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J/AJ/153/257                Comoving stars in Gaia DR1               (Oh+, 2017)

Comoving stars in Gaia DR1: an abundance of very wide separation comoving pairs. Oh S., Price-Whelan A.M., Hogg D.W., Morton T.D., Spergel D.N. <Astron. J., 153, 257-257 (2017)> =2017AJ....153..257O (SIMBAD/NED BibCode)
ADC_Keywords: Associations, stellar ; Stars, double and multiple Keywords: binaries: visual - methods: statistical - open clusters and associations: general - parallaxes - proper motions - stars: formation Abstract: The primary sample of the Gaia Data Release 1 is the Tycho-Gaia Astrometric Solution (TGAS): ≃2 million Tycho-2 sources with improved parallaxes and proper motions relative to the initial catalog. This increased astrometric precision presents an opportunity to find new binary stars and moving groups. We search for high-confidence comoving pairs of stars in TGAS by identifying pairs of stars consistent with having the same 3D velocity using a marginalized likelihood ratio test to discriminate candidate comoving pairs from the field population. Although we perform some visualizations using (bias-corrected) inverse parallax as a point estimate of distance, the likelihood ratio is computed with a probabilistic model that includes the covariances of parallax and proper motions and marginalizes the (unknown) true distances and 3D velocities of the stars. We find 13085 comoving star pairs among 10606 unique stars with separations as large as 10pc (our search limit). Some of these pairs form larger groups through mutual comoving neighbors: many of these pair networks correspond to known open clusters and OB associations, but we also report the discovery of several new comoving groups. Most surprisingly, we find a large number of very wide (>1pc) separation comoving star pairs, the number of which increases with increasing separation and cannot be explained purely by false-positive contamination. Our key result is a catalog of high-confidence comoving pairs of stars in TGAS. We discuss the utility of this catalog for making dynamical inferences about the Galaxy, testing stellar atmosphere models, and validating chemical abundance measurements. Description: The primary data set used in this article is the Tycho-Gaia Astrometric Solution (TGAS), released as a part of Data Release 1 (DR1) of the Gaia mission (Gaia Collaboration et al. 2016, Cat. I/337; Lindegren et al. 2016A&A...595A...4L). File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1a.dat 151 10606 Candidate co-moving pairs catalog: star table1b.dat 42 13058 Candidate co-moving pairs catalog: pair table1c.dat 38 4555 Candidate co-moving pairs catalog: group
See also: III/279 : RAVE 5th data release (Kunder+, 2017) I/337 : Gaia DR1 (Gaia Collaboration, 2016) I/259 : The Tycho-2 Catalogue (Hog+ 2000) I/239 : The Hipparcos and Tycho Catalogues (ESA 1997) Byte-by-byte Description of file: table1a.dat
Bytes Format Units Label Explanations
1- 5 I5 --- Star [0/10605]? Zero-based row index 7- 25 I19 --- Gaia Unique source identifier from the Tycho-Gaia Astrometric Solution (TGAS) 27- 29 A3 --- --- [TYC] 31- 41 A11 --- TYC Tycho-2 identifier (Hog et al. 2000, Cat. I/259) 43- 45 A3 --- --- [HIP] 47- 52 I6 --- HIP ? Hipparcos identifier (Cat. I/239) 54- 63 F10.6 deg RAdeg Right Ascension in decimal degrees (J2000) (1) 65- 74 F10.6 deg DEdeg Declination in decimal degrees (J2000) (1) 76- 83 F8.4 mas plx [2/286.4] Parallax 85- 91 F7.3 pc Dist [3.49/519.84] Distance 93- 98 F6.3 mag Gmag [4.8/12.6] Gaia G-band magnitude 100-105 F6.3 mag Jmag [3.29/11.58]? 2MASS J band magnitude 107-127 A21 --- RAVE Unique identifier of the Radial Velocity Experiment (RAVE) match (2) 129-135 F7.2 km/s RV [-889.49/763.91]? Radial velocity from RAVE (2) 137-142 F6.2 km/s e_RV [0.48/101]? Uncertainty of RV (2) 144-147 I4 --- Group [0/4554]? Identifier of the group this star belongs to 149-151 I3 --- Size [2/151] Size of the group this star belongs to
Note (1): From the Tycho-Gaia Astrometric Solution (TGAS; see Gaia DR1 in Gaia Collaboration 2016, Cat. I/337). Note (2): See RAVE 5th data release in Kunder et al. 2017 (Cat. III/279).
Byte-by-byte Description of file: table1b.dat
Bytes Format Units Label Explanations
1- 5 I5 --- Star1 [0/10597]? Star 1 zero-based row index 7- 11 I5 --- Star2 [9/10605] Star 2 zero-based row index 13- 20 F8.3 arcmin ASep [0.034/3399.65] Angular separation 22- 27 F6.3 pc PSep [0.005/10] Physical separation 29- 33 F5.2 [-] LR [6/12.66] Likelihood ratio, natural logarithm ln(L1/L2) (1) 35- 38 I4 --- Group [0/4554]? Identifier of the group the pair belongs to 40- 42 I3 --- Size [2/151] Size of the group the pair belongs to
Note (1): See Equations (8) and (9) in the paper.
Byte-by-byte Description of file: table1c.dat
Bytes Format Units Label Explanations
1- 4 I4 --- Group [0/4554]? Unique group identifier 6- 8 I3 --- Size [2/151] Number of stars in a group 10- 19 F10.6 deg <RAdeg> Mean Right Ascension of group members in decimal degrees (J2000) 21- 30 F10.6 deg <DEdeg> Mean Declination of group members in decimal degrees (J2000) 32- 38 F7.3 pc <Dist> [3.5/517] Mean distance of members
History: From electronic version of the journal
(End) Prepared by [AAS]; Sylvain Guehenneux [CDS] 11-Aug-2017
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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