a standard error of the mean of 0.6°. WDS (Mason+ 2007) 1967 55.5 344 Comparison with Previous Observations and O A G (Comellas 1980) 55.0 345 Analysis Herschel 500 Catalog 57.0 342 Shown in Table 1 are several previous observa- Hipparcos (from SKY X) 57.0 342 tions from 1782 to 2012 as well as our current (2012) WDS (Mason+ 2007) 2010 56.3 342 measurement. Our separation measurement was 2ʺ greater than three recent observations, while our posi- Present Study (2012) 59.0 345

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Visual Astrometry of 35 Cassiopeiae

space. The proper motion of the primary star (SAO References 11712) is 59.75 milliarcseconds per year in right ascen- Arnold, David, 2010, “Considering proper motion in sion and -22.83 mas/yr in declination (SIMBAD 2012). the analysis of visual double star observations”, The proper motion of the secondary star (SAO 11709) Small Telescopes and Astronomical Research, eds., is -5.30 in right ascension and -9.50 in declination R. Genet, J. Johnson, and V. Wallen, Collins Foun- (SIMBAD 2012). These sizable differences in both dation Press, Santa Margarita, CA. proper motion magnitude and direction suggest that 35 Cassiopeiae is probably an optical double and not a bi- Comellas, Observatorio Astronómico de Garraf, (http:// nary system (Arnold 2010). www.oagarraf.net). Conclusions Hipparchos Catalog (from SKY X software) 2000. The students measured the position angle and Mason, B., G. Wycoff, W. Hartkopf, G. Douglass, and separation of the double star 35 Cassiopeiae. In making C. Worley, 2012, Washington Double Star Catalog. the observations, the students learned the necessary techniques to conduct astrometric research of double McEvoy B., William Herschel’s Double Star Catalogs stars. Our accuracy could have been improved if we Restored, 2011. had rotated the eyepiece between position angle obser- Teague, Thomas. 2012. “Simple techniques of measure- vations. Finally, we concluded that this double is not ment”, in Observing and Measuring Visual Double likely binary due to the sizeable difference between its Stars, ed. Robert Argyle, Springer, New York. proper motion vectors. Acknowledgments The authors thank Orion Observatory for the use of its facilities. The authors also thank Brian Mason and the United States Naval Observatory for past obser- vations. Finally, thanks go to Tom Frey and Vera Wallen for their critical reviews of this paper.

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Observing 75 Draco with a Manual Dobsonian Telescope

Joseph Richards Cuesta College

Megan Calabrese, Alexandria Calabrese, and Mckenzie Calabrese Arroyo Grande High School

Abstract: Students from Cuesta College and Arroyo Grande High School measured the position angle and the separation of the double star 75 Draco (WDS 20282+8125) with a manual Dob- sonian telescope. The average position angle was 281.9° while the separation was 196.7ʺ. These values compared favorably to the most recent observation reported in the Washington Double Star Catalog.

through our telescope’s field-of-view, so our separation Introduction measurements would be easier to make on this manual Observations of 75 Draco were made as part of a Cuesta College research seminar held at Arroyo Grande High School. The primary goal of these obser- vations were to compare data gathered on a manual Dobsonian telescope with previous observations gath- ered by other types of telescopes. Secondary goals were to contribute another observation to the series that began in 1884, and to learn the process of scientific research and how to write a scientific paper. Our observations were made with an Orion Sky- Quest XT10 manual Dobsonian telescope, which made it both interesting and challenging to make measure- ments and take accurate data. This telescope has a focal Figure 1: Megan, Mckenzie, and Alexandria Calabrese, and Joe length of 1250 mm and an aperture of 10 inches (254 Richards analyze their 75 Draco data. mm). We used a Celestron Micro Guide 12.5mm astro- metric eyepiece, and a stopwatch that reads to the near- telescope. A disadvantage of far northern positions is est 0.01 seconds for instrumentation. Our observations they increase field rotation between observations, an were taken on Saturday, November 10, 2012 (Besselian effect that is also increased with longer drift times. 2012.86) at Star Hill near Santa Margarita, CA at 35.32 N, 120.49 W. Calibration We chose 75 Draco (WDS 20282+8125 STH 7 AC) To calibrate the Micro Guide eyepiece, we for its far north position, which makes it drift slowly measured the time it took for the star Mirach to drift

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Observing 75 Draco with a Manual Dobsonian Telescope

across the linear scale in the eyepiece. We used the av- erage of three times, the known declination of Mirach, Table 1: Calibration measurements (time in seconds and the number of divisions on the Celestron Micro Guide scale to calculate the scale constant (z) of each Calibration Star Mirach division on the linear scale using the formula from Ar- Drift Time #1 81.13 gyle (2012): Drift Time #2 80.56 15.0411 time  cosdeclination Drift Time #3 80.79 z = Average Drift Time 80.83 divisions Std. Dev. 0.2868 15.041180.83 cos 35.69 Declination +35° 41' 18" z = 60 Declination (decimal) 35.688 Divisions 60 z  16.46 arc seconds per division Scale Constant 16.46

Data used in the calibration is given in Table 1.

