Mid-Infrared Imaging of Candidate Vega-like Systems

We have conducted deep mid-infrared imaging of a relatively nearby sample ofcandidate Vega-like stars using the OSCIR instrument on the CTIO 4-meter andKeck II 10-meter telescopes. Our discovery of a spatially-resolved disk aroundHR 4796A has already been reported (Jayawardhana et al. 1998). Here we presentimaging observations of the other members of the sample, including thediscovery that only the primary in the HD 35187 binary system appears to harbora substantial circumstellar disk and the possible detection of extended diskemission around 49 Ceti. We derive global properties of the dust disks, placeconstraints on their sizes, and discuss several interesting cases in detail.Although our targets are believed to be main sequence stars, we note thatseveral have large infrared excesses compared to prototype Vega-like systems,and may therefore be somewhat younger. The disk size constraints we derive, inmany cases, imply emission from relatively large ($\gtrsim$ 10$\mu$m) particlesat mid-infrared wavelengths.Comment: 15 pages and 2 PostScript figures, accepted for publication in The Astronomical Journa