Related papers: Equilibrium abundances in hot DA white dwarfs as d…
We compare measured element abundances in hot DA white dwarfs from UV observations to predictions from our self-consistent non-LTE model atmosphere diffusion calculations.
The presence of heavy elements in the atmospheres of the hottest H-rich DA white dwarfs has been the subject of considerable interest. While theoretical calculations can demonstrate that radiative forces, counteracting the effects of…
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 present a detailed calculation of model atmospheres for DA white dwarfs. Our atmosphere code solves the atmosphere structure in local thermodynamic equilibrium with a standard partial linearization technique, which takes into account the…
We present a series of systematic abundance measurements for 89 hydrogen atmosphere (DA-type) white dwarfs with temperatures spanning 16000-77000K drawn from the FUSE spectral archive. This is the largest study to date of white dwarfs where…
Large Gaia data set shows substantial misfit between models and observation for cool white dwarfs with $T_{\rm eff}<6000\,\rm K$, resulting in severe underestimation of masses of these stars. We aim to understand the underlying modelling…
We have obtained new optical and extreme ultraviolet (EUV) spectroscopy of the ultramassive white dwarf EUVE J1746-706. We revise Vennes et al.'s (1996a, ApJ, 467, 784) original estimates of the atmospheric parameters and we measure an…
Atmospheric parameters for hot DB (helium atmosphere) white dwarfs near effective temperatures of 25000K are extremely difficult to determine from optical spectroscopy. This is particularly unfortunate, because this is the range of variable…
Over the last decade {\it ab initio} modeling of material properties has become widespread in diverse fields of research. It has proved to be a powerful tool for predicting various properties of matter under extreme conditions. We apply…
We present a new generation of substellar atmosphere and evolution models, appropriate for application to studies of L, T, and Y-type brown dwarfs and self-luminous extrasolar planets. The atmosphere models describe the expected…
The surface gravities of cool (Teff < 13,000 K) hydrogen-atmosphere DA white dwarfs, determined from spectroscopic analyses, are found to be significantly higher than the canonical value of log g ~ 8 expected for these stars. It was…
We present the first grid of mean three-dimensional (3D) spectra for pure-hydrogen (DA) white dwarfs based on 3D model atmospheres. We use CO5BOLD radiation-hydrodynamics 3D simulations instead of the mixing-length theory for the treatment…
Reliable modeling of the atmospheres of cool white dwarfs is crucial for understanding the atmospheric evolution of these stars and for accurate white dwarfs cosmochronology. Over the last decade {\it ab initio} modeling entered many…
We present a series of systematic abundance measurements for a group of hot DA white dwarfs in the temperature range 20,000-75,000K, based on far-UV spectroscopy with STIS on HST, IUE and FUSE. Using our latest heavy element blanketed…
We present a study of the iron abundance pattern in hot hydrogen-rich (DA) white dwarfs. The study is based on new and archival far ultraviolet spectroscopy of a sample of white dwarfs in the temperature range 30,000 K < T_eff < 64,000 K.…
We present a LTE model atmosphere analysis of the medium and long wavelength spectrum of the cool DO white dwarf HD149499B. This observation in the spectral range 230-700 A supplements a previous analysis of an ORFEUS spectrum between 912…
The photospheres of the coolest helium-atmosphere white dwarfs are characterized by fluid-like densities. Under those conditions, standard approximations used in model atmosphere codes are no longer appropriate. Unfortunately, the majority…
We present improved atmospheric parameters of nearby white dwarfs lying within 20 pc of the Sun. The aim of the current study is to obtain the best statistical model of the least-biased sample of the white dwarf population. A homogeneous…
Due to their high photospheric density, cool helium-rich white dwarfs (particularly DZ, DQpec and ultracool) are often poorly described by current atmosphere models. As part of our ongoing efforts to design atmosphere models suitable for…
As a result of competing physical mechanisms, the atmospheric composition of white dwarfs changes throughout their evolution, a process known as spectral evolution. Because of the ambiguity of their atmospheric compositions and the…