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A. Evans (Keele University)
The He on a hot white dwarf may explosively reignite, causing the star become a Born-Again Giant (BAG). Such 'Helium Flashes' play an important part in the production and ejection of material into the interstellar medium, because as many as 25% of low-mass stars may undergo such an event.
We review the results of ground-based infrared, sub-millimeter and Spitzer data on BAG stars, including the rapidly varying Sakurai's Object (V4334 SGr) and one of the earliest known BAGs, CK Vul. In many cases we just see (almost) featureless emission by carbonaceous dust that is optically thick shortward of 1\,\mum. Fitting the infrared-submillimeter spectral energy distribution points in some cases to the presence of very large grains and relatively flat grain size distribution, suggesting that growth and/or coagulation may occur in the circumstellar environment.
This work is supported by JPL.
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Bulletin of the American Astronomical Society, 37 #2
© 2005. The American Astronomical Soceity.