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Discovery of a peculiar DQ white dwarf

D. Carollo·S. T. Hodgkin·A. Spagna·R. L. Smart·M. G. Lattanzi·B. J. McLean·D. J. Pinfield
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Abstract

We report the discovery of a new carbon rich white dwarf that was identified during a proper motion survey for cool white dwarfs based on photographic material used for the construction of the Guide Star Catalog II. Its large proper motion (0.48 arcsec/yr) and faint apparent magnitude (V = 18.7) suggest a nearby object of low luminosity. A low-resolution spectrum taken with the William Herschel Telescope clearly shows strong C2 Deslandres-d'Azambuja and Swan bands, which identify the star as a DQ white dwarf. The strength of the Deslandres-d'Azambuja bands and the depression of the continuum in the Swan-band region are signs of enhanced carbon abundance for the given Teff. Comparison of our spectrophotometric data to published synthetic spectra suggests 6000 K < Teff < 8000 K although further analysis with specialized synthetic models appear necessary to derive both Teff and chemical composition. Finally, the range of spatial velocity estimated for this object makes it a likely member of the halo or thick disk population.

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D. Carollo, S. T. Hodgkin, A. Spagna, R. L. Smart, M. G. Lattanzi, B. J. McLean, D. J. Pinfield. 2002-08-27. Discovery of a peculiar DQ white dwarf. https://doi.org/10.1051/0004-6361%3A20021130

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