Abstract

Completing the census of infrared bright disks at nearby polluted white dwarfs

Carolina Bergfors (University College London)

Jay Farihi (UCL), Patrick Dufour (Université de Montréal), Marco Rocchetto (UCL)

We present Spitzer IRAC observations of 15 metal polluted white dwarfs, in search of dust discs created by tidal disruption of minor planets. Two stars in our target sample, and possibly three, show subtle infrared excess emission consistent with the presence of narrow circumstellar dust rings. The weak infrared excess around one of these makes it the the coolest known white dwarf with an excess at 3.6 micron, and the first DZ star with a bright disc. 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 1 Myr, 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.

Mode of presentation: poster