Near-Infrared Imaging of White Dwarfs with Candidate Debris Disks

TL;DR

This study used near-infrared imaging to investigate white dwarf candidates for debris disks, finding some infrared excesses but with uncertainties about their origins, highlighting the need for further observations.

Contribution

First near-infrared imaging survey of WIRED SDSS DR7 white dwarf debris disk candidates, assessing the nature of infrared excesses and identifying potential false positives.

Findings

Seven white dwarfs show infrared excess mostly at WISE bands.

Four excesses are due to background galaxies or low-mass dwarfs.

One excess suggests an unresolved L0 companion.

Abstract

We have carried out $JHK_s$ imaging of 12 white dwarf debris disk candidates from the WIRED SDSS DR7 catalog, aiming to confirm or rule out disks among these sources. On the basis of positional identification and the flux density spectra, we find that seven white dwarfs have excess infrared emission, but mostly at WISE W1 and W2 bands, four are due to nearby red objects consistent with background galaxies or very low mass dwarfs, and one exhibits excess emission at $JHK_s$ consistent with an unresolved L0 companion at the correct distance. While our photometry is not inconsistent with all seven excesses arising from disks, the stellar properties are distinct from the known population of debris disk white dwarfs, making the possibility questionable. In order to further investigate the nature of these infrared sources, warm Spitzer imaging is needed, which may help resolve galaxies from the white dwarfs and provide more accurate flux measurements.