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D. W. Koerner (U. Pennsylvania), G. Schneider (U. Arizona), B. A. Smith (IfA), E. E. Becklin (UCLA), D. C. Hines (UA), J. D. Kirkpatrick (IPAC), P.J. Lowrance (UCLA), R. Meier (IfA), M. Reike (UA), R. J. Terrile (JPL), R. I. Thompson (UA), NICMOS/IDT EONS Team
We have carried out a coronagraphic imaging study of circumstellar disk candidates as part of NICMOS IDT investigations of the environments of nearby stars. Here we present images of circumstellar nebulosity around the classical T Tauri star, GM Aurigae, at \lambda = 1.1 and 1.6 \mum. The emission extends beyond 2.8'' (450 AU) from the star with brightness falling off radially as R-2.5. The flux ratio between the two wavelengths differs little from that expected for a K5 star like GM Aur, suggesting that scattering grains include a substantial population with sizes larger than 1 \mum. Preliminary modeling of the emission confirms its origin in stellar light reflected off the surface of a flared circumstellar disk and indicates an inclination 60\circ from face on. These results agree well with the appearance of CO(2arrow1) emission in aperture synthesis images from the Owens Valley Millimeter Array, and with the morphology of optical nebulosity in psf-subtracted exposures taken by the WFPC2 science team. Further, the high-resolution constraint on size and orientation enables a definitive interpretation of the velocity structure from kinematic modeling of CO(2arrow1) images at lower resolution: it is demonstrated unequivocally that the gas is centrifugally supported and in Keplerian rotation within the confines of a disk centered on the star. This work is supported by NASA grant NAG 5-3042, and 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.
The author(s) of this abstract have provided an email address for comments about the abstract: davidk@uraniborg.physics.upenn.edu