Separation We measured the separation of 75 Draco by lining Table 2: Separation measurements up the stars parallel to the linear scale and estimating Observation Divisions Separation ʺ the number of division marks between them. We de- #2 11.8 194.19 leted two outliers. #3 12.0 197.48 Making measurement was challenging on a manual #4 12.0 197.48 Dobsonian telescope. The stars were always drifting, #5 12.0 197.48 which made it difficult to accurately estimate the num- ber of division marks on the linear scale. The advantage #6 12.0 197.48 of a telescope that tracks is that the double stars stay Std. Dev. 0.08 1.38 still in the field-of-view, making them easier to line up Average 11.95 196.66 and measure. To calculate the separation, we used the scale con- stant, which represents arc seconds per division mark, and multiplied it by the estimate of division marks. Table 2 gives the data and results of the separation measurement. Position Angle Table 3: Position angle measurements

The position angle proved more difficult and time Observation Position Angle ° consuming to find than the separation. We lined up ei- ther star in the system in front of the center point on the #1 281.50 th linear scale, the 30 division, and allowed it to drift #2 282.00 through and eventually move out of the view of the #3 281.00 telescope. If the star did not go through the center point, we reset the alignment of the telescope until it did. The #4 283.00 eyepiece was rotated 180 degrees after every two meas- Std. Dev. 0.85 urements to reduce alignment bias and reduce the ef- fects of field rotation. The point that it passed on the Average 281.88

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Observing 75 Draco with a Manual Dobsonian Telescope

Table 4: Results compared to the last reported WDS obser- 1884. The position angle was 285.3° while the separa- vation tion was 198.35ʺ. For the most recent observation in 2000, the reported position angle was 282.1° and the Position Angle ° Separation ʺ separation was 196.60ʺ. Our results came very close to

Last WDS 282.10 196.60 these recently reported values, which leads us to believe that they are reasonably accurate. See Table 4. Our Observation 281.88 196.66 In Figures 2 and 3, the previous WDS observations Delta -0.23 0.06 are shown as a function of time, with our observations as the point on the right hand side. Our results are in inner protractor of the eyepiece was recorded and later line with the other observations. adjusted to accommodate the rotation of the eyepiece by 180 degrees, since zero degrees on the eyepiece dif- Possible Companion? fered by either 90 or 270 degrees, depending upon the During the review of our paper, Kent Clark brought orientation of the eyepiece. to our attention a regular oscillation in the position an- gle and separation which could be an unseen compan- Comparison with Previous Observations ion. This can be clearly seen in Figures 2 and 3. This Brian Mason from the United States Naval Obser- should be investigated further by more precise instru- vatory kindly provided past observations of this double mentation. star. The first observation of this system was made in

Position Angle over Time

286.00 285.00 284.00 283.00 282.00 281.88 281.00 280.00

Position Angle (degrees) Angle Position 1884.31 1898.59 1902.73 1913.1 1959.19 1983.8 1991.73 2000.77 Time (Besselian Year)

Figure 2: Position angle over time of the WDS observational data.

Separation over Time

199.00 198.00 197.00 196.66 196.00 195.00 1884.31 1898.59 1902.73 1913.1 1959.19 1983.8 1991.73 2000.77

Separation (arc-seconds) Separation Time (Besselian Year)

Figure 3: Separation over time of the WDS observational data.

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Observing 75 Draco with a Manual Dobsonian Telescope

Conclusion field rotation. Also, estimating the separation of dou- Our observations compare favorably to other obser- bles stars as they cross the linear scale can be difficult. vations made in the past. Our average position angle On the other hand, their advantage is that they are was 281.9°, which is 0.2° different from the last obser- widely available and much lower cost than their motor- vation of the double star at 282.1°. For the separation, ized counterparts. If more people used manual Dob- the calculated result is 196.7ʺ, which is a 0.1ʺ differ- sonians for gathering data, they could make a substan- ence from the last reported result of 196.6ʺ in the tial contribution to science and science education. Washington Double Star Catalog. Acknowledgements The high north position of the star caused it to take We would like to thank Brian Mason for providing much longer to drift compared to other stars. When previous observations of this double star. We also ap- making measurements with manual telescopes, it can be preciate Russell Genet for lending us his astrometric useful to find a target star that is in the northern portion eyepiece and teaching the research seminar. Thanks to of the sky to make it easier to make separation meas- Kent Clark of the University of South Alabama who urements, but not too far north—otherwise it becomes pointed out the potential companion star. Finally, we time consuming to make position angle measurements. thank the external reviewers of this paper: Joseph Also, the further north the double star is, the greater the Carro, Thomas Frey, Russell Genet, Bobbie Johnson, field rotation will be between the measurements, and Vera Wallen, and Eric Weise. this could reduce the accuracy of the position angle measurements. References The goals of this research paper were met as we Argyle, R. W. Observing and Measuring Visual Dou- learned how to measure and calculate the position angle ble Stars. 2nd ed.: Springer, 2012. and separation of double stars. We also learned how to write a science paper and met the objective of determin- Mason, B. D., G. L. Wycoff, and W. I. Hartkopf. ing the current separation and position angle between "WDS 20282+8125 STH 7AC." Washington Dou- the two stars. The possibility of discovering a new ble Star Catalog. Web. 6 Nov. 2012. companion in the star system was an unexpected and http://ad.usno.navy.mil/wds/ exciting result. In closing we note that manual (non-tracking) Dob- sonians are alt-azimuth telescopes, and thus suffer from

