AAS Meeting #193 - Austin, Texas, January 1999
Session 69. Circumstellar Material
Display, Friday, January 8, 1999, 9:20am-6:30pm, Exhibit Hall 1

## [69.07] ISO and Sub-mm Imaging of Dusty Disks Around Vega-type Stars

S. B. Fajardo-Acosta, R. E. Stencel (U. of Denver), D. E. Backman (Franklin \& Marshall)

We present a comparison of far-infrared (60 \mum) and sub-millimeter (850 \mum) images of circumstellar dust of the Vega-type stars \alpha PsA (A3 V) and \epsilon Eri (K2 V). The 60 \mum images were obtained with the Infrared Space Observatory (ISO), using the PHOT C-100 array camera in its dedicated micromapping mode. The 60 \mum image of \alpha PsA was measured by Fajardo-Acosta et al.\ (1997, ApJ, 487, L151; 1998, ApJ, 503, L193); that of \epsilon Eri is reported for the first time here. The 850 \mum images were obtained with the sub-millimeter camera SCUBA at the James Clerk Maxwell Telescope (JCMT). The 850 \mum image of \alpha PsA was measured by Holland et al.\ (1998, Nature, 392, 788); that of \epsilon Eri was measured by Greaves et al.\ (1998, ApJ, 506, L133). The comparison of the far-infrared and sub-millimeter images aims at confirming the reality of the reported morphology of the dust regions around these sources. These observations were conducted with very different methods and instrumentation. However, both the ISO PHOT and JCMT SCUBA images of \alpha PsA show a nearly edge-on disk around it, oriented nearly north-south. Also, both observations of \epsilon Eri resolved extended dust around it. The SCUBA image shows a ring of dust around \epsilon Eri. The PHOT image of \epsilon Eri also shows similarly extended dust emission, but we also detected a central condensation of dust at the star position. We compared the spatial scales of the reported dust structures in these objects. We comment on plausible grain size distributions implied by these comparisons.