Infrared Signatures of Disrupted Minor Planets at White Dwarfs

TL;DR

This study uses infrared observations to detect dust disks around white dwarfs, revealing that a significant fraction of these stars with metal pollution have circumstellar dust likely from tidally disrupted minor planets.

Contribution

It extends previous research by establishing a correlation between metal accretion rates and the presence of warm dust disks around white dwarfs, indicating ongoing planetary system disruption.

Findings

Over 50% of metal-polluted white dwarfs with high accretion rates have dust disks.

Approximately 1-3% of young white dwarfs host circumstellar dust.

Detected disks suggest minor planets are commonly disrupted around white dwarfs.

Abstract

Spitzer Space Observatory IRAC and MIPS photometric observations are presented for 20 white dwarfs with T < 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/dt > 3e8 g/s 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 1e6 g/s in the solar system zodiacal cloud and 1e10 g/s 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.