Frequency of Debris Disks around Solar‐Type Stars: First Results from aSpitzerMIPS Survey

We have searched for infrared excesses around a well defined sample of 69 FGKmain-sequence field stars. These stars were selected without regard to theirage, metallicity, or any previous detection of IR excess; they have a medianage of ~4 Gyr. We have detected 70 um excesses around 7 stars at the 3-sigmaconfidence level. This extra emission is produced by cool material (< 100 K)located beyond 10 AU, well outside the ``habitable zones'' of these systems andconsistent with the presence of Kuiper Belt analogs with ~100 times moreemitting surface area than in our own planetary system. Only one star, HD69830, shows excess emission at 24 um, corresponding to dust with temperatures> 300 K located inside of 1 AU. While debris disks with Ld/L* > 10^-3 are rarearound old FGK stars, we find that the disk frequency increases from 2+-2% forLd/L* > 10^-4 to 12+-5% for Ld/L* > 10^-5. This trend in the disk luminositydistribution is consistent with the estimated dust in our solar system beingwithin an order of magnitude, greater or less, than the typical level aroundsimilar nearby stars.Comment: 11 figure