AAS 195th Meeting, January 2000
Session 78. Young Stars, Disks and Planets
Display, Friday, January 14, 2000, 9:20am-6:30pm, Grand Hall

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[78.13] The Planetary Debris System in TWA 4 (HD98800)

F.J. Low, D.C. Hines, G. Schneider (Steward Observatory)

High fidelity NICMOS observations combined with WFPC2 and ground-based 4.7\mum photometry have enabled us to precisely determine the spectral energy distributions (SEDs) for the principal stellar components (A & B) in HD98800. The third major component, an extensive planetary debris system (PDS), emits more than 20% of the luminosity of B in a nearly perfect 165K blackbody SED, and orbits B at 4.5 AU (4 sub-stepped NICMOS camera 1 pixels). Despite this large covering factor and radial extent, a preliminary upper limit of only 6% is obtained for the ratio of reflected light to the total from B at 0.95\mum. These properties are similar to the zodiacal dust bands around the Sun as they may have appeared a few million years after formation. Thus, the debris system around HD98800B may have resulted from a failed terrestrial planet. We discuss briefly strategies for locating additional PDSs with SIRTF, which in turn will place constraints on how often terrestrial planets form.

We report these results as part of the NICMOS Instrument Definition Team's Environments of Nearby Stars program, which included observations of six TW Hya members. This work is supported by NASA grant NAG 5-3042. This paper is based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS5-26555.

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