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The Visual Triple Star ADS 16185 - STF2934

Henry Zirm

Markt Schwaben, Bavaria Germany

[email protected]

Abstract: In this article the visual triple star ADS 16185 - STF2934 is examined. In first studies by Heintz in 1962 and 1981 were reported a probably, up to now unresolved third star. As with similar visual multiple star systems like Zeta Aquarii or Zeta Cancri, a periodic “wobble” in the measurements of the apparent outer orbit (the visible components) is clearly visible. With the help of extensive, additional visual and speckle measurements from the past 30 years, an im- provement of the outer (visible component) and inner (invisible component) orbit was per- formed.

spectroscopically separated. Due to the relatively rapid Introduction variation in the radial velocity of the component A, the This system is located in Pegasus and was first ob- association of the inner orbit to component A is likely. served by H.G.W. Struve in 1830. Later, Heintz (1962) The radial velocity difference between component B was the first observer who held a third, unseen compan- and A defines the position of the ascending node. ion in this system very likely. Altogether, there are cur- rently only two complete orbit calculations for an inner Measurements preparation and assignation of and outer orbit, both investigations are from Heintz weights (1962, 1981). The observations used in this work mainly came Adopted from the SIMBAD database, the most from the Washington Double Star catalogue (WDS), relevant designations are: ADS 16185, STF2934, WDS obtained via email request by Brian D. Mason and his 22419+2126 AB, HIP 112063, HD 215013. colleagues. The component A and B has visual magnitudes 8.6 Before using any analytical method to calculate and 9.5 mag. The combined spectral class is G0, infor- orbital motion parameters,  was corrected for preces- mation regarding the luminosity class could not be sion. Furthermore  and  were plotted against time found. which allows for the detection of measures with impor- The recalculated Hipparcos trigonometric parallax tant errors or quadrant ambiguity. Measures with the is 11.35 ± 1.18 mas (van Leeuwen, 2007), this corre- largest errors, provided that these are recognizable as sponds to a distance of 88 ± 8 parsecs. Tokovin (2002; such, were assigned zero weight. 2008) published a series of radial velocities for both The initial weights for  and  measures were as- components. Thereby both components are measured signed using a the weighting scheme based on Hart-

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The Visual Triple Star ADS 16185 - STF2934

kopf, McAlister & Franz (1989), Mason, Douglass Hart- The relationship is described by: kopf (1999), Seymour et al. (2002) for the speckle meas- ures and Docobo & Ling (2003) for the visual measures. Aa( cosωΩ cos sin ωΩ sin cosi) The initial  weights were five times larger than  BB weights (Heintz 1978) for visual measures. Ba(cosωΩBB sin sin ω cos Ω cosi)

For the chosen orbital calculation, the transforma- Fa(sinωΩBB cos  cos ωΩ sin cosi) tion of  and  into Cartesian coordinates is necessary Ga(sinωΩ sin  cos ω cos Ω cosi) and follows the guidelines of Heintz (1978). The differ- BB ence of the measurement accuracy of the angle com- pared with measurement accuracy of the distance (for With the following formulae (Argyle 2004) one can the visual measurements) should also be considered in transform the Thiele-Innes elements into the Campbell determining the weights. With the help of a weighting elements: transformation, the advantage of this information will be applied. A good way to transform the weights for polar ABFG22 22 coordinates into weights for Cartesian coordinates was 2;uvAGBF described by van den Bos (1932) and will be here used: 2 au2  uvuv   1 sin 2 cos 2 1 cos 2 sin 2   and   m w w w w w w i  arccos2       a

After several iterations on the basis of a preliminary B  FBF orbit calculation process, the measures with residuals arctan arctan larger than 3σ were assigned zero weight. Later, the non ω  A GAG -zero weight measures were re-assigned following the 2 work of Irwin, Yang & Walker (1996). B  FBF Furthermore, to reduce the computational effort, I arctan arctan will calculate "normal points". Here I follow the guide- Ω  A GAG lines to Zirm (2011). 2

Method of Orbital calculation in general The remaining elements, the period P in years, the With direct reference to the method of Hartkopf, time of periastron passage T, the numerical eccentricity McAlister & Franz (1989)), if the three elements, the e are associated within the following formula; the Ke- period P (in years), the time of periastron passage T and pler equation: the numerical eccentricity e are known; the Thiele-Innes elements (A, B, F, G) can be calculated with a method 360 of least squares (on basis of a given set of observations) tTiiii M  Eesin E with the following formulas: P

Heintz (1978) recommends solving the Kepler's X cos Ee xAXFYiicos i  i  i ii  equation, the following iterative approximation method. yBXGYsin 2 ii i i  i YeEii1sin Six iterations are sufficient for obtaining the Eccentric

anomaly E: The geometrical elements, that is, the so-called e2 EMeMsin  sin 2 M Campbell-elements (the angular semi major axis (a), 0 2 inclination (i), position angle of the line of nodes (), MM and the angle between the node and periastron ()) are 0 MEeE00sin 0 EE 10  computed from the Thiele-Innes elements (in rectangu- 1cos eE0 lar brackets) by a "least square method".

