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C.A. Grady (NOAO/STIS), B. Woodgate, T. Gull, R. Kimble, C. Bowers, S. Heap, S. Maran (NASA's GSFC), A. Boggess (CUA), A. Danks (Raytheon PSC), D. Lindler (ACC, Inc.), J. Linsky (JILA, U. Colorado), W. Moos (JHU), F. Roesler (U. Wisconsin), J.G. Timothy (Nightsen, Inc.)
We present the results of a coronagraphic imaging survey of some of the nearest and optically brightest Herbig Ae/Be (HAEBE) stars made with the Hubble Space Telescope and the Space Telescope Imaging Spectrograph. Our sample includes 9 nearby HAEBE stars with ages spanning 0.6 to more than 10 Myr. One of our sample members was previously known to have a nearby companion: we report the detection of stars offset 1.8 - 2.0" from their primaries in two additional cases : HD 36112 and CQ Tau. Our sample contains two stars, AB Aur and HD 100546, with envelopes extending more than 1000 AU from the stars. Both envelopes show band structure in their outer regions, which is closest to the star in the direction of the star's proper motion. One other system, CQ Tau, shows nebulosity at comparable distances, but with insufficient S/N to probe the detailed morphology. The morphology of the nebulosity around CQ Tau is broadly similar to SU Aur. The STIS data indicate survival of envelopes through much, if not all, of the star's pre-main sequence lifetime, but with surface brightness decreasing with stellar age. Disks are detected in two cases (HD 163296 and HD 100546). When compared with \beta Pic, the STIS data provide evidence for increasing flattening of the disk material with increasing stellar age. The disks of a number of millimeter-bright Herbig Ae/Be stars are not detected by STIS: these are stars with IR spectral energy distributions indicating the presence of larger grains. The implications for optical and near-IR imaging of protoplanetary disks will be discussed.
The author(s) of this abstract have provided an email address for comments about the abstract: cgrady@echelle.gsfc.nasa.gov