"The Polluted Atmosphere of the White Dwarf NLTT 25792 and the Diversity of Circumstellar Environments"@en . . . "1" . "The Polluted Atmosphere of the White Dwarf NLTT 25792 and the Diversity of Circumstellar Environments"@en . "stars; abundances; atmospheres"@en . "RIV/67985815:_____/13:00399742!RIV14-GA0-67985815" . "I, P(GA13-14581S), P(GAP209/12/0217)" . . . . . "Vennes, Stephane" . . "779" . . "Vennes, Stephane" . "000328160100070" . "US - Spojen\u00E9 st\u00E1ty americk\u00E9" . . . . "97005" . . . "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&K, near-infrared calcium triplet, and Ca I\u03BB4226) and numerous lines of iron along with magnesium and aluminum lines from which we draw the abundance pattern. Moreover, the photospheric Ca H&K lines are possibly blended with a circumstellar component shifted by \u201320 km s\u20131 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." . . "2"^^ . "2"^^ . "10.1088/0004-637X/779/1/70" . . "Kawka, Adela" . "RIV/67985815:_____/13:00399742" . "The Polluted Atmosphere of the White Dwarf NLTT 25792 and the Diversity of Circumstellar Environments" . "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&K, near-infrared calcium triplet, and Ca I\u03BB4226) and numerous lines of iron along with magnesium and aluminum lines from which we draw the abundance pattern. Moreover, the photospheric Ca H&K lines are possibly blended with a circumstellar component shifted by \u201320 km s\u20131 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."@en . "10"^^ . "[6FB48315FF2F]" . . . "0004-637X" . . "The Polluted Atmosphere of the White Dwarf NLTT 25792 and the Diversity of Circumstellar Environments" . "Astrophysical Journal" .