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The Visual Triple Star ADS 16185 - STF2934

The initial parameter for P, T and e can be adopted Process to find the “best orbit” from a recently known orbit (in this case from Heintz The theoretical basis of the so called “three dimen- (1981)) to calculating initial values for E. On this basis, sional” grid search method follows according to Hart- it is now possible to calculate the theoretical positions kopf, McAlister, & Franz (1989): “… perform a “three and to match these with the observed positions of the dimensional” grid search in the vicinity of a set of input components. values of P, T, and e, in each grid step calculating the

xcalcAX FY y calc BX GY remaining elements and determining an overall resid- ual…”. AX FY   arctan Within reasonable limits of P, T, and e, one must calc BX GY now in preselected step sizes adjust the values for P, T, and e in order to obtain the set with the smallest residu- 22 2 calc AX FY BX GY als. In that case the value  /has to be minimized:

nn        ww  2  2 i obs calcii i  obs calc  2 iiii i   ii11  Calculation of the combined outer and inner or- 27n  bital motion, adoption for a triple star solution 2 The following indices are used: AB corresponds to The orbit with smallest  /value is the orbit with the outer system; Aa corresponds to the inner system. A minimum residuals and thus the “best orbit”. combined solution for the inner and outer orbital (sub) The calculation was carried out in Visual Basic motion can calculate the corresponding A, B, F, G val- (VBA), applied in Microsoft EXCEL2010. This VBA ues from the combined least square equation: code was kindly provided by my colleague Francisco Rica Romero. xiABABABABAaAaAaAa AX  FY  AX  FY Results of combined orbit calculation Starting from the recent elements of Heintz (1981), I yiABABABABAaAaAaAaBX  GY  BX  GY now attempt to find the orbit with the lowest residuals

by the variation of the dynamic elements P, T, and e. Here, different options have been tried. First, the orbital The residuals i and i are determining by the followed formulae: periods determined by Heintz were used to calculate preliminary circular orbits. The resulting elements a, i, XEeYeEcos  12 sin , and  (2nd column of table 1) were compared with AB ABi AB AB AB ABi the original elements of Heintz (1st column of table 1). 2 XEeYeEAacos Aai Aa Aa  1 Aa sin Aai Alone this preliminary calculation yielded a significant reduction of systematic deviations of Heintz orbits. The next step is the assumption of a circular orbit xAXFYAXFYcalci AB ABi AB ABi Aa Aai Aa Aai for the inner and outer system. Now, by alternating yBXGYBXGYcalci AB ABi AB ABi Aa Aai Aa Aai variation of Pinner and Pouter periods, it was searched for the orbital solutions with the lowest 2/. The resulting AX FY AX FY   arctan AB ABi AB ABi Aa Aai Aa Aai elements are written in the 3rd column of Table 1. Also calci BX GY BX GY AB ABi AB ABi Aa Aai Aa Aai here again a significant improvement can be obtained. 2 But still remained are significant and periodic residuals AXAB ABi FY AB ABi AX Aa Aai  FY Aa Aai   calci  that were identical with the period of the inner orbit. BX GY BX GY 2 AB ABi AB ABi Aa Aai Aa Aai Derived from this, the inner orbit seems to be eccentric. For a new "grid search" passageway, the outer orbit         is already assumed to be circular, and the inner orbit is i obs calcii i  obs calc  (Continued on page 218)

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The Visual Triple Star ADS 16185 - STF2934

Table 1: Collection of calculated orbits, corresponding residuals and masses

circular Heintz (1981) fixed Periods circular final inner outer orbit, original ele- from Heintz inner and and outer or- eccentric ments (1981) outer orbit bit inner orbit Orbital elements for the outer orbit AB P [yr] 636 636 747 739 3350 T [yr] 1769 (2087) 1764.8 1741.3 1740 1868.6 e 0 0 0 0 0.70 a ["] 1.46 1.48 1.71 1.70 3.78 i [°] 126.9 126.7 120.4 119.2 128.5  [°] 0 0 0 0 32.0 [°] 1 1 1 1 1 2000 207.1 (27.1) 210.4 206.9 207.8 185.5 Orbital elements for the inner orbit Aa P [yr] 82 82 79.3 81.8 81.0 T [yr] 2006 (1965) 2005 2001.08 1992.5 1992.3 e 0 0 0 0.42 0.47 a ["] 0.074 0.099 0.095 0.101 0.101 i [°] 42.2 45.8 50.9 55.5 58.4 [°] p 0 0 0 308.8 308.9 [°] 1 1 1 1 1 2000 193.8 (13.8) 210.3 194.9 198.2 199.3 Residuals: 2/, rms and MA 2/ 12.701 2.175 1.635 1.152 1.000 rms  [°] 1.52 0.97 0.85 0.74 0.67 rms  ["] 0.071 0.024 0.021 0.018 0.017 MA  [°] 1.28 0.71 0.58 0.43 0.40 MA  [“] 0.066 0.015 0.015 0.010 0.010 Total mass of the system

MAB 5.3 5.5 6.1 6.2 3.3 1. defined due the radial velocity difference adopted from Tokovinin (2002, 2008)

Figure 1: zoomed view of the final orbits and additionally the outer orbital path recently calculated by Heintz (1981). The scale is in arc seconds.

