arXiv:1901.09027v1 [astro-ph.SR] 25 Jan 2019 1 ed otedsoeyo rnisadtu,tedtcinof detection the thus, and transits of discovery the to stars of leads photometry the monitoring Observations Worley, 2018). & 2001, Douglass, Hartkopf, Double Wycoff, Washington (Mason, The Catalog in Star e.g. studied, published, been been have have binary they binaries detect and visual to of method number another large is A star systems. visible Astrome- one properties. only orbital of the try determine to order studied addition, in be detail In can in systems binaries. these visual measurements observed called astrometric be so using can as stars imaging both by systems, directly binary exo- of some detection the In for used planets. are Actually, as methods systems. same stellar the are multiple these or binary the for of methods several identification exist There our difficult. is in detection systems the such common ubiquity, of their very Despite Universe. are our systems and Galaxy stellar multiple or Binary Mexico GTO, Guanajuato, 36000 144, A.P. Guanajuato, de Universidad Astronomía, de Departamento Address Present [email protected] Email: . Jack, *D. Correspondence 2 1 catalogu Jack* D. velocity radial other with DR2 Gaia of derive comparison stars a candidate binary spectroscopic of catalogue A ARTICLE ORIGINAL xxx/xxxx DOI: 2018; X X Received abr,Hmug Germany Hamburg, Hamburg, Universität Sternwarte, Hamburger Mexico Guanajuato, Guanajuato, de Universidad Astronomía, de Departamento INTRODUCTION 1,2 eie 2018; X X Revised cetdXX2018 X X Accepted iais pcrsoi,ctlg,tcnqe:rda ve radial techniques: catalogs, spectroscopic, binaries: KEYWORDS: data. sta DR2 34,691 Gaia the of to total compared a when variations found velocity r we largest catalogue, the RAVE In stars. the candidate available, o SB1 catalogue 539 of velocity total radial a Pulkovo identified the with radia comparison show that a stars In 16 found we catalogue dwarf K-M the Comparin with curves. velocity v radial to using order systems in these orbits study stars these o of follow-up epochs different encourage at to spectra compiled stars, can 35,246 binary spectroscopic containing a present We (SB1). binar component spectroscopic ible possibly are stars these that tha goal indicate the with measurements, velocity per radial we the in stars, tions million catalogues velocity 7.2 radial existing about other with of comparison velocity radial mean the which of release data second Gaia published recently the Using cisn iayo utpesses hc edt aean have to need 90 to which close inclination systems, orbital multiple or binary eclipsing 04 rteCAACtlgo pcrsoi iayStars Binary Spectroscopic of Catalog CHARA the the al., like spectro- or et (Pourbaix 2004) parameters of Orbits Binary orbital catalogues Spectroscopic of their few Catalogue 9th and a systems exist com- binary invisible there scopic parame- the Also about orbital star. implications the panion provide veloc- of may radial about and the information ters of reveals spectroscopic analysis curve The single-lined only ity observed. a usually is and However, (SB1) visible (SB2). binary is can spectra stars component the both one of in lines observed spectral the cases be veloc- by some radial reveal In caused to variations. epochs requires star ity different at method a object this the of However, of spectra velocity orbit. its radial through the movement in changes of 2016). al., eclipsing et of (Kirk catalogue stars large binary very a in resulting mission Kepler nte ucsfldtcinmto stemeasurement the is method detection successful Another locities ◦ hshsbe civdwt the with achieved been has This . e tr ihol n vis- one only with stars ies nodrt erhfrvaria- for search to order in eetddffrne may differences detected t rf hi iaiyadto and binarity their erify h aaD2database DR2 Gaia the g da eoiycatalogue velocity adial nldsmeasurements includes srain obtaining bservations iaesascatalogue stars didate ipro tr we stars Hipparcos f omdasystematic a formed eoiyvariations. velocity l sta hwradial show that rs from d es 2 D. Jack
(Taylor, Harvin, & McAlister, 2003). Detecting a spectro- (Katz et al., 2018) obtained with the Gaia Radial Velocity scopic binary can either be pure luck or requires a survey at dif- Spectrometer (Cropper et al., 2018). While initially measure- ferent epochs like the Gaia-ESO Survey (Gilmore et al., 2012), ments for more than 9.8 million sources had been obtained, APOGEE (Majewski, APOGEE Team, & APOGEE-2 Team, after a selection process the final data release contains the 2016; Majewski et al., 2017) or LAMOST (Cui et al., 2012). radial velocities of about 7.2 million objects. During the selec- The rate of positive detections is for several reasons quite low tion process clear spectroscopic binary stars had been elimi- (≈ 10%) 1. One selection effect is that binary systems with nated, which will also lower the detection rate of our search. a low inclination are very hard to detect. In addition, long This was done for all stars that show a difference between the period binaries require a longer observational campaign and two components