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Paper: An Extremely Carbon-Rich White Dwarf in the Direction of the Virgo-Coma Cluster
Volume: 372, 15th European Workshop on White Dwarfs
Page: 273
Authors: de Martino, D.; Koester, D.; Treves, A.; Sbarufatti, B.; Falomo, R.
Abstract: The blue object 1222+102 lies in the direction of the Virgo-Coma cluster and well inside the boundaries of the galaxy NGC4380. While it was formerly proposed as a result of expulsion from the galactic nucleus, from a recent ESO�VLT spectroscopic survey of BL LAC objects, Sbarufatti et al. (2006) suggest a stellar nature, implying a galactic origin. Here we present a further investigation of the FORS1 spectrum which indicates that 1222+102 is a DQ white dwarf with one of the highest carbon abundance known so far. This object can hence be definitively ascribed as a high latitude galactic white dwarf at a distance of about 110-120pc. Its high temperature and carbon abundance suggest that it might be a member of the recently proposed (Dufour et al. 2005; Koester & Knist 2006) separate population of carbon-rich DQ stars with an abundance 1 dex higher at the same effective temperature of the primary sequence.
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