Related papers: Evolutionary sequences for hydrogen-deficient whit…
Diffusion of elements in the atmosphere and envelope of a star can drastically alter its surface composition, leading to extreme chemical peculiarities. We consider the case of hot subdwarfs, where surface helium abundances range from…
We provide a fine and homogeneous grid of evolutionary sequences for He-core white dwarfs with masses 0.15-0.45 Msun, including the mass range for ELM white dwarfs (<0.20Msun). The grid is appropriate for mass and age determination, and to…
White dwarf stars are subject to various element transport mechanisms that can cause their surface composition to change radically as they cool, a phenomenon known as spectral evolution. In this paper, we undertake a comprehensive…
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…
White Dwarfs (WDs) are the final evolutionary product of the vast majority of stars in the Universe. They are electron-degenerate structures characterized by no stable thermonuclear activity, and their evolution is generally described as a…
We study the structure and evolution of white dwarf stars with helium-rich atmospheres (DB) in a self-consistent way with the predictions of time-dependent element diffusion. Our treatment of diffusion includes gravitational settling and…
White dwarfs, the extremely dense remnants left behind by most stars after their death, are characterised by a mass comparable to that of the Sun compressed into the size of an Earth-like planet. In the resulting strong gravity, heavy…
Cool white dwarfs with Teff < 6000 K are the remnants of the oldest stars that existed in our Galaxy. Their atmospheres, when properly characterized, can provide valuable information on white dwarf evolution and ultimately star formation…
A detailed analysis of the very cool white dwarfs SDSS 1337+00 and LHS 3250 is presented. Model atmosphere calculations with improved collision-induced absorptions by molecular hydrogen indicate that a pure hydrogen composition can be ruled…
White dwarfs are the final remnants of low- and intermediate-mass stars. Their evolution is essentially a cooling process that lasts for $\sim 10$ Gyr. Their observed properties provide information about the history of the Galaxy, its dark…
The atmospheres of cool, helium-rich white dwarfs constitute an exotic and poorly explored physical regime of stellar atmospheres. Under physical conditions where the temperature varies from $\rm 1000K$ to $\rm 10000K$, the density can…
We present the first full evolutionary calculations aimed at exploring the origin of hot DQ white dwarfs. These calculations consistently cover the whole evolution from the born-again stage to the white dwarf cooling track. Our calculations…
The Gaia colour--magnitude diagram reveals a striking separation between hydrogen-atmosphere white dwarfs and their helium-atmosphere counterparts throughout a significant portion of the white dwarf cooling track. However, pure-helium…
In the absence of a third dredge-up episode during the asymptotic giant branch phase, white dwarf models evolved from low-metallicity progenitors have a thick hydrogen envelope, which makes hydrogen shell burning be the most important…
We present the first grid of 3D simulations for the pure-helium atmospheres of DB white dwarfs. The simulations were computed with the CO5BOLD radiation-hydrodynamics code and cover effective temperatures and surface gravities between 12000…
Hydrogen deficient stars include the cool R CrB variable (RCBs) and hydrogen-deficient carbon (HdCs) giants through extreme helium stars (EHes) to the very hot helium-rich subdwarfs (He-sdO and O(He) stars) and white dwarfs. With surfaces…
The photospheric metal pollution of white dwarfs is now well-established as the signature of the accretion of planetary debris. However, the origin of the trace hydrogen detected in many white dwarfs with helium atmospheres is still…
White dwarfs are almost completely degenerate objects that cannot obtain energy from thermonuclear sources, so their evolution is just a gravothermal cooling process. Recent improvements in the accuracy and precision of the luminosity…
We report new infrared spectroscopic observations of cool DQ white dwarfs by using Coolspec on the 2.7m Harlan-Smith Telescope. DQs have helium-rich atmospheres with traces of molecular carbon thought to be the result of convective…
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…