![]() ![]() Convective overshoot and macroscopic diffusion in pure-hydrogen-atmosphere white dwarfs. ![]() Accretion and diffusion in white dwarfs: new diffusion timescales and applications to GD 362 and G 29-38. New phase diagrams for dense carbon–oxygen mixtures and white dwarf evolution. G., García-Berro, E., Isern, J., Córsico, A. A proposed new white dwarf spectral classification system. The highly collapsed configurations of a stellar mass (second paper). Gaia Data Release 2: summary of the contents and survey properties. A Gaia Data Release 2 catalogue of white dwarfs and a comparison with SDSS. A massive white-dwarf merger product before final collapse. A cooling anomaly of high-mass white dwarfs. ![]() The long-term evolution of double white dwarf mergers. Supernova type Ia progenitors from merging double white dwarfs: using a new population synthesis model. Asymptotic giant branch evolution and beyond. On the spectral evolution of helium-atmosphere white dwarfs showing traces of hydrogen. Carbon-rich (DQ) white dwarfs in the Sloan Digital Sky Survey. Analysis of helium-rich white dwarfs polluted by heavy elements in the Gaia era. Carbon pollution in helium-rich white dwarf atmospheres: time-dependent calculations of the dredge-up process. Pelletier, C., Fontaine, G., Wesemael, F., Michaud, G. Atmospheric parameters and carbon abundance of white dwarfs of spectral types C2 and DC. White dwarf and subdwarf stars in the Sloan Digital Sky Survey Data Release 14. The evolution of ultra-massive white dwarfs. Stellar evolution from main sequence to white dwarf or carbon ignition. Due to the fast kinematics (129 ± 5 km s −1 relative to the local standard of rest), large mass and peculiar envelope composition, we argue that WD J0551+4135 is consistent with formation from the merger of two white dwarfs in a tight binary system 11, 12, 13, 14. Our analysis of the envelope and interior indicates that the total hydrogen and helium mass fractions must be several orders of magnitude lower than predictions of single-star evolution 10: less than 10 −9.5 and 10 −7.0, respectively. We report the identification of WD J055134.612+413531.09, an ultra-massive (1.14 solar masses ( M ⊙)) white dwarf with a unique carbon–hydrogen mixed atmosphere (atomic ratio C∕H = 0.15). In these objects, only traces of hydrogen are found 7, 8, as large masses of hydrogen are predicted to inhibit hydrogen–helium convective mixing within the envelope 9. However, carbon is observed at the surface of a sizeable fraction of white dwarfs 3, 4, sometimes with traces of oxygen, and is thought to be dredged up from the core by a deep helium convection zone 5, 6. These stellar cores are enveloped by a shell of helium, which in turn, is usually surrounded by a layer of hydrogen, generally prohibiting direct observation of the interior composition. White dwarfs are dense, cooling stellar embers consisting mostly of carbon and oxygen 1, or oxygen and neon (with a few per cent carbon) at higher initial stellar masses 2. ![]()
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