larger than 20 km s−1 (Sartoretti et al., 2018). some extreme eccentric orbits may show radial velocity varia- However, there will still be a very large amount of undiscov- tions only during a short part of the curve. The low detection ered spectroscopic binaries among the published data, which rate also comes from instrumental limitations, since the pre- usually show a somewhat larger error for the radial velocity cise determination of the radial velocity requires observations than do single stars. with high spectral resolution. For our comparison, we used three catalogues: the catalogue The Gaia mission (Gaia Collaboration et al., 2016) was for K-M dwarf stars of Sperauskas et al. (2016), the Pulkovo launched on December 19, 2013. It started observations in catalogue (Gontcharov, 2006) from Hipparcos stars and the July 2014, and the first data release was published on Septem- fifth data release (Kunder et al., 2017) of the RAVE survey. ber 14, 2016 with measurements of the position of more The first main obstacle is to correctly identify the stars than one billion stars, and in addition measurements of their of each of the catalogues with the respective source in the proper motions and parallaxes. Recently, Gaia published its Gaia DR2, since it does not come with a source identification second data release (Gaia Collaboration et al., 2018), which in other catalogues (like HD etc.) but only its proper source now includes measurements of the radial velocity of about 7.2 ids. However, there already exist two cross match lists of the million stars (Katz et al., 2018). These published values are Hipparcos2 and RAVE DR5 stars giving their most likely only mean values of several measurements of the radial veloc- neighbour in the Gaia DR2 database, which we make use of ity. Since Gaia DR2 is a very complete database, comparing in this work. For the stars of the K-M dwarf catalogue we the Gaia DR2 data with measurements of radial velocities at searched directly in the Gaia DR2 database for sources with different epochs published in other catalogues provides the radial velocity measurements within a few arcseconds around opportunity to find and identify possible SB1 stars. This will the position of the stars given in these catalogues. The size of allow a search for spectroscopic binaries and the measurement this search-window depends on the precision of the position of their radial velocity curves for orbit determination. in the catalogue since Gaia has, for obvious reasons, very pre- We compare the Gaia DR2 data with three other radial cise position measurements. For the K-M dwarf catalogue, we velocity catalogues. We describe our general method in some searched within a window of 10 arcseconds of the same posi- detail in Section 2. Section 3 contains the results of our com- tion, since the coordinates given in this catalogue are not very parison and a large catalogue of spectroscopic binary candidate precise. Because this catalogue is not very large, double or stars. A summary and our conclusions are presented in Section multiple identifications are revised by hand to assure the final 4. correct identification of the sources. The identification process results in a catalogue of a large number of stars with measured values for the radial velocity in 2 METHOD both the Gaia and the other catalogue respectively. Not all the sources of the other catalogues also have measurements in Gaia There exist several publications and catalogues with measure- DR2. The next step of our method is to check for variability in ments of the radial velocity of a large number of stars. In this the radial velocity measurements between the two catalogues. work, we compare the recent publication of the radial veloci- The selected radial velocity variation criterion depends on the ties of the Gaia data release 2 with the available data of three error of the radial velocity in each of the catalogues. We take a other catalogues. In this section, we briefly describe the gen- conservative value of a variation of more than three times the eral method that we applied in our search for spectroscopic respective error of the measured values in the catalogues. As binaries. a last step, we eliminate all photometric variable stars. Note The recently published Gaia DR2 for the first time contains that this general procedure may have to be adapted slightly measurements of the radial velocity of some of the sources for each of the three catalogues. Thus, we present the specific details in the next section where we also present the results of 1This is just a rough estimate for a random lucky search. The detection rate in this work is significantly lower due to selection effects. D. Jack 3
