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 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 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