Related papers: Hydrogen model atmospheres for white dwarf stars
We present a new, better-constrained asteroseismic analysis of the helium-atmosphere (DB) white dwarf discovered in the field of view of the original Kepler mission. Observations obtained over the course of two years yield at least seven…
(Abridged) We present the results of the first unbiased survey for metal pollution among H-atmosphere (DA) white dwarfs with cooling ages of 20-200 Myr and 17000K < Teff < 27000K, using HST COS in the far UV between 1130 and 1435 A. The…
As part of our laboratory investigation of the theoretical line profiles used in white dwarf atmosphere models, we extend the electron-density ($n_{\rm e}$) range measured by our experiments to higher densities (up to…
We spectroscopically measure multiple hydrogen Balmer line profiles from laboratory plasmas to investigate the theoretical line profiles used in white dwarf atmosphere models. X-ray radiation produced at the Z Pulsed Power Facility at…
We construct a 3D radiative-hydrodynamic model atmosphere of parameters Teff = 4820 K, log g = 4.5, and solar chemical composition. The theoretical line profiles computed with this model are asymmetric, with their bisectors having a…
Our preliminary results from laboratory experiments studying white dwarf (WD) photospheres show a systematic difference between experimental plasma conditions inferred from measured H$\beta$ absorption line profiles versus those from…
The accretion of rocky material is responsible for the presence of heavy elements in the atmospheres of a large fraction of white dwarf stars. Those objects represent a unique opportunity to infer the bulk composition of exoplanetesimals.…
White dwarf studies carry significant implications across multiple fields of astrophysics, including exoplanets, supernova explosions, and cosmological investigations. Thus, accurate determinations of their fundamental parameters (Teff and…
We construct partially ionized hydrogen atmosphere models for magnetized neutron stars in radiative equilibrium with fixed surface fields between B=10^12 and 2x10^13 G and effective temperatures logT_eff=5.5-6.8, as well as with surface B…
We present new determinations of effective temperature, surface gravity, and masses for a sample of 46 hot DA white dwarfs selected from the EUVE and ROSAT Wide Field Camera bright source lists in the course of a near-IR survey for low mass…
We report our findings on a spectroscopic survey of seven unresolved DA+DB binary white dwarf candidates. We have discovered extreme spectroscopic variations in one of these candidates, SDSS J084716.21+484220.40. Previous analysis failed to…
The hydrogen envelope is the outermost layer of a DA white dwarf; it makes up the entirety of the stellar photosphere, and yet its typical extent is difficult to model theoretically and remains poorly observationally constrained. As a…
Observed X-ray spectra of some isolated magnetized neutron stars display absorption features, sometimes interpreted as ion cyclotron lines. Modeling the observed spectra is necessary to check this hypothesis and to evaluate neutron star…
We present a comprehensive analysis of DB white dwarfs drawn from the Sloan Digital Sky Survey, based on model fits to $ugriz$ photometry and medium resolution spectroscopy from the SDSS. We also take advantage of the exquisite…
White dwarf and pre-white dwarf atmospheres are one of the best examples for the application of Stark broadening research results in astrophysics, due to plasma conditions very favorable for this line broadening mechanism. For example in…
We report the discovery of spectroscopic variations in GD 323, the prototypical DAB white dwarf. Simultaneous optical spectroscopic observations over five consecutive nights of GD 323 and of PG 1234+482, a non-variable comparison DA white…
We present a new set of solar metallicity atmosphere and evolutionary models for very cool brown dwarfs and self-luminous giant exoplanets, which we term ATMO 2020. Atmosphere models are generated with our state-of-the-art 1D…
The recent plethora of sky surveys, especially the Sloan Digital Sky Survey, have discovered many low-mass (M < 0.45 Msun) white dwarfs that should have cores made of nearly pure helium. These WDs come in two varieties; those with masses…
A selection of 17 stars in the Sloan Digital Sky Survey, previously identified as DC class white dwarfs (WDs), has been reported to show spectra very close to blackbody radiation in the wavelength range from ultraviolet to infrared. Due to…
We present a comparative analysis of atmospheric parameters obtained with the so-called photometric and spectroscopic techniques. Photometric and spectroscopic data for 1360 DA white dwarfs from the Sloan Digital Sky Survey (SDSS) are used,…