Infrared Space Observatory photometric search of main-sequence stars for Vega-type systems

We obtained 3.6-20 mu m photometry of 38 bright [IRAS F-nu(12 mu m) > 0.7 J y] main-sequence stars with the Infrared Space Observatory (ISO). Observati ons were conducted with the ISOPHOT instrument, in the single-pointing phot ometry mode, through filters at 3.6, 11.5, and 20.0 mu m. We searched for e xcess (Vega-type) emission from dust at temperatures greater than or simila r to 100 K, located at similar to 1-60 AU from the stars. We thus sampled d ust at warm, terrestrial material temperatures and at cool (similar to 100 K) temperatures of possible Kuiper Belt-type regions in these systems. We d etected 20 mu m excesses from similar to 14% of our sources, but we did not detect 11.5 mu m excesses from any of them. We present single-temperature blackbody models of the location and density of dust emission around 10 sta rs, two of them (29 Cyg and Gl 816) with excesses newly reported here. We m ake a thorough comparison of ISO and IRAS data on our target stars and prop ose a new calibration procedure for ISOPHOT staring measurements at 3.6, 11 .5, and 20 mu m.