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White dwarfs which exhibit transit signatures of planetary debris and accreted planetary material provide exceptional opportunities to probe the material composition and dynamical structure of planetary systems. Although previous…
Many isolated white dwarfs (WDs) show spectral evidence of atmospheric metal pollution. Since heavy element sedimentation timescales are short, this most likely indicates ongoing accretion. Accreted metals encounter a variety of mixing…
A large fraction of white dwarf stars shows photospheric chemical composition polluted by heavy elements accreted from a debris disk. Such debris disks result from the tidal disruption of rocky planetesimals which had survived to whole…
The diffusion of elements is a key process in understanding the unusual surface composition of white dwarfs stars and their spectral evolution. The diffusion coefficients of Paquette et al. (1986) have been widely used to model diffusion in…
We use the most recent, complete and independent measurements of masses and radii of white dwarfs in binaries to bound the class of non-trivial modified gravity theories, viable after GW170817/GRB170817, using its effect on the mass-radius…
Thermal evolution of the central region of a $0.9 \, M_\odot$ C/O white dwarf at the initial stage of the ion mixture crystallization is studied by numerically solving the heat equation on a fine spatial and temporal grid and by including a…
We present new cooling sequences, color-magnitude diagrams, and color-color diagrams for cool white dwarfs with pure hydrogen atmospheres down to an effective temperature $\te=1500$ K. We include a more detailed treatment of the physics of…
We investigate heat transport associated with compositionally-driven convection driven by crystallization at the ocean-crust interface in accreting neutron stars, or growth of the solid core in cooling white dwarfs. We study the effect of…
We investigate the structure and stability against radial oscillations, pycnonuclear reactions, and inverse $\beta$-decay of hot white dwarfs. We regard that the fluid matter is made up for nucleons and electrons confined in a Wigner-Seitz…
This letter reports statistically significant changes in the equivalent widths of MgII and CaII lines in the dusty and polluted white dwarf WD 0106-328, based on six epochs of spectroscopy using the VLT and Keck spanning 25 yr. Furthermore,…
We investigate the evolution of isolated, zero and finite temperature, massive, uniformly rotating and highly magnetized white dwarf stars under angular momentum loss driven by magnetic dipole braking. We consider the structure and thermal…
We calculate the stellar evolution of both white dwarfs (WDs) in AM CVn binaries with orbital periods of $P_{\mathrm{orb}} \approx 5-70$ minutes. We focus on the cases where the donor starts as a $M_{\mathrm{He}} < 0.2 \, M_{\odot}$ Helium…
The diffusion coefficients of neutron rich nuclei in crystallizing white dwarf (WD) stars are essential microphysics input for modeling the evolution of the composition profile. Recently, molecular dynamics simulations have been used to…
Two low-mass pre-white dwarfs, which could be precursors of ELM white dwarfs, have been observed to show multiperiodic photometric variations. They could constitute a new class of pulsating low-mass pre-white dwarf stars. We present a…
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…
Polluted white dwarfs serve as astrophysical mass spectrometers - their photospheric abundances are used to infer the composition of planetary objects that accrete onto them. We show that due to asymmetries in the accretion process, the…
Approximately 25--50\% of white dwarfs (WDs) exhibit metal absorption lines in their photospheres, interpreted as evidence of ongoing/recent accretion of planetary debris from remnant systems. Previous theoretical studies have suggested…
We investigate crystallization-driven convection in carbon-oxygen white dwarfs. We present a version of the mixing length theory (MLT) that self-consistently includes the effects of thermal diffusion and composition gradients, and provides…
Abridged. White dwarf stars are the final evolutionary stage of the vast majority of stars, including our Sun. The study of white dwarfs has potential applications to different fields of astrophysics. In particular, they can be used as…
In the framework of our extensive modeling study of the spectral evolution of white dwarfs, we present here a new set of detailed calculations of the transport of residual hydrogen in helium-rich white dwarfs. First, we investigate the…