Dahm, Scott

Contact Email: dahm@ifa.hawaii.edu
Institute: Institute for Astronomy, University of Hawaii
First Coauthor: E. L. Martin
Institute: Institute for Astronomy, University of Hawaii
Subject Area: Brown Dwarfs & Extrasolar Planets
Waveband: Optical
Technique: Imaging (Direct)
Presentation: Poster Display
Title: The First Resolved Brown Dwarf Binaries in the Pleiades
Abstract: We present initial results of an HST WFPC-2 photometric survey of selected very low-mass stars and brown dwarf candidates in the Pleiades open cluster. With a sample size of 16 objects, three are resolved as binaries with separations of less than 15 AU for an assumed distance of 125 pc to the cluster. Of these three candidates, CFHT-PL-19 was assessed as a non-member by the proper motion survey of Moraux, Bouvier and Stauffer (2001). The remaining two binaries are members based upon their proper motions or the presence of lithium in their spectra. These results complement those of Martin et al. (2000) in which an HST NICMOS and CFHT adaptive optics survey of 34 Pleiades members found no resolved pairs with separations greater than 27 AU. Combining the new observations with those of Martin et al. (2000), we derive a binary frequency and period distribution for brown dwarfs in the Pleiades. The results are compared with those of Duquennoy and Mayor (1991) for nearby solar-type stars, Fischer and Marcy (1992) for M dwarfs within 20 pc and Reid and Gizis (1997) for low-mass stars in the Hyades. We find a paucity of wide binary systems with separations greater than 15 AU (P 184 yr), however, close binaries with separations of less than 15 AU appear to be frequent.