Infrared Signatures of Disrupted Minor Planets at White Dwarfs
Abstract
Spitzer Space Observatory IRAC and MIPS photometric observations are presented for 20 white dwarfs with T eff lsim 20, 000 K and metal-contaminated photospheres. A warm circumstellar disk is detected at GD 16 and likely at PG 1457-086, while the remaining targets fail to reveal mid-infrared excess typical of dust disks, including a number of heavily polluted stars. Extending previous studies, over 50% of all single white dwarfs with implied metal-accretion rates dM/dtgsim 3 × 108 g s-1 display a warm infrared excess from orbiting dust; the likely result of a tidally destroyed minor planet. This benchmark accretion rate lies between the dust production rates of 106 g s-1 in the solar system zodiacal cloud and 1010 g s-1 often inferred for debris disks at main-sequence A-type stars. It is estimated that between 1% and 3% of all single white dwarfs with cooling ages less than around 0.5 Gyr possess circumstellar dust, signifying an underlying population of minor planets.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- April 2009
- DOI:
- 10.1088/0004-637X/694/2/805
- arXiv:
- arXiv:0901.0973
- Bibcode:
- 2009ApJ...694..805F
- Keywords:
-
- circumstellar matter;
- infrared: stars;
- minor planets;
- asteroids;
- planetary systems;
- stars: abundances;
- stars: evolution;
- stars: individual: GD 16 PG1457-086;
- stars: low-mass;
- brown dwarfs;
- white dwarfs;
- Astrophysics - Earth and Planetary Astrophysics;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 47 pages, accepted to ApJ