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The Visual Triple Star ADS 16185 - STF2934

(Continued from page 216) Table 2: Inner and outer orbit assumed to be eccentric. Thereby iterative Pouter is Ephemerides searched, then Pinner, Tinner and einner. This leads to an im-

provement of the residuals, supporting the assumption of t °2000 " an eccentric inner orbit. It is known that the assumption 2013.0 53.6 1.275 of a circular orbit is only a simplification, however the 2014.0 53.2 1.284 present measurements are not sufficient and cover only a small part of the orbital path and it is very difficult to 2015.0 52.9 1.294 calculate an eccentric orbit. Therefore the simplification 2016.0 52.5 1.303 using a circular orbit. 2017.0 52.2 1.313 This raises the question: are the present measure- 2018.0 51.8 1.323 ments sufficient to calculate a (probably) eccentric outer orbit? The alternating "grid search" variation of P, T, e 2019.0 51.5 1.333 for the outer and inner orbit, resulted in the "Final Or- 2020.0 51.2 1.343 bit" (Table 1, last column), displayed in a zoomed view 2025.0 49.7 1.395 in Figure 1. 2030.0 48.4 1.449 In principle the result seems to show a convergence to increasing period and eccentricity. However, since the 2035.0 47.2 1.504 improvement of the 2/ value, due the changes greater 2040.0 46.1 1.559 than e ~ 0.7 and P ~ 3500 years, is less than 1 per thou- 2045.0 45.1 1.614 sand and it can be terminated at this point. Therefore, 2050.0 44.2 1.668 the final orbital elements represent quite a good fit on the basis of the currently available measurements. The for providing a short-term measurement and his very ephemerides until to 2050 are tabulated in Table 2. helpful support, he generated the "grid search" algorithm in VBA code. I would like to thank Cliff Ashcraft for his Measurements and Residuals kind support for the correction of the English transla- Table 3 gives the historical measurements of tion. STF2934 as obtained from U.S.N.O. Washington Double This research has made use of the Washington Dou- Star catalogue WDS. Explanation of reference codes ble Star Catalog maintained at the U.S. Naval Observa- column 5 can be found on the USNO web site http:// tory, the NASA Astrophysics Data System Biblio- ad.usno.navy.mil/wds/request.html. The last two col- graphic Services and the SIMBAD database (operated at umns give the differences in position angle  and CDS, Strasbourg, France). separation  from the fitted orbit. References Summary Argyle, B., 2004, Observing and measuring visual In this work, final orbital elements for the outer and double stars, Patrick Moore's practical astronomy invisible inner orbit of ADS16185 were determined. A series. Berlin: Springer, ISBN: 1852335580 significant reduction of the residuals was obtained in Docobo, J. A.; Ling, J. F., 2003, A&A, 409, 989 comparison with previous and/or circular orbits. Unfor- tunately the outer orbit is still too uncertain to obtain a Hartkopf, W. I., McAlister, H. A., Franz, O. G., 1989, reliable total mass MAB (with correspondingly small AJ, 98, 1014 errors) for the whole system. It will be important that Heintz, W. D., 1978, Double Stars (revised edition), future observing sessions detect directly the invisible Dordrecht, D. Reidel Publishing Co. (Geophysics component. The outlook for the upcoming GAIA mis- and Astrophysics Monographs. Volume 15). sion generates hope for the absolute confirmation that ADS16185 is threefold. Heintz, W.D, 1962, VeMun, 5, 135H Heintz, W.D, 1981, ApJS, 45, 559H Acknowledgements I am particularly grateful to Francisco Rica Romero (Continued on page 220)

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The Visual Triple Star ADS 16185 - STF2934

