相关论文: The non-explosive stellar merging origin of the ul…
A population of anomalous ultra-massive white dwarfs discovered with Gaia, often referred to as the Q branch, show high (multi-Gyr) cooling delays produced by exotic physical mechanisms. They are believed to be the products of stellar…
Taking advantage of the Gaia Data Release 2, recent studies have revisited the evolution of carbon-polluted white dwarfs (DQs) across a large range of effective temperatures. These analyses have clearly confirmed the existence of two…
The majority of merging white dwarfs leave behind a white dwarf remnant. Hot/warm DQ white dwarfs with carbon-rich atmospheres have high masses and unusual kinematics. All evidence points to a merger origin. Here, we demonstrate that far-UV…
Hot DQ white dwarfs constitute a new class of white dwarf stars, uncovered recently within the framework of the SDSS project. Recently, three hot DQ white dwarfs have been reported to exhibit photometric variability with periods compatible…
Recent studies of the atmospheres of carbon-rich (DQ) white dwarfs have demonstrated the existence of two different populations that are distinguished by the temperature range, but more importantly, by the extremely high masses of the…
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…
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…
Among the spectroscopically identified white dwarfs, a fraction smaller than 2% have spectra dominated by carbon lines, mainly molecular C2, but also in a smaller group by CI and CII lines. These are together called DQ white dwarfs. We want…
White dwarf stars frequently experience external pollution by heavy elements, and yet the intrinsically carbon-enriched DQ spectral class members fail to exhibit this phenomenon, representing a decades-old conundrum. This study reports a…
We perform stellar evolution calculations of the remnant of the merger of two He white dwarfs (WDs). Our initial conditions are taken from hydrodynamic simulations of double WD mergers and the viscous disc phase that follows. We evolve…
Four years after the discovery of a unique DAQ white dwarf with a hydrogen-dominated and carbon-rich atmosphere, we report the discovery of four new DAQ white dwarfs, including two that were not recognized properly in the literature. We…
Atmospheric carbon has been detected in the optical spectra of six hydrogen-rich ultra-massive white dwarfs, revealing large carbon abundances (log C/H > $-$0.5) attributable to the convective dredge-up of internal carbon into thin hydrogen…
Several hypervelocity white dwarfs (HVWDs) with space velocities of $\gtrsim 1000\,\mathrm{kms}^{-1}$ have recently been discovered. One possible origin of these stars is the dynamically-driven double-degenerate double-detonation (D6)…
Binary systems of two carbon-oxygen white dwarfs are one of the most promising candidates for the progenitor systems of Type Ia supernovae. Violent mergers, where the primary white dwarf ignites when the secondary white dwarf smashes onto…
The merger of two carbon-oxygen white dwarfs can lead either to a spectacular transient, stable nuclear burning or a massive, rapidly rotating white dwarf. Simulations of mergers have shown that the outcome strongly depends on whether the…
White dwarfs are dense, cooling stellar embers consisting mostly of carbon and oxygen, or oxygen and neon (with a few percent carbon) at higher initial stellar masses. These stellar cores are enveloped by a shell of helium which in turn is…
We present an analysis and re-appraisal of the massive, carbon-enriched (DQ) white dwarf (WD) LP 93-21. Its high mass (~1 M_sun) and membership to the class of warm DQ WDs, combined with its peculiar halo kinematics suggest that this object…
Hot white dwarfs with carbon-dominated atmospheres (hot DQs) are a cryptic class of white dwarfs. In addition to their deficiency of hydrogen and helium, most of these stars are highly magnetic, and a large fraction vary in luminosity. This…
Convective overshooting in super asymptotic giant branch stars has been suggested to lead to the formation of hybrid white dwarfs with carbon-oxygen cores and oxygen-neon mantles. As the white dwarf cools, this core-mantle configuration…
Many double white dwarf (WD) mergers likely do not lead to a prompt thermonuclear explosion. We investigate the prospects for observationally detecting the surviving remnants of such mergers, focusing on the case of mergers of double…