EDP Sciences
Free access
Volume 367, Number 1, February III 2001
Page(s) 211 - 217
Section Formation, structure and evolution of stars
DOI http://dx.doi.org/10.1051/0004-6361:20000414

A&A 367, 211-217 (2001)
DOI: 10.1051/0004-6361:20000414

Proper motion of very low mass stars and brown dwarfs in the Pleiades cluster

E. Moraux1, J. Bouvier1 and J. R. Stauffer2

1  Laboratoire d'Astrophysique, Observatoire de Grenoble, Université Joseph Fourier, BP 53, 38041 Grenoble Cedex 9, France
2  SIRTF Science Center, Caltech, Pasadena, CA 91125, USA

(Received 16 November 2000 / Accepted 30 November 2000)

We report proper motion measurements for 25 very-low mass (VLM) star and brown dwarf (BD) candidates of the Ple iades cluster previously identified by Bouvier et al. (1998). Proper motions are measured with an accuracy of 9 mas/yr, compared to an expected tangential motion of about 50 mas/yr for Pleiades members. Of the 25 candidates, 15 have a membership probability of 95% or more and 7 are rejected as being field dwarfs. The 3 remaining candidates exhibit independent evidence for membership (lithium absorption or long-term proper motion). From the firm identification of Pleiades VLM and BD members, the cluster's substellar mass function is revised to ${\rm d}N/{\rm d}M\propto M^{-0.5}$ in the mass range from 0.04 to 0.3 $M_\odot$.

Key words: stars: low-mass, brown dwarfs -- stars: luminosity function, mass function -- Galaxy: open clusters and associations: individual: Pleiades

Offprint request: E. Moraux, moraux@laog.obs.ujf-grenoble.fr

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