Adela Kawka, Stephane Vennes
We present a model atmosphere analysis of cool hydrogen-rich white dwarfs
observed at the Very Large Telescope (VLT) with the X-shooter spectrograph. The
intermediate-dispersion and high signal-to-noise ratio of the spectra allowed
us to conduct a detailed analysis of hydrogen and heavy element line profiles.
In particular, we tested various prescriptions for hydrogen Balmer line
broadening parameters and determined the effective temperature and surface
gravity of each star. Three objects (NLTT 1675, 6390 and 11393) show the
presence of heavy elements (Mg, Al, Ca, or Fe). Our abundance analysis revealed
a relatively high iron to calcium ratio in NLTT 1675 and NLTT 6390. We also
present an analysis of spectropolarimetric data obtained at the VLT using the
focal reducer and low dispersion spectrograph (FORS) and we established strict
upper limits on the magnetic field strengths in three of the DAZ white dwarfs
and determined the longitudinal magnetic field strength in the DAZ NLTT 10480.
The class of DAZ white dwarfs comprises objects that are possibly accreting
material from their immediate circumstellar environment and the present study
contributes in establishing class properties.
View original:
http://arxiv.org/abs/1111.3250
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