Abstract

Dust disks created by tidal disruption of minor planets have been observed around metal polluted white dwarfs using a variety of techniques, providing important clues to the fate of terrestrial planetary systems at 2-3 Msol stars. We present results from Spitzer IRAC observations of 15 white dwarfs; a few of which are highly polluted, but most of which show modest metal abundances. We find two, and possibly three, new stars with disks, all of which show rather subtle infrared excesses. One of these is the coolest star known to exhibit an excess at 3 microns, and the first DZ type star with a bright disk. All together our data corroborate a picture where 1) disks at metal-enriched white dwarfs are commonplace and most escape detection in the infrared, 2) the disks are long lived, having lifetimes on the order of 1e6 yr, and 3) the frequency of bright, IR detectable disks decreases with age, on a timescale of roughly 500 Myr, suggesting large planetesimal disruptions decline on this same timescale.

Presentation

Poster