Table 3: Normal point visual measurements

Date ° " N Reference ° " 1830.780 187.8 1.220 3 StF3 2.1 0.057 1843.420 176.7 1.196 3 Mad3 0.6 0.066 1856.870 168.2 1.100 2 Se_2 -1.1 -0.050 1865.870 166.0 1.110 5 D__4 Frr1 0.5 -0.034 1873.835 163.7 1.183 5 WS_4 Gld1 1.5 0.062 1874.840 162.0 1.150 3 WS_3 0.2 0.033 1879.875 158.8 0.879 8 Sbk2 Hod3 Smt3 -0.7 -0.213 1886.400 156.6 1.114 14 Eng7 dBl2 StH2 Hl_3 0.5 0.066 StH7 Cel2 Sp_8 Com6 Nst2 1891.410 153.0 1.008 27 -0.1 0.003 Glp2 L__1 Cls3 Dys1 Cow1 Bow4 1896.920 146.8 0.914 12 -2.1 -0.036 Bry2 Coh1 Bow10 L__3 Fay1 Hu_1 1901.900 142.6 0.907 19 -1.2 0.013 Pos1 Dob2 1906.915 136.7 0.831 7 Bow2 Frm1 Loh1 L__1 VBs2 0.0 -0.012 1911.200 129.7 0.760 14 Bow11 Wz_3 0.5 -0.059 1916.710 124.2 0.820 14 Dob5 Doo3 Com4 VBs2 3.1 -0.014 Btz5 Cha4 StG6 Dob1 Gcb1 1922.115 118.9 0.879 20 2.6 0.016 VBs3 StG6 B__3 Pav1 Plq1 Els4 1926.375 112.3 0.864 25 -1.1 -0.018 Cul1 Rab5 Fur4 Kui3 Dob2 Fen2 Ol_4 Smw9 1931.650 110.1 0.973 27 -0.3 0.073 Brt3 StG4 Rab14 Baz4 Ol_7 Smw3 Dur7 1936.955 107.9 0.890 39 0.4 -0.022 Dic4 1941.855 104.4 0.986 26 Scd2 Rab20 Vou3 Ard1 -0.4 0.066 1946.450 102.1 0.878 13 Dur4 Baz3 Nev1 Rab3 Ard2 0.0 -0.046 1952.420 97.8 0.895 33 VBs3 Rab20 Dom5 Ol_2 Dju3 -0.6 -0.032 Rab19 Cou6 Wor3 B__3 Dom2 1957.115 94.5 0.935 34 -0.6 0.005 Pau1 Dom2 Wor8 Hei19 VBs5 Sym4 1961.660 92.2 0.949 42 0.4 0.016 B__4 1967.110 86.8 0.921 8 Zul1 Pop1 Wor3 Hei3 -0.5 -0.019 1972.515 82.2 0.953 10 Zul2 Baz3 Wor4 Ole1 -0.2 -0.001 1977.205 77.9 0.953 23 Zul6 Hei9 Hln3 Wor3 Pop2 0.1 -0.021 Hei4 Zul13 Pop5 Wor4 Drd2 1981.925 72.6 1.017 35 -0.2 0.008 Mss4 LBu3 1986.170 68.5 1.023 17 Sca4 Wor3 Zul5 Lin3 Hei2 0.3 -0.034 1990.565 66.0 1.040 13 Zul5 Gii2 Pop1 Hei3 LBu2 2.1 -0.088 1995.940 61.5 1.198 5 Hei3 Alz2 0.9 -0.026 2000.350 58.9 1.253 8 Alz6 Lin1 Pri1 -0.6 -0.027 2006.360 57.0 1.323 3 Alz3 -1.4 -0.006 normal point speckle/CCD/Hipparcos measurements Date J° r" N Reference D J° D r" 1992.200 62.3 1.159 7 WSI6 HIP1 -0.3 0.000 1996.940 60.7 1.250 21 WSI10 Gii1 Mor10 0.4 0.012 2002.050 59.2 1.302 9 WSI8 Mor1 Slm1 0.0 0.006 2006.845 58.1 1.325 2 WSI1 Sca1 -0.2 -0.007 2011.525 57.6 1.358 4 Los2 Sca1 FMR1 0.1 -0.001

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The Visual Triple Star ADS 16185 - STF2934

(Continued from page 218) Irwin A. W., Yang S. L. S., Walker G. A. H., 1996, PASP, 108, 580 Mason, B. D., Douglass, G.G., Hartkopf, W. I., 1999, AJ, 117, 1023 Seymour, D. M., Mason, B. D., Hartkopf, W. I., Wy- coff, G. L., 2002, AJ, 123, 1023 Tokovinin, A. A.; Smekhov, M. G., 2002, A&A, 382, 118 Tokovinin, A., 2008, MNRAS, 389, 925 van Leeuwen, F. 2007, Hipparcos, the New Reduction of the Raw Data (New York: Springer) (data ob- tained from Simbad data base: I/311) van den Bos, W. H., 1932, CiUO, 86, 261 Zirm, H., 2011, JDSO, 7, 24

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POU 5641 (WDS 22077+2521). A Binary Composed of a Red dwarf and a White Dwarf

F. M. Rica

Double Star Section of Liga Iberoamericana de Astronomía (LIADA) Astronomical Society of Mérida [email protected]

Abstract: The Double Star Section of the LIADA have studied many long neglected double stars during 2006-2010. These yet unpublished results start to see the light with this article. The main aim of this work is present one of the more interesting long neglected pairs studied in the last years by our group: POU 5641 (= WDS 2207+2521). In the time of our study, it was only meas- ured in 1899. This pair is composed of common proper motion star (a K2V dwarf and a previ- ously known hot white dwarf) with 11.2 and 14.5 magnitudes at 58 parsecs of distance and sepa- rated by 7.89”. Astrophysical basic parameters were determined analyzing and consulting the data from the literature. Eight astrometric measures (position angles and angular distances) were performed using astrometric catalogs and photographic plates from public surveys. No signifi- cant relative velocity was detected. A dynamical study (comparing the relative velocity with the escape velocity) showed that POU 5641 likely is a gravitationally bound pair.

