AAS 204th Meeting, June 2004
Session 24 Protoplanetary Disks and the Brown Dwarf Desert
Oral, Monday, May 31, 2004, 2:00-3:30pm, 601

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[24.07] The Brown Dwarf Desert at 75-1200 AU

C. McCarthy (San Francisco State University), B. Zuckerman (U. C. Los Angeles)

We present results of a comprehensive infrared coronagraphic search for substellar companions to nearby stars. The research consisted of: 1.) a 178 star survey at Steward and Lick Observatories, with optical followup from Keck Observatory, capable of detecting companions with masses greater than 30 MJupiter, and semi-major axes between about 140 to 1200 AU. 2.) a 102 star survey using the Keck telescope, capable of detecting extrasolar brown dwarfs and planets typically more massive than 10 MJupiter, with semi-major axes between about 75 and 300 AU.

Only one brown dwarf companion was detected, and zero planets. The frequency of brown dwarf companions to G, K & M stars orbiting between 75 and 300 AU is measured to be 1±1%, the most precise measurement of this quantity to date. The frequency of massive (> 30MJupiter) brown dwarf companions at 120-1200 AU is found to be 0.7±.7%. The frequency of giant planet companions with masses between 5 and 10 MJupiter orbiting between 75 and 300 AU is measured here for the first time to be no more than ~ 3%.

Together with other surveys that encompass a wide range of orbital separations, these results imply that substellar objects with masses between 12 and 75 MJupiter form only rarely as companions to stars. Theories of star formation which could explain these data are only now beginning to emerge. We acknowledge support from NASA Astrobiology Institute.

If you would like more information about this abstract, please follow the link to http://tauceti.sfsu.edu/~chris/papers/nobds/. This link was provided by the author. When you follow it, you will leave the Web site for this meeting; to return, you should use the Back comand on your browser.

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