−1 the search, statistics, and details of the spectroscopic binary radial velocity of the K-M dwarf catalogue ( ̄vK−M in km s ) candidate stars. while the fourth column gives the number of individual obser- vations (N) used for the radial velocity determination. The fifth column contains all individual measurements of the radial −1 3 SPECTROSCOPIC BINARY velocity (vK−M in km s ), and the respective epochs are given CANDIDATE STARS in column six. The last column contains the measurements and errors of the radial velocity in the Gaia DR2 (vGaia in We applied the above described method to three different cata- km s−1). Since these are only a few spectroscopic binary can- logues of radial velocity measurements in order to identify the didate stars, we will briefly discuss each one of them in stars that show variations with respect to the radial velocities detail in APPENDIX A:. We also looked into the literature for reported in the Gaia DR2 catalogue. In this section, we explain additional publications of the radial velocity of these stars. in detail the results for each of the three catalogues and present We found that one star, namely HIP 19948, has already been the list of spectroscopic binary candidate stars. classified as a double or multiple star system in the SIMBAD database (Wenger et al., 2000). This star is actually the visual binary WDS J04167-1233AB listed in the Washington Double 3.1 Radial velocities of K-M dwarf stars Star Catalog (Mason et al., 2001, 2018) with a separation of The first catalogue that was compared with the Gaia DR2 was 2.5 arcseconds between the two components. With a variation the radial velocity catalogue of K-M dwarfs (Sperauskas et al., in the radial velocity of about 5.7 km s−1 and an error of the 2016). This catalogue contains radial velocity observations of Gaia DR2 measurement larger than 1 km s−1 the star could also 959 stars that are classified as K or M dwarf stars. Only stars be a spectroscopic binary. not suspected of having any radial velocity variations were selected, which will lower the expected detection rate of our search significantly. However, there is always the possibility 3.2 Pulkovo compilation of radial velocities that some spectroscopic binaries are still hidden in this cat- for Hipparcos stars catalogue alogue. We selected this recently published catalogue since The second catalogue that we compared with the Gaia DR2 it has a reasonable number of stars so that the small number radial velocity measurements is the Pulkovo compilation of of obtained spectroscopic binary star candidates can also be radial velocities for Hipparcos stars (Gontcharov, 2006) con- checked by hand. taining published radial velocity measurements of 35,495 Hip- We first performed an automatic identification procedure of parcos stars. The stars of this catalogue have different spectral the stars of the catalogue with the Gaia DR2 sources using a type and luminosity class but are located within a sphere of search-window of 10 arcseconds. Double or multiple identifi- 500 pc centered in the Sun having known parallaxes obtained cations were checked by hand, and photometric variable stars by Hipparcos (Perryman et al., 1997; van Leeuwen, 2007). were eliminated. We found that a total of 650 stars have been This catalogue is a compilation of radial velocities reported in clearly observed in both catalogues. The radial velocity mea- 203 publications. The median accuracy is roughly 0.7 km s−1, surements of the K-M dwarf catalogue have relatively small but some measurements have errors of up to 5 km s−1. −1 errors of about ≈ 0.5 kms . Therefore, we checked for radial We used the Hipparcos2 - Gaia DR2 cross match list to −1 velocity differences of more than 4 km s between the two cat- check for Gaia DR2 sources that have radial velocity measure- alogues to take into account the errors in both the K-M dwarf ment in both catalogues and obtained a final list of 16,601 stars. and the Gaia DR2 catalogues and a probable offset between the In the next step, we searched for variations in the radial veloc- catalogues. After applying this criterion, we obtained a list of ity and selected all stars that showed a difference of more than 16 stars that show radial velocity variations. This small num- three times the individual error of the Pulkovo value, but at ber clearly indicates that the K-M dwarf catalogue has mostly least 5 km s−1 to include errors of the Gaia DR2 radial veloc- stars that do not show radial velocity variations. The detection ity determination and systematic differences between the two rate of suspected SB1 stars in this catalogue is just 2.46 %. catalogues. Using this criterion we compiled a final list con- taining a total of 743 stars showing radial velocity variations of at least the mentioned threshold. This list of 743 Hipparcos stars was checked with the In Table 1 , we present the list of 16 stars that show radial −1 SIMBAD database, and we found that some stars have velocity variations of more than 4 km s . The table is sorted by already been identified as spectroscopic binaries while right ascension coordinate as in the K-M dwarf catalogue. The others are known photometric variable stars. Variability second column gives the magnitude in the V -band reported in the SIMBAD database. The third column gives the mean 4 D. Jack
TABLE 1 List of stars of the K-M dwarf catalogue that show a variation of more than 4 km s−1 in the radial velocity measurement when compared to the values of the Gaia DR2 database.
