The Nature of the 24 Micron Excess Emission from Hot White Dwarfs

Details The Nature of the 24 Micron Excess Emission from Hot White Dwarfs The Nature of the 24 Micron Excess Emission from Hot White Dwarfs

Mar 2008

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008sptz.prop50629c&link_type=abstract

Spitzer Proposal ID #50629

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Spitzer observations of the Helix Nebula have revealed a bright 24 and 70 um source at the central star, a white dwarf (WD) with an effective temperature of 110,000 K. A Spitzer IRS spectrum of this source confirms that the emission is dust continuum. The analysis of Spitzer observations leads to the conclusion that this hot WD is surrounded by a dust disk at a distance of 40-100 AU, and that the dust may be freshly produced by collisions of dynamically perturbed Kuiper-Belt-like Objects or comets. To determine whether the dust disk around the Helix central WD is a common phenomenon, we have conducted a MIPS 24 um survey for a sample of 72 hot (>100,000 K) WDs that either are in old planetary nebulae or belong to a variety of spectral classes. Among the 51 objects that have been observed, four hot WDs are detected at 24 um and show fluxes more than 100 times higher than their expected photospheric emission. To determine the nature and origin of the excess 24 um emission we request (1) low-resolution IRS observations to unambiguously separate line and continuum emission components and to search for mineralogical features of dust grains; (2) IRAC observations at 3.6-8.0 um; and (3) MIPS 70 um observations of these hot WDs. These observations will allow us to measure the dust continuum emission, derive its temperature and distance from the central star, and assess the origin of the dust.

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