Nearby Debris Disk Systems with High Fractional Luminosity Reconsidered

By searching the IRAS and ISO databases we compiled a list of 60 debris diskswhich exhibit the highest fractional luminosity values (fd>10^-4) in thevicinity of the Sun (d<120pc). Eleven out of these 60 systems are newdiscoveries. Special care was taken to exclude bogus disks from the sample. Wecomputed the fractional luminosity values using available IRAS, ISO, andSpitzer data, and analysed the galactic space velocities of the objects. Theresults revealed that stars with disks of high fractional luminosity oftenbelong to young stellar kinematic groups, providing an opportunity to obtainimproved age estimates for these systems. We found that practically all diskswith fd>5x10^-4 are younger than 100Myr. The distribution of the disks in thefractional luminosity versus age diagram indicates that (1) the number of oldsystems with high fd is lower than was claimed before; (2) there exist manyrelatively young disks of moderate fractional luminosity; and (3) comparing theobservations with a current theoretical model of debris disk evolution ageneral good agreement could be found.Comment: 47 pages, 6 figures, AASTeX preprint (accepted for publication in the Astrophysical Journal); refined the text parts of table 6 and