Letter to the Editor
INAF, Osservatorio Astronomico di Torino, 10025 Pino Torinese, Italy
2 Cambridge Astronomical Survey Unit, Institute of Astronomy, Madingley Road, Cambridge, CB3 0HA, UK
3 Space Telescope Science Institute (STScI), Baltimore, MD 21218, USA
4 Astrophysics Research Institute, Liverpool John Moores University, Birkenhead, CH41 1LD, UK
Corresponding author: D. Carollo, firstname.lastname@example.org
Accepted: 2 August 2002
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 ( arcsec/yr) and faint apparent magnitude () 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 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.
Key words: white dwarfs / stars: carbon / stars: kinematics / stars: individual: GSC2U J131147.2+292348 / astrometry / techniques: spectroscopic
Based on observations made with the William Herschel Telescope operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias.
© ESO, 2002