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Session 80 - Star Clusters in the Milky Way.
Display session, Friday, January 09
Exhibit Hall,
We have conducted an extensive photometric search for brown dwarf candidates in the young, nearby open cluster IC 2391. Twenty-four objects in this survey have been identified as candidate brown dwarfs on the basis of their VRI colors and magnitudes. The IC 2391 open cluster is an ideal region in which to search for brown dwarfs. With a cluster age estimated to be approximately 30 million years, brown dwarf members will still be in the early, more luminous, stage of their evolution. We have made photometric VRI measurements of 21 CCD fields, each approximately 14x14 arcminutes in size, totalling an area of 1 square degree on the sky. Photometry for some 11,000 stars ranging in brightness from V=10 to V=20 were extracted from these images. Although the vast majority of these stars proved to be field stars (i.e., background or foreground to the cluster), several dozen objects were identified as potential members of the IC 2391 cluster based on their positions in the V/V-I color-magnitude and V-R/R-I color-color diagrams. Of these objects, two dozen were identified as candidate IC 2391 brown dwarfs based on theoretical predictions for brown dwarf temperatures and luminosities at an age of 30 million years. Ultimately, near-infrared photometry and spectroscopy will be needed in order to confirm whether or not any of these candidates are truly brown dwarfs. In addition to our brown dwarf candidates, we also identified 8 very blue (V-I < -0.3), apparently nearby objects which we believe are white dwarfs.
