Spitzer Surveys of IR Excesses of White Dwarfs

TL;DR

This paper reviews Spitzer Space Telescope surveys detecting infrared excesses around white dwarfs, revealing two types of circumstellar dust disks linked to different WD temperatures and origins.

Contribution

It provides a comprehensive overview of Spitzer IR surveys identifying and characterizing dust disks around white dwarfs, highlighting their different properties and origins.

Findings

Small disks around cool WDs within the Roche limit from tidally disrupted asteroids.

Large disks around hot WDs at tens of AU possibly from Kuiper Belt-like collisions.

Multiple Spitzer surveys have systematically detected IR excesses indicating circumstellar dust.

Abstract

IR excesses of white dwarfs (WDs) can be used to diagnose the presence of low-mass companions, planets, and circumstellar dust. Using different combinations of wavelengths and WD temperatures, circumstellar dust at different radial distances can be surveyed. The Spitzer Space Telescope has been used to search for IR excesses of white dwarfs. Two types of circumstellar dust disks have been found: (1) small disks around cool WDs with Teff < 20,000 K, and (2) large disks around hot WDs with Teff > 100,000 K. The small dust disks are within the Roche limit, and are commonly accepted to have originated from tidally crushed asteroids. The large dust disks, at tens of AU from the central WDs, have been suggested to be produced by increased collisions among Kuiper Belt-like objects. In this paper, we discuss Spitzer IRAC surveys of small dust disks around cool WDs, a MIPS survey of large dust disks around hot WDs, and an archival Spitzer survey of IR excesses of WDs.