Near-ultraviolet and optical effects of Debris Disks around White Dwarfs

TL;DR

This paper explores how debris disks around white dwarfs can be detected through their effects on near-UV and optical wavelengths, providing a new method to infer disk properties.

Contribution

It demonstrates the theoretical feasibility of detecting debris disks via near-UV and optical effects in the star+disk spectrum, offering a novel observational approach.

Findings

Near-UV and optical effects can reveal disk properties such as mass and composition.

Detection depends on the disk's optical depth and inclination.

Effects differ between debris disks and dust shells, aiding in distinguishing them.

Abstract

Studies of debris disks around white dwarfs (WDs) have focused on infrared wavelengths because debris disks are much colder than the star and are believed to contribute to the spectrum only at longer wavelengths. Nevertheless, these disks are made of dust grains which absorb and scatter near-UV and optical photons from the WD, leaving a fingerprint that can be used to further constrain disk properties. Our goal is to show that it is possible to detect near-UV and optical effects of debris disks in the star + disk integrated spectrum. We make theoretical calculations and discuss the necessary observational conditions to detect the near-UV and optical effects. We show how these effects can be used to infer the disk mass, composition, optical depth, and inclination relative to the line of sight. If the IR excess is due to a disk, then near-UV and optical effects should be observed in only some systems, not all of them, while for dust shells the effects should be observed in all systems.