AAS Meeting #193 - Austin, Texas, January 1999
Session 89. Protoplanetary Disks, Molecular Clouds
Oral, Friday, January 8, 1999, 2:00-3:30pm, Room 6 (A and B)

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[89.05] NIR Imaging of the HR4796A Circumstellar Disk

B.A. Smith (Univ. of Hawaii), G. Schneider (Univ. of Az.), E.E. Becklin (UCLA), D.W. Koerner (Univ. of Penn.), R. Meier (Univ. of Hawaii), R.J. Terrile (JPL), D. C. Hines (Univ. of Az.), P.J. Lowrance (UCLA), R.I. Thompson (Univ. of Az.)

We report the first near infrared imaging of a circumstellar annular disk around the young (\approx 10Myr) star HR4796A. Observations obtained on 15 March and 16 August, 1998, using the HST/NICMOS coronagraph, reveal a ring-like symmetrical structure seen at 1.1 and 1.6 microns peaking in reflected intensity \approx70AU (1.1") from the central A0V star. The annulus, with a characteristic width of \approx15AU (0.2"), is abruptly truncated at both the inner and outer edges. The interior region of the disk-plane appears to be optically thin, and may be relatively free of scattering material. These observations, which place the major axis of the ring at a PA of \approx28 degrees, inclined \approx75 degrees, are in good agreement with the nearly contemporaneous (16 March) thermal infrared detection of an inner truncated disk seen in emission as reported by Koerner, et. al (1998, ApJ, 503, L83) and Jayawardhana, et. al. (1998, ApJ, 503, L79). The confinement of material to this relatively narrow zone implies dynamical constraints on the disk particles by one or more yet unseen orbiting bodies.

We report these results as part of the NICMOS IDT Environments of Nearby Stars program. 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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