A Systematic Search for Gaseous Debris Disks in DESI Early Data Release White Dwarfs

TL;DR

This study conducts a systematic search for gaseous debris disks around white dwarfs using DESI data, identifying candidate systems with emission features and infrared excess, highlighting the potential and challenges of large spectroscopic surveys.

Contribution

Introduces a new method for detecting gaseous debris disks in white dwarfs using DESI spectra, revealing a higher candidate rate and emphasizing the need for follow-up confirmation.

Findings

22 candidate systems with emission features identified

Candidate rate of 0.81%, higher than previous estimates

Some candidates show infrared excess indicating dust presence

Abstract

Detecting gaseous debris disks around white dwarfs offers a unique window into the ultimate fate of planetary systems and the composition of accreted planetary material. Here we present a systematic search for such disks through the Ca II infrared triplet using the Dark Energy Spectroscopic Instrument (DESI) Early Data Release. From a parent sample of 2706 spectroscopically confirmed white dwarfs, we identify 22 candidate systems showing tentative emission-line features, which corresponds to a raw occurrence rate of 0.81%, more than ten times higher than previous estimates. The detected emission lines are predominantly weak and require confirmation by follow-up observations. Three of these candidates also exhibit infrared excess in WISE photometry, suggesting a possible coexistence of gas and dust. However, the high candidate rate indicates that most are likely false positives due to telluric residuals or unresolved binaries. This work demonstrates the potential of DESI spectra for blind searches of rare circumstellar phenomena. The recently released DESI DR1, with its substantially larger spectroscopic sample, will enable searches for more gaseous disks and provide better insights into their occurrence and nature.