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J/MNRAS/472/675      Wide binaries in Tycho-Gaia: search method (Andrews+, 2017)

Wide binaries in Tycho-Gaia: Search method and the distribution of orbital separations. Andrews J.J., Chaname J., Agueros M.A. <Mon. Not. R. Astron. Soc. 472, 675-699 (2017)> =2017MNRAS.472..675A (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Positional data ; Parallaxes, trigonometric Keywords: astrometry - parallaxes - proper motions - binaries: visual Abstract: We mine the Tycho-Gaia astrometric solution (TGAS) catalogue for wide stellar binaries by matching positions, proper motions and astrometric parallaxes. We separate genuine binaries from unassociated stellar pairs through a Bayesian formulation that includes correlated uncertainties in the proper motions and parallaxes. Rather than relying on assumptions about the structure of the Galaxy, we calculate Bayesian priors and likelihoods based on the nature of Keplerian orbits and the TGAS catalogue itself. We calibrate our method using radial velocity measurements and obtain 7108 high-confidence candidate wide binaries with projected separations s≲1pc. The normalization of this distribution suggests that at least 0.7 per cent of TGAS stars have an associated, distant TGAS companion in a wide binary. We demonstrate that Gaia's astrometry is precise enough that it can detect projected orbital velocities in wide binaries with orbital periods as large as 106yr. For pairs with s≲4x104au, characterization of random alignments indicates our contamination to be 5-10 per cent. For s≲5x103au, our distribution is consistent with Opik's law. At larger separations, the distribution is steeper and consistent with a power-law P(s)∝s-1.6; there is no evidence in our data of any bimodality in this distribution for s≲1pc. Using radial velocities, we demonstrate that at large separations, i.e. of order s∼1pc and beyond, any potential sample of genuine wide binaries in TGAS cannot be easily distinguished from ionized former wide binaries, moving groups or contamination from randomly aligned stars. Description: Our catalogue of wide binaries identified in the Tycho-Gaia Astrometric Solution catalogue. The Gaia source IDs, Tycho IDs, astrometry, posterior probabilities for both the log-flat prior and power-law prior models, and angular separation are presented. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 197 7108 Catalogue of wide binaries in Tycho-Gaia
See also: I/337 : Gaia DR1 (Gaia Collaboration, 2016) Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 19 I19 --- Gaia-ID1 Gaia ID for primary 21- 31 A11 --- TYC-ID1 Tycho ID for primary 33- 45 F13.9 deg RAdeg1 Right ascension (ICRS) at epoch 2015.0 for primary 47- 59 F13.9 deg DEdeg1 Declination (ICRS) at epoch 2015.0 for primary 61- 69 F9.3 mas/yr pmRA1 Proper motion (RA part) for primary 71- 78 F8.3 mas/yr pmDE1 Proper motion (DE part) for primary 80- 86 F7.3 mas plx1 Parallax for primary 88-106 I19 --- Gaia-ID2 Gaia ID for secondary 108-118 A11 --- TYC-ID2 Tycho ID for secondary 120-132 F13.9 deg RAdeg2 Right ascension (ICRS) at epoch 2015.0 for secondary 134-146 F13.9 deg DEdeg2 Declination (ICRS) at epoch 2015.0 for secondary 148-156 F9.3 mas/yr pmRA2 Proper motion (RA part) for secondary 158-165 F8.3 mas/yr pmDE2 Proper motion (DE part) for secondary 167-173 F7.3 mas plx2 Parallax for secondary 175-181 F7.5 --- P(logflat) [0/1] Posterior probability of a genuine binary using the log-flat prior (1) 183-189 F7.5 --- P(powerlaw) [0/1] Posterior probability of a genuine binary using the power-law prior (1) 191-197 F7.2 arcsec Sep Angular separation of pair
Note (1): Two separate posterior probabilities for each pair being a genuine binary are provided, depending on whether they are generated using a log-flat prior or a power-law prior. In many cases these probabilities disagree. See Section 7.4 for a discussion about how to use this catalogue.
Acknowledgements: Jeff J. Andrews, andrews(at)
(End) Jeff J. Andrews [U. of Crete], Patricia Vannier [CDS] 20-Nov-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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