相关论文: Phase Separation in Ultramassive White Dwarfs
We investigate phase separation in oxygen-neon (O/Ne) ultramassive white dwarfs (UMWDs). Current stellar evolution codes, such as MESA, only account for $\mathrm{^{16}O/^{20}Ne}$ separation and do not include other minor species. To improve…
The precise astrometric measurements of the Gaia Data Release 2 have opened the door to detailed tests of the predictions of white dwarf cooling models. Significant discrepancies between theory and observations have been identified, the…
Ultra-massive white dwarfs ($ 1.05 \rm M_\odot \lesssim M_{WD}$) are particularly interesting objects that allow us to study extreme astrophysical phenomena such as type Ia supernovae explosions and merger events. Traditionally,…
Ultra-massive white dwarfs ($\rm M_{WD} \gtrsim 1.05\, M_{\odot}$) are considered powerful tools to study type Ia supernovae explosions, merger events, the occurrence of physical processes in the Super Asymptotic Giant Branch (SAGB) phase,…
When white dwarfs freeze the plasma mixtures inside them undergo separation processes which can produce radical changes in the composition profile of the star. The abundance of neutron rich elements, such as $^{22}$Ne or $^{56}$Fe,…
Recent computations of the interior composition of ultra-massive white dwarfs (WD) have suggested that some white dwarfs could be composed of neon (Ne)-dominated cores. This result is at variance with our previous understanding of the…
The continuous cooling of a white dwarf is punctuated by events that affect its cooling rate. Probably the most significant of those is the crystallization of its core, a phase transition that occurs once the C/O interior has cooled down…
Accurate phase diagrams of multicomponent plasmas are required for the modeling of dense stellar plasmas, such as those found in the cores of white dwarf stars and the crusts of neutron stars. Those phase diagrams have been computed using a…
Cool white dwarfs are reliable and independent stellar chronometers. The most common white dwarfs have carbon-oxygen dense cores. Consequently, the cooling ages of very cool white dwarfs sensitively depend on the adopted phase diagram of…
White dwarf stars are the most common end point of stellar evolution. Of special interest are the ultramassive white dwarfs, as they are related to type Ia Supernovae explosions, merger events, and Fast Radio Bursts. Ultramassive white…
The 3-body crystallization diagrams of C/O/Ne ionic mixtures characteristic of white dwarf interiors are examined within the framework of the density-functional theory of freezing. The crystallization process is described more accurately…
Accurate models of cooling white dwarfs must treat the energy released as their cores crystallize. This phase transition slows the cooling by releasing latent heat and also gravitational energy, which results from phase separation: liquid C…
Ultra-massive hydrogen-rich white dwarfs (WDs) stars are expected to harbor oxygen/neon cores resulting from semi-degenerate carbon burning when the progenitor star evolves through the super asymptotic giant branch (SAGB) phase. These stars…
Ultra-massive white dwarfs are powerful tools to study various physical processes in the Asymptotic Giant Branch (AGB), type Ia supernova explosions and the theory of crystallization through white dwarf asteroseismology. Despite the…
We present follow-up spectroscopy and a detailed model atmosphere analysis of 29 wide double white dwarfs, including eight systems with a crystallized C/O core member. We use state-of-the-art evolutionary models to constrain the physical…
Ultramassive white dwarfs with masses $M\gtrsim 1.1\,{\rm M}_\odot$ probe extreme physics near the Chandrasekhar limit. Despite the rapid increase in observations, it is still unclear how many harbour carbon-oxygen (CO) versus oxygen-neon…
We enhance the treatment of crystallization for models of white dwarfs (WDs) in the stellar evolution software MESA by implementing carbon-oxygen (C/O) phase separation. The phase separation process during crystallization leads to transport…
Recent observations of Galactic white dwarfs (WDs) with Gaia suggest there is a population of massive crystallizing WDs exhibiting anomalous cooling -- the Q branch. While single-particle $^{22}$Ne sedimentation has long been considered a…
Ultra-massive hydrogen-rich (DA spectral type) white dwarf (WD) stars ($M_{\star} > 1M_{\odot}$) coming from single-star evolution are expected to harbor cores made of $^{16}$O and $^{20}$Ne, resulting from semi-degenerate carbon burning…
A hybrid C/O/Ne white dwarf (WD) -- an unburned C/O core surrounded by an O/Ne/Na mantle -- can be formed if the carbon flame is quenched in a super-AGB (SAGB) star or white dwarf merger remnant. We show that this segregated hybrid…