Additional TWA members?

Free access article

Issue		A&A Volume 385, Number 3, April III 2002


Page(s)		862 - 866
Section		Stellar clusters and associations
DOI		http://dx.doi.org/10.1051/0004-6361:20020159

A&A 385, 862-866 (2002)
DOI: 10.1051/0004-6361:20020159

Spectroscopic verification of kinematically selected TWA candidates

I. Song¹, M. S. Bessell² and B. Zuckerman¹

¹ Department of Physics and Astronomy (UCLA), Los Angeles, CA 90095-1562, USA
² Research School of Astronomy and Astrophysics, The Australian National University, ACT 2611, Australia

(Received 27 September 2001 / Accepted 24 January 2002)

Abstract
We present spectroscopic measurements of the 23 new candidate members of the TW Hydrae Association from Makarov & Fabricius (2001). Based on H $\alpha$ and Li 6708 Å strengths together with location on a color-magnitude diagram for Hipparcos TWA candidates, we found only three possible new members (TYC 7760-0835-1, TYC 8238-1462-1, and TYC 8234-2856-1) in addition to the already known member, TWA 19. This eliminated most of the candidates more distant than 100 pc. Three Tycho stars, almost certainly members of the Lower Centaurus Crux association, are the most distant members of the TWA. A claim of isotropic expansion of TWA has to be re-evaluated based on our new results. Generally, one cannot identify new members of a diffuse nearby stellar group based solely on kinematic data. To eliminate interlopers with similar kinematics, spectroscopic verification is essential.

Key words: galaxy: open clusters and associations: individual: TWA -- stars: kinematics -- stars: planetary systems -- techniques: spectroscopic

Offprint request: I. Song, song@astro.ucla.edu

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