SEARCH FOR VEGA-LIKE NEARBY STARS WITH 12 MICRON EXCESS

The identification of Vega-like main-sequence stars with 10-mu-m excess would permit important measurements of the spatial extent of the radiating material with ground-based telescopes. In fact, 55 of the 548 nearby A, F, G, and K dwarfs with IRAS catalog magnitudes at 12-mu-m appear to have excess 12-mu-m flux. However, for only two of these stars, beta Pic and zeta-Lep, was it possible, using small-aperture photometry at 2.2 and 10-mu-m, to verify that the 12-mu-m excess is with high likelihood associated with the star. For the remaining stars the apparent 12-mu-m excess was either traced to IRAS beam confusion or could not be verified at 10-mu-m. The typical 2.2-12-mu-m color of the 106 A, F, G, and K stars in the observing program is only 0.02 mag. Excess flux due to a Vega-like cloud which may surround some of the sources in our observing program, like alpha Lyrae, is thus typically not detectable at 10-mu-m.