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Paper: FUSE Observation of Silicon in the Photosphere of the DBA White Dwarf GD 61
Volume: 348, Astrophysics in the Far Ultraviolet: Five Years of Discovery with FUSE
Page: 239
Authors: Wesemael, F.; Petitclerc, N.; Chayer, P.; Kruk, J.W.; Pesant, S.; Tardif, B.
Abstract: FUSE observations of the cool (Teff ∼ 17; 000 K) DBA white dwarf reveal that the carbon features observed in several hotter DB stars are absent, but that photospheric transitions associated with the Si III ion are present. This may be the first indication that the mechanism which allows carbon to remain conspicuous in hotter objects, postulated to be a stellar wind, may well have turned off by the time a DB star cools down to 17,000 K. The photospheres of cooler DB stars are likely to be dominated instead by accretion from the ISM and, at even cooler temperatures, by convective dredge-up of carbon.
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