AAS 201st Meeting, January, 2003
Session 46. Planetary Systems: Observations and Models
Poster, Tuesday, January 7, 2003, 9:20am-6:30pm, Exhibit Hall AB

## [46.08] X-Rays From Brown Dwarfs In The \sigma Orionis Cluster

N. Adams, S. Wolk (Harvard-Smithsonian CfA), F. M. Walter (SUNY-SB), R. Jeffries (Keele), T. Naylor (U. of Exeter)

We have recently made a deep Chandra X--Ray Observatory observation of the young star forming region around \sigma Orionis. The goal of this HRC-I observation is to detect X--ray emission from young brown dwarfs (BDs) which have been discovered there. Detections of BDs by Chandra have been somewhat mixed with about 60 total published detections. This is, in part, because the detector of choice for clusters, ACIS-I, has very low effective area where BDs are brightest in X--rays, below 400 eV. The \sigma Ori cluster is uniquely suited to this study: it spans different stellar interior conditions (nearly 3 orders of magnitude in mass), it is relatively close and almost dust free (5% that of the ONC), its age is such that it has a good mix of stars with and without disks, and we have measured its mass function to well below the BD limit.

This work is supported by the Chandra X-ray Center NASA Contract NAS8-39073 and by Chandra guest observer grant G02-3019A.

Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.