The polluted atmosphere of the white dwarf NLTT 25792 and the diversity of circumstellar environments
- Astronomický ústav, Akademie věd České republiky, Fričova 298, CZ-251 65 Ondřejov (Czech Republic)
We present an analysis of X-shooter spectra of the polluted, hydrogen-rich white dwarf NLTT 25792. The spectra show strong lines of calcium (Ca H and K, near-infrared calcium triplet, and Ca Iλ4226) and numerous lines of iron along with magnesium and aluminum lines from which we draw the abundance pattern. Moreover, the photospheric Ca H and K lines are possibly blended with a circumstellar component shifted by –20 km s{sup –1} relative to the photosphere. A comparison with a sample of four white dwarfs with similar parameters show considerable variations in their abundance patterns, particularly in the calcium to magnesium abundance ratio that varies by a factor of five within this sample. The observed variations, even after accounting for diffusion effects, imply similar variations in the putative accretion source. Also, we find that silicon and sodium are significantly underabundant in the atmosphere of NLTT 25792, a fact that may offer some clues on the nature of the accretion source.
- OSTI ID:
- 22348490
- Journal Information:
- Astrophysical Journal, Vol. 779, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
Similar Records
A White Dwarf with Transiting Circumstellar Material Far outside the Roche Limit
STRENGTHENING THE CASE FOR ASTEROIDAL ACCRETION: EVIDENCE FOR SUBTLE AND DIVERSE DISKS AT WHITE DWARFS