1. Introduction 2. Astrometric Observations When LIADA members measured and studied POU During the last years, the LIADA Double Star Sec- 5461 in 2008, it was an unconfirmed and neglected pair tion have measured and studied many neglected double only measured in 1899 by Pourteau. Recently the WDS stars. In the fourth observational program of 2008 we catalog has added 5 astrometric measures more, con- listed POU 5641 (= WDS 2207+2521), one of many firming this object. LIADA Double Star section per- unconfirmed and neglected double stars not resolved formed 8 astrometric measures spanning from the year since before 1900. Most of these double stars are pairs 1950 to 2008, a 58 year baseline. For this astrometric of unrelated stars, that is optical in nature, which have work, Digitized Sky Survey plates and astrometric cata- no astrophysical interest. But POU 5641, composed of logs (2MASS and AC2000) were used. In addition to stars with magnitude 11.2 and 14.5 separated by 7.9 arc this, one measure was performed using a CCD camera. seconds, surprised us not only for the physical relation Rafael Benavides, a well-known double star observer in of the stellar members, but also by the astrophysical Spain, used a 0.3 m telescope with an Atik 16HR CCD interest of the component stars. camera with an image scale of 0.995 arcsecond/pixel The organization of this paper is as follows. Sec- (see Figure 1). tions 2 and 3 presents the astrometric observations and Table 1 shows the relative astrometry (the epoch of the astrophysical characterization. The dynamic study is observation, the angular separation and distance, the detailed in Section 4. The conclusions are detailed in origin of the measure and the observer are listed) used Section 5. in this work.

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POU 5641 (WDS 22077+2521). A Binary Composed of a Red dwarf and a White Dwarf

Figure 1. WDS 22077+2521 = POU 5641. Taken by Rafael Benavides in 2008.760. Figure 2. POU5641. The position for the white dwarf is marked with an empty red circle.

3. Astrophysical study formed following basically the guidelines published in The astronomical literature was consulted searching Benavides et al. (2010) and Rica (2012). The interstellar for astrophysical data for the stellar components of POU reddening for this pair (galactic latitude of -24.4 deg) 56411. Table 2 lists the multiwavelengh photometric determined in this work was of E(B-V) = 0.02. data used in this work. The AVVSO Photometric All-Sky The primary component is a K5V star with a photo- Survey (APASS) catalog included in the UCAC4 astro- metric distance of 59 - 60 pc and with a significant metric catalog (Zacharias, et al. 2012) provides 5 optical proper motion. The UCAC3 and the PPMXL catalogs -1 bands and it is of great usefulness in our astrophysical list similar values ( = +88.4 ± 1.6 mas yr and  = -27.7 ± 1.6 mas yr-1). This data was confirmed in this work using plates from Digitized Sky Survey, and the Table 1. Relative Astrometry astrometry from the AC2000 catalog (epoch 1894.882) and 2MASS (epoch 1997.840). This is the first time that Epoch  [º]  ["] Origin Observer the spectral type (and the luminosity class) and the dis- 1950.609 239.45 8.133 DSS FMR tance are determined. The photo-metric data for the secondary component 1990.776 238.14 7.72 DSS FMR is very poor. The version of 2008 for the Spectroscopi- 1992.734 242.42 7.65 DSS FMR cally Identified White Dwarfs (McCook & Sion 1999) 1995.557 238.27 7.31 DSS FMR catalog lists a weak and hot white dwarf very near of the 1983.772 239.2 8.33 DSS AOG primary component with V band magnitude of 14.47 1991.231 237.9 7.96 DSS AOG (Table 2 lists more photometry data), a B-V color of 1997.84 240.2 7.99 2MASS AOG_2M -0.10 and an absolute magnitude in V-band of +10.77. 2008.760 239.7 7.99 CCD BVD While Green, Ali & Napiwotzki (2000) list a V band characterization. The good accuracy of the V band mag- magnitude of 14.58, an effective temperature of 26,129 nitude was confirmed consulting the ASAS catalog2 K and a mass of 0.74 solar mass. (Pojmanski 1997). The astrophysical study was per- Figure 2 shows the stellar members of POU 5641.

1The Aladin, VizieR and Simbad Virtual Observatory tools were 2All Star Atlas Catalogue, http://archive.princeton.edu/~asas/ used. 2All Star Atlas Catalogue, http://archive.princeton.edu/ asas_main.html

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POU 5641 (WDS 22077+2521). A Binary Composed of a Red dwarf and a White Dwarf

Table 2. Photometry

Passband A [mag] Ref. B [mag] Ref.

B 12.281±0.013 APASS 14.37 McCook & Sion (1999)

g 11.758±0.012 APASS ......

V 11.249±0.011 APASS 14.47 McCook & Sion (1999)

r 10.844±0.010 APASS 14.991±0.145 CMC14

i 10.610±0.041 APASS ......

J 9.067±0.023 2MASS 14.993±0.131

H 8.497±0.016 2MASS ......

K 8.343±0.018 2MASS ......

W1 8.246±0.023 WISE ......

W2 8.269±0.021 WISE ......

