Astronomy and Astrophysics – Astrophysics – Solar and Stellar Astrophysics
Scientific paper
2009-02-20
Astrophys.J.696:1461-1465,2009
Astronomy and Astrophysics
Astrophysics
Solar and Stellar Astrophysics
14 pages, 3 figures, accepted for publication in ApJ
Scientific paper
10.1088/0004-637X/696/2/1461
A spectroscopic analysis of the DBA (or DAB) white dwarf KUV 02196+2816 is presented. The observed hydrogen and helium line profiles are shown to be incompatible with model spectra calculated under the assumption of a homogeneous hydrogen and helium chemical composition. In contrast, an excellent fit to the optical spectrum of KUV 02196+2816 can be achieved if the object is interpreted as an unresolved double degenerate composed of a hydrogen-line DA star and a helium-line DB star. The atmospheric parameters obtained from the best fit are Teff=27,170 K and log g=8.09 for the DA star, Teff=36,340 K and log g=8.09 for the DB star, which implies that the total mass of the system (M~1.4 Msol) is very close to the Chandrasekhar limit. Moreover, the effective temperature of the DB stars lies well within the so-called DB gap where very few bright DB stars are found. The implications of this discovery with respect to the DAB and DBA spectral classes and to the evolution of double degenerate binaries are discussed.
Bergeron Pierre
Dufour Pierre
Limoges Marie-Michele
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