A 25 micron search for Vega-like disks around main-sequence stars with ISO

We present an ISO 25 mum photometric survey of a sample of 81 nearby main-sequence stars in order to determine the incidence of warm dust disks. All stars were detected by ISO. We used an empirical relation to estimate the photospheric flux of the stars at 25 mum. We find 5 stars (6%) with excess above the photospheric flux which we attribute to a Vega-like disk. These stars show disk temperatures not warmer than 120 K. Our study indicates that warm disks are relatively rare. Not a single star in our sample older than 400 Myr has a warm disk. We find an upper limit of M-disk = 2 x 10(5) M+ for the mass of the disks which we did not detect.