POSTER PAPER 2.03
Low-Mass Stars and Brown Dwarfs Around Sigma Orionis
M. J. Kenyon, R. D. Jeffries, T. Naylor
Institute: Department of Physics, Keele University, UK
Institute: School of Physics, University of Exeter, UK
Contact Email: mk@astro.keele.ac.uk
Abstract:
We present optical spectroscopy of 71 photometric candidate low-mass
members of the cluster associated with Sigma Orionis. Thirty-five
of these are found to pass the lithium test and hence are confirmed as
true cluster members, covering a mass range of < 0.055--0.3MSun,
assuming a mean cluster age of < 5 Myr. We find
evidence for an age spread on the (I, I-J) colour
magnitude diagram, members appearing to lie in the range 1-7 Myr. There are,
however, a significant fraction of candidates that are non-members, including
some previously identified as members based on photometry alone. We see some
evidence that the ratio of spectroscopically confirmed members to photometric
candidates decreases with brightness and mass. This highlights the importance
of spectroscopy in determining the true initial mass-function.
Index Keywords: Sigma Orionis; Sigma Ori; Spectroscopy
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Manuscript submitted: 2001-Sep-06
"The Future of Cool-Star Astrophysics", 2003, Eds. A. Brown,
G. M. Harper, & T. R. Ayres.
Proceedings of 12th Cambridge Workshop on Cool Stars, Stellar Systems,
& The Sun,
© 2003 University of Colorado.