A new model atmosphere analysis for the peculiar DQ white dwarf discovered by Carollo et al. (2002) is presented. The effective temperature and carbon abundance have been estimated by fitting both the photometric data (UBJVRFINJHK) and a low resolution spectrum (3500 < λ < 7500 Å) with a new model grid for helium-rich white dwarfs with traces of carbon (DQ stars). We estimate Teff ≃ 5120 ± 200 K and log[C/He] ≃ -5.8 ± 0.5, which make GSC2U J131147.2+292348 the coolest DQ star ever observed. This result indicates that the hypothetical transition from C2 to C2H molecules around Teff = 6000 K, which was inferred to explain the absence of DQ stars at lower temperatures, needs to be reconsidered.
|Journal||Astronomy and Astrophysics|
|Publication status||Published - Mar 2003|
Bibliographical noteCopyright ESO 2003. First published in Astronomy and Astrophysics, Vol. 400, No. 1, published by EDP Sciences. The original publication is available at http://dx.doi.org/10.1051/0004-6361:20030132
- Stars: Individual: GSC2U J131147.2+292348
- Stars: Kinematics
- Techniques: Spectroscopic
- White dwarfs