Title

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

Authors

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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