AAS 201st Meeting, January, 2003
Session 20. Star Formation I
Poster, Monday, January 6, 2003, 9:20am-6:30pm, Exhibit Hall AB

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[20.20] HST/STIS Coronagraphic Imaging of the Disk of DM Tauri

C. Grady (Eureka Scientific, NOAO, and GSFC), B. Woodgate (NASA's GSFC), K. Stapelfeldt (JPL), D. Padgett (SIRTF Science Center), B. Stecklum (Thuringer Landessternwarte Tautenburg, Germany), T. Henning (MPIA, Heidelberg, Germany), V. Grinin (Crimean Astrophysical Observatory), A. Quirrenbach (UCSD), M. Clampin (STScI)

Near-IR studies of pre-Main Sequence stars have suggested that by 5 Myr signatures of near-stellar dust become rare, presumably due to clearing of the inner disk, while in some systems by 8 Myr the transition to a debris disk + planetary system may be complete. As part of a study of the evolution of protoplanetary disks, we present broadband optical coronagraphic imagery of the 5 Myr old T Tauri star, DM Tau obtained with HST/STIS. At V>14.3, DM Tau is the faintest object coronagraphically imaged with HST. We detect an asymmetric ring of bright, presumably reflection, nebulosity surrounding the star, with an inner dark oval with radius along its major axis= 2.2" (308 AU). The orientation and inclination for the oval, determined from its minor/major axis ratio, is consistent with the disk major axis and inclination determined from the millimeter. Beyond the dark oval, a bright ring of nebulosity is asymmetrically distributed about the star extending 3.95" (550 AU) along the major axis. We identify the brighter portion of the ring to the NE of the star along the system minor axis as the forward scattering side of the disk.This bright ring drops in surface brightness as r(-2), indicating that we detect material which is flared with respect to the disk midplane. In tandem with the millimeter continuum data for DM Tau (Simon et al. 2000), we interpret the dark oval as indicating the presence of a region which is either geometrically flatter than the outer disk or which is largely devoid of submicron grains.

This study was supported by HST-GO-9136.

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