Dr. Ted von Hippel
U. Texas
University of Florida Astronomy Colloquium - Jan. 30th, 2008
Debris Disk White Dwarfs and the Fate of Planetary Systems
I will present Spitzer and ground-based observations of a hand full of metal-polluted white dwarfs with circumstellar debris disks. Most of these objects are newly discovered. For one of the white dwarfs, I will present Spitzer 5.5-14 micron spectroscopy, highlighting the 9-11 micron emission feature caused by mixture of amorphous olivine and forsterite. The emitting region is located 0.1-5 Rsun from the WDs. Our measurements support the idea that disruptions of asteroids created the debris disks. Based on the properties of these stars, I interpret the bulk of the metal-polluted white dwarfs as resulting from planetary system bodies being ground down during the late stages of stellar evolution.