The Evolution of Warm Debris Disks: Implications for Recent Collisions


First Author:
Peter Abraham
Email: abraham AT konkoly.hu
Konkoly Observatory of the Hungarian Academy of Sciences
Konkoly Thege M. ut 15-17
Budapest, H-1121, Hungary
Coauthors:
Moor, Attila, Konkoly Observatory of the Hungarian Academy of Sciences
Pascucci, Ilaria, Johns Hopkins University
Apai, Daniel, Space Telescope Science Institute
Kiss, Csaba, Konkoly Observatory of the Hungarian Academy of Sciences
Grady, Carol, NASA Goddard Space Flight Center & Eureka Scientific
Henning, Thomas, Max-Planck-Institut für Astronomie
Juhasz, Attila, Max-Planck-Institut für Astronomie

Abstract
We report on the results of a Spitzer program devoted to studying debris disks around F-type stars. The motivation of the program was to outline disk evolution effects in a constrained stellar mass range, and also to make the bridge between the major Spitzer surveys of debris disks around A-type and G,K-type stars. We observed 78 F-type stars with IRS and MIPS, all of them with previous indications for infrared excess from IRAS or ISO. The observed debris disk population shows a large variety in dust temperatures. In this contribution we report the discovery of four warm debris disks, which significantly increases the number of such systems known. Based on the fractional luminosity and age, three out of the four warm debris systems are consistent with a steady state disk evolution picture. The infrared luminosity of the fourth system is too high to be explained by a steady state evolution, but it is consistent with a recent collisional cascade. This picture is reinforced by the prominent silicate emission features present in the IRS spectrum. The observed diversity of warm debris disks is consistent with a simple evolutionary picture: collisional cascades inject large amounts of small grains into the disk; with time, smaller grains are removed faster by radiation pressure resulting in the decay of the infrared excess and the weakening of the silicate features. Transient warm disks may be the closest analogues yet to the Late Heavy Bombardment in our Solar System. Such systems could be primary targets for follow-up observations searching for planets.
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