Proper motions of cool and ultracool candidate members in the Upper Scorpius OB association

    Authors

    H. Bouy;E. L. Martin

    Comments

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    Abbreviated Journal Title

    Astron. Astrophys.

    Keywords

    stars: kinematics; stars: low-mass, brown dwarfs; open clusters and; associations: individual: Upper Scorpius; stars: formation; LOW-MASS STARS; T-TAURI STARS; BROWN DWARFS; SKY SURVEY; EVOLUTIONARY; MODELS; SIGMA-ORIONIS; MOVING GROUP; CLUSTER; MULTIPLICITY; OBJECTS; Astronomy & Astrophysics

    Abstract

    Aims. Proper motion measurements of the cool and ultracool populations in the Upper Scorpius OB association are crucial to confirm membership and to identify possible run-away objects. Methods. We cross-match samples of photometrically selected and spectroscopically confirmed cool and ultracool (K5 < SpT < M8.5) candidate members in the Upper Scorpius OB association using the literature and the USNO-B and the UCAC2 catalogues. 251 of these objects have a USNO-B and/or UCAC2 counterpart with proper motion measurements. Results. A significant fraction (19 objects, 7.6 +/- 1.8%) of spectroscopically confirmed young objects show discrepant proper motion. They must either belong to unidentified coincident foreground associations, or originate from neighboring star forming regions or have recently experienced dynamical interactions within the association. The observed accretor and disc frequencies are lower among outliers, but with only 19 objects it is unreliable to draw firm statistical conclusions. Finally, we note that transverse velocities of very low mass members are indistinguishable from those of low mass members within approximate to 4 km s(-1).

    Journal Title

    Astronomy & Astrophysics

    Volume

    504

    Issue/Number

    3

    Publication Date

    1-1-2009

    Document Type

    Article

    Language

    English

    First Page

    981

    Last Page

    U38

    WOS Identifier

    WOS:000270180600026

    ISSN

    0004-6361

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