The Dust cloud around the White Dwarf G 29 - 38

We present new observations of the white dwarf G 29-38 with the camera (4.5 and 8 μm), photometer (24 μm), and spectrograph (5.5–14 μm) of the Spitzer Space Telescope. This star has an exceptionally large infrared excess amounting to 3% of the bolometric luminosity. The spectral energy distribution has a continuum peak around 4.5 μm and a 9–11 μm emission feature 1.25 times brighter than the continuum. A mixture of amorphous olivine and a small amount of forsterite in an emitting region 1–5 R⊙ from the star can reproduce the shape of the 9–11 μm feature. The spectral energy distribution also appears to require amorphous carbon to explain the hot continuum. Our new measurements support the idea that a relatively recent disruption of a comet or asteroid created the cloud. Subject headings: white dwarfs, stars: individual (G29-38, WD 2326+049), infrared: stars