The Distribution of Debris Disks around Solar-Type Stars
Authors:
          Geoffrey Bryden, JPL
          Chas Beichman, MSC
          David Trilling, Arizona
          George Rieke, Arizona
          Karl Stapelfeldt, JPL
          Mike Werner, JPL

Abstract:
          Using the MIPS camera on the Spitzer Space Telescope, we have searched for infrared excesses around 58 FGK main-sequence field stars.  With a median age of ~5 Gyr, the stars are older than those which typically have excess emission due to a debris disk. Nevertheless, we have detected 70 micron excesses around 6 stars at the 3-sigma confidence level.  This extra emission is produced by cool material (<100 K) located beyond 10 AU, well outside the ''habitable zones'' of these systems and consistent with the presence of Kuiper Belt analogues with ~100 times more emitting surface area than in our own planetary system.  Only one star, HD69830, shows excess emission at 24 microns, corresponding to dust with temperatures > 300 K located inside of 1 AU.  While debris disks with L_disk/L_* > 10^-3 are rare around old FGK stars, we find that the disk frequency increases from 2+-2% for disks with L_disk/L_* > 10^-4 to 11+-5% for L_d/L_* > 10^-5.  Fits of this distribution suggest that the amount of dust in our Solar System is not largely below the average for similar field stars.