−1 −1 −1 Star mV ̄vK−M (km s ) N vK−M (km s ) EpochK−M (MJD) vGaia (km s ) GJ9038B 9.85 −0.7±0.3 6 −2.2±1.1 2455476.536 −4.75±0.84 −0.5±0.6 2455478.474 −0.7±0.6 2455479.449 −1.0±0.7 2455482.464 0.4±0.9 2455484.461 −0.9±0.9 2456681.221 HIP14165 11.792 21.8±0.7 1 21.8±0.7 2452930.914 33.82±7.03 HIP14593 10.06 28.2±1.2 1 28.2±1.2 2452928.894 15.93±0.48 HIP19948 10.901 48.0±0.8 1 48.0±0.8 2452330.632 42.26±1.12 HIP34361 11.081 −16.8±0.7 1 −16.8±0.7 2452328.721 26.98±0.35 HIP40724 9.868 88.1±1.0 2 89.2±1.0 2455881.616 81.9±1.87 87.1±1.0 2456679.455 TYC1379-91-1 11.63 29.4±0.4 4 30.0±0.7 2455271.365 −24.26±0.69 29.3±0.7 2455278.320 28.6±0.9 2455302.275 29.5±0.8 2455969.495 HIP44109 10.360 26.9±0.5 1 26.9±0.5 2455618.402 22.6±6.86 HIP46662 10.09 −51.3±0.3 3 −50.8±0.5 2451622.728 −45.22±1.24 −51.3±0.5 2455266.372 −51.7±0.5 2455655.361 HIP49969 10.629 25.9±0.6 2 26.1±0.8 2455621.430 31.59±1.28 25.7±0.8 2455655.323 HIP58099 10.5 −19.0±0.5 2 −18.7±0.7 2455610.611 −14.88±0.8 −19.2±0.6 2455655.508 HIP59000 10.016 −8.2±0.4 1 −8.2±0.4 2452328.912 −29.16±13.6 TYC 4558-1019-1 10.97 −102.0±0.3 3 −101.6±0.4 2452349.524 −19.22±1.54 −102.3±0.5 2455352.364 −102.5±0.5 2455622.566 GJ4327 12.07 13.4±1.2 2 14.0±0.9 2452927.796 −6.68±2.23 11.0±1.8 2455445.571 HIP115004 9.75 26.6±0.4 3 27.1±0.4 2455497.350 19.13±0.87 26.7±0.4 2455777.538 25.5±0.5 2455836.444 HIP116936 10.293 17.7±0.3 3 17.0±0.8 2455473.467 28.43±2.37 18.1±0.6 2455853.374 17.6±0.6 2455881.275 can also have an effect on variations of the radial veloc- measurements. In this list we found 72 stars with a radial ity of stars. We eliminated these stars from our catalogue velocity difference of more than 50 km s−1, and 42 stars show to obtain the final list of 539 stars, which is presented in a variation of more than 100 km s−1 between the two cata- the large Table B1 that can be found in APPENDIX B: logues. The largest variation was found for the star HIP 85690 and is also available online as a CSV file on the website that shows a difference in the radial velocity of 253.17 km s−1. http://www.astro.ugto.mx/~dennis/binary_candidates/.A histogram of the radial velocity differences between The first column gives the Hipparcos (HIP) number of the star the Pulkovo and the Gaia DR2 catalogues is presented in and the second column the difference in the radial velocity Figure 1 . There exists a small overdensity in the range of 100 (in km s−1) between the Pulkovo and the Gaia DR2 catalogue D. Jack 5
Pulkovo vs. Gaia DR2 Δ Δ Δ Δ 0000
200 00