Strengthening the Case for Asteroidal Accrection: Evidence for Subtle and Diverse Disks at White Dwarfs

TL;DR

This study presents infrared observations of ten white dwarfs, revealing diverse and subtle circumstellar dust disks that support the idea of ongoing accretion of disrupted minor planets, even in cases with minimal infrared excess.

Contribution

It provides new infrared photometry evidence for diverse, subtle disks around white dwarfs, strengthening the link between heavy element pollution and planetary debris accretion.

Findings

Infrared excess detected at HE 2221-1630 indicating a substantial disk.

Modest excesses at HE 0106-3253 and HE 0307+0746 suggest narrow dust rings.

Possible large inner hole in dust rings at PG 1225-079 and G166-58.

Abstract

Spitzer Space Telescope IRAC 3-8 micron and AKARI IRC 2-4 micron photometry are reported for ten white dwarfs with photospheric heavy elements; nine relatively cool stars with photospheric calcium, and one hotter star with a peculiar high carbon abundance. A substantial infrared excess is detected at HE 2221-1630, while modest excess emissions are identified at HE 0106-3253 and HE 0307+0746, implying these latter two stars have relatively narrow (Delta r < 0.1 Rsol) rings of circumstellar dust. A likely 7.9 micron excess is found at PG 1225-079 and may represent, together with G166-58, a sub-class of dust ring with a large inner hole. The existence of attenuated disks at white dwarfs substantiates the connection between their photospheric heavy elements and the accretion of disrupted minor planets, indicating many polluted white dwarfs may harbor orbiting dust, even those lacking an obvious infrared excess.