A Dusty Component to the Gaseous Debris Disk around the White Dwarf SDSS J1228+1040

TL;DR

This study provides the first evidence of both dust and gas coexisting in a debris disk around a white dwarf, using infrared observations to model the disk's properties and temperature.

Contribution

It demonstrates the simultaneous presence of dust and gas in a white dwarf's debris disk, expanding understanding of circumstellar environments around such stars.

Findings

Infrared excess indicates dust presence alongside gaseous disk.

Disk modeled as optically thick, geometrically thin with high inner temperatures (~1700 K).

First evidence of dust and gas coexisting around a moderately hot white dwarf.

Abstract

We present ISAAC spectroscopy and ISAAC, UKIDSS and Spitzer Space Telescope broad-band photometry of SDSS J1228+1040 -- a white dwarf for which evidence of a gaseous metal-rich circumstellar disk has previously been found from optical emission lines. The data show a clear excess in the near- and mid-infrared, providing compelling evidence for the presence of dust in addition to the previously identified gaseous debris disk around the star. The infrared excess can be modelled in terms of an optically thick but geometrically thin disk. We find that the inner disk temperatures must be relatively high (~1700 K) in order to fit the SED in the near-infrared. These data provide the first evidence for the co-existence of both gas and dust in a disk around a white dwarf, and show that their presence is possible even around moderately hot (~22,000 K) stars.