W3 8.161±0019 WISE ...... The position for the white dwarf is marked with an measures with respect the time. As is usual in this type empty red circle. But, what star is the white dwarf? The of neglected binaries, only a few poor-quality measure- weak magnitude for the white dwarf suggest me that ments can be used. The observational data only allows could be POU 5641 B or the weak star at East of the detecting relative motions greater than 3.0 mas yr-1. The primary component. This star has a V magnitude of relative motion measured (1.2 ± 3.0 mas yr-1) is smaller about 15.6 with JHK colors that matches with a medium than this limit and it is consistent with zero relative mo- -F star. POU 5461 B has a color rCMC – J2MASS = 0.0 tion. This result confirms the common proper motion for what is in agreement with the color listed for the white both stars. Literature no list proper motion for the secon- dwarf. If the V-J color is plotted in a reduced proper dary component. In this work, the proper motion was motion diagram, POU 5641 B is located in the white determined, for the first time, from the proper motion of dwarf region. Therefore, white dwarf nature for POU the primary component and the relative motion meas- 5461 B is confirmed. ured: There is an X-ray source very near of POU 5641.  = +89.6 ± 2.7 mas yr-1 Flemming et al. (1996) list the secondary component in  = -27.9 ± 2.6 mas yr-1 the “Catalogue of ROSAT White Dwarfs” as the optical counterpart for this X-ray source. There are two important pieces of evidence for the Are the stellar components for POU5641 two stars binarity of POU 5641: the common proper motion and at the same distance? From the absolute magnitude of the very similar photometric distances for both compo- the white dwarf, a photometric distance of about 55 pc nents. The astrometric observations do not yield a deter- (distance moduli of +3.77) was determined, in very good mination of a significant relative motion and velocity. agreement with the distance for the primary component The value for the relative velocity determined in this (about 59-60 pc and distance moduli of +3.94). There- work is 0.33 ± 0.81 km s-1 and is therefore consistent fore, the stellar components of POU 5641 surely are at with zero. The escape velocity for POU 5641 assuming the same distance. a face-on3 orbit is 2.38 km s-1 , therefore POU 5641 is Dynamical study likely a gravitationally bound system. The astrometric data listed in Table 1 were used to 3The calculation of the true escape velocity is not possible because determine the relative motion of secondary w.r.t. the the value of the radius vector ( r ) is unknown. Thus only the pro- jection of r (that is, the angular separation expressed in physical primary star, plotting the evolution of the astrometric units, called s) can be used. Like s ≤ r, the escape velocity calcu- lated is the upper value. When the orbit is face-on then s = r.

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POU 5641 (WDS 22077+2521). A Binary Composed of a Red dwarf and a White Dwarf

Conclusions Table 3. Astrometric and Dynamic Parameters POU 5641 (= WDS 2207+2521) is one of the most interesting pair against the long neglected pairs studied Table 3. Astrometric and Dynamic Parameters

by LIADA Double Star Section. This pair is composed Epoch 1998.503 of K2V and white dwarf (an X-ray source) stars with common proper motion and common distance with 11.2  (deg) 239.8 and 14.5 magnitudes at 58 parsec of distance and sepa-  (arcsec) 7.99 rated by a physical distance of 460 AU. We performed 8 x (AU).[E-W] -397 ± 79 astrometric measures spanning from the year 1950 to y (AU).[N-S] -231 ± 46

2008, that is, 58 years of time baseline. The dynamic -1 d/dt (mas yr ) -0.87 ± 2.47 analysis did not detect a significant relative motion and -1 -0.006 ± 0.018 velocity. See Table 3. Likely the relative motion is d/dt (deg yr ) -1 smaller than the escape velocity of the system and there- dx/dt (mas yr ).[E-W] 1.19 ± 2.13 fore POU 5641 surely be a gravitationally bound sys- dy/dt (mas yr-1).[N-S] -0.21 ± 2.06 tem. Vx (km s-1)…[E-W] 0.32 ± 0.58

-1 Acknowledgements Vy (km s )…[N-S] -0.06 ± 0.56 -1 This research has made use of the Washington Dou- Vz (km s ) ± ble Star Catalog maintained at the U.S. Naval Observa- Vxy (km s-1) 0.33 ± 0.81 tory. Vesc (km s-1) 2.38 ± This work made use of data products from the Two Mass A (Msun) 0.73 ± 0.07 Micron All Sky Survey, which is a joint project of the Mass B (Msun) 0.74 ± 0.07 University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, Distance (pc) 57.5 ± 11.5 funded by the National Aeronautics and Space Admini- stration and the National Science Foundation. References Benavides, R., Rica, F., Reina, E., Castellanos, J., Na- ves, R., Lahuerta, L., Lahuerta, S. 2010, JDSO, 6, 30. Fleming T. A., Snowden S. L., Pfeffermann E., Briel U., Greiner J., 1996, A&A, 316, 147. Green, P. J., Ali, B., Napiwotzki, R. 2000, ApJ, 540, 992. McCook G. P., Sion E. M., 1999, ApJS, 121, 1. Pojmanski, G., 1997, Acta Astronomica, 47, 467. Rica, F., 2012, JDSO, 8, 260. Zacharias N., Finch C.T., Girard T.M., Henden A., Bartlett J.L., Monet D.G., Zacharias M.I., 2012, AJ, (to be published).

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