Farihi, J; Zuckerman, B; Becklin, EE; (2008) Spitzer IRAC observations of white dwarfs. I. Warm dust at metal-rich degenerates. Astrophysical Journal , 674 (1) pp. 431-446. 10.1086/521715.

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Abstract

This paper presents the results of a Spitzer IRAC 3-8 μm photometric search for warm dust orbiting 17 nearby, metal-rich white dwarfs, 15 of which apparently have hydrogen-dominated atmospheres (type DAZ). G166-58, G29-38, and GD 362 manifest excess emission in their IRAC fluxes and the latter two are known to harbor dust grains warm enough to radiate detectable emission at near-infrared wavelengths as short as 2 μm. Their IRAC fluxes display differences compatible with a relatively larger amount of cooler dust at GD 362. G166-58 is presently unique in that it appears to exhibit excess flux only at wavelengths longer than about 5 μm. Evidence is presented that this mid-infrared emission is most likely associated with the white dwarf, indicating that G166-58 bears circumstellar dust no warmer than T ∼ 400 K. The remaining 14 targets reveal no reliable mid-infrared excess, indicating the majority of DAZ stars do not have warm debris disks sufficiently opaque to be detected by IRAC.

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