Comoving Stars in Gaia DR1: An Abundance of Very Wide Separation Comoving Pairs

Semyeong Oh, Adrian M. Price-Whelan, David W. Hogg, Timothy D. Morton, David N. Spergel

    Research output: Contribution to journalArticle

    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 13,085 comoving star pairs among 10,606 unique stars with separations as large as 10 pc (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 (pc) 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.

    Original languageEnglish (US)
    Article number257
    JournalAstronomical Journal
    Volume153
    Issue number6
    DOIs
    StatePublished - Jun 1 2017

    Fingerprint

    stars
    catalogs
    likelihood ratio
    parallax
    proper motion
    visualization
    confidence
    atmosphere
    stellar atmospheres
    open clusters
    binary stars
    inference
    contamination
    galaxies
    estimates
    chemical
    test

    Keywords

    • binaries: visual
    • methods: statistical
    • open clusters and associations: general
    • parallaxes
    • proper motions
    • stars: formation

    ASJC Scopus subject areas

    • Astronomy and Astrophysics
    • Space and Planetary Science

    Cite this

    Oh, S., Price-Whelan, A. M., Hogg, D. W., Morton, T. D., & Spergel, D. N. (2017). Comoving Stars in Gaia DR1: An Abundance of Very Wide Separation Comoving Pairs. Astronomical Journal, 153(6), [257]. https://doi.org/10.3847/1538-3881/aa6ffd

    Comoving Stars in Gaia DR1 : An Abundance of Very Wide Separation Comoving Pairs. / Oh, Semyeong; Price-Whelan, Adrian M.; Hogg, David W.; Morton, Timothy D.; Spergel, David N.

    In: Astronomical Journal, Vol. 153, No. 6, 257, 01.06.2017.

    Research output: Contribution to journalArticle

    Oh, S, Price-Whelan, AM, Hogg, DW, Morton, TD & Spergel, DN 2017, 'Comoving Stars in Gaia DR1: An Abundance of Very Wide Separation Comoving Pairs', Astronomical Journal, vol. 153, no. 6, 257. https://doi.org/10.3847/1538-3881/aa6ffd
    Oh, Semyeong ; Price-Whelan, Adrian M. ; Hogg, David W. ; Morton, Timothy D. ; Spergel, David N. / Comoving Stars in Gaia DR1 : An Abundance of Very Wide Separation Comoving Pairs. In: Astronomical Journal. 2017 ; Vol. 153, No. 6.
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