AAS 197, January 2001
Session 52. Science with Adaptive Optics
Display, Tuesday, January 9, 2001, 9:30am-7:00pm, Exhibit Hall

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[52.03] Resolving Low-Mass Companions to G-type stars - Two Stars and a Binary Brown Dwarf

P.J. Lowrance, E.E. Becklin (UCLA Division of Astronomy), G. Schneider (Univ. of Ariz.), NICMOS IDT/EONS Team, STIS/8176 Team

Several candidate companions were discovered in our coronagraphic survey of nearby, young stars with the Near-Infrared Camera and Multi-Object Spectrometer (NICMOS) on the Hubble Space Telescope (HST). Discovery and characterization of low mass stellar and sub-stellar objects is fundamental to observational astrophysics, especially in related areas such as stellar evolution, the stellar mass function, and the origins of stellar and planetary systems. Substellar objects are predicted to be more luminous when younger, and therefore easier to detect.

We have recently acquired follow-up spectroscopic observations with the Space Telescope Imaging Spectrograph (STIS) and astrometric observations using adaptive optics on the Canada-French-Hawaii and Hale 200-inch Telescopes which provide supporting evidence that three of our candidates are indeed bona-fide companions. Based on evolutionary models, the proper motion companions to the G-type stars Gl 503.2 and HD 102982 are very low-mass stars, and the companions to Gl 577 likely form a brown dwarf binary. A dynamical determination of the mass of the close (sep ~ few AU) binary components of the brown dwarf secondary (Gl 577 B/C) will be possible within only the next few years.

This work is supported in part by NASA grants NAG 5-4688 to UCLA and NAG 5-3042 to the University of Arizona Instrument Definition Team. This talk is based on observations under grant GO-8176.01-97A with the NASA/ESA Hubble Space Telescope at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555.

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