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Many isolated, old white dwarfs (WDs) show surprising evidence of metals in their photospheres. Given that the timescale for gravitational sedimentation is astronomically short, this is taken as evidence for ongoing accretion, likely of…
Novae are cataclysmic variable binary systems in which a white dwarf primary is accreting material from a low mass companion. The importance of this accretion takes on added significance if the WD can increase its mass to reach the…
It is predicted that orbital decay by gravitational-wave radiation and tidal interaction will cause some close-binary stars to merge within a Hubble time. The merger of a helium-core white dwarf with a main-sequence star can produce a red…
Using 2D and 3D simulation, we study the "robustness" of the double detonation scenario for Type Ia supernovae, in which a detonation in the helium shell of a carbon-oxygen white dwarf induces a secondary detonation in the underlying core.…
The progenitors of Type Ia Supernovae (SNe Ia) are still unknown, despite significant progress during the last years in theory and observations. Violent mergers of two carbon--oxygen (CO) white dwarfs (WDs) are one candidate suggested to be…
We investigate the effects of rotation on the behavior of the helium burning shell source in accreting carbon-oxygen white dwarfs, in the context of the single degenerate Chandrasekhar mass progenitor scenario for Type Ia supernovae (SNe…
Once carbon--oxygen white dwarfs cool sufficiently, they crystallize from the inside out. If the white dwarf is rich enough in ${}^{22}\mathrm{Ne}$, these crystallized solids are buoyant and rapidly rise, efficiently liberating potential…
We present three-dimensional simulations on a new mechanism for the detonation of a sub-Chandrasekhar CO white dwarf in a dynamically unstable system where the secondary is either a pure He white dwarf or a He/CO hybrid. For dynamically…
The double detonation model is one of the prevalent explosion mechanisms of Type Ia Supernovae (SNe Ia) wherein an outer helium shell detonation triggers a core detonation in the white dwarf (WD). The dynamically driven double degenerate…
The feasibility of the Double Detonation mechanism, -a surface Helium-detonation followed by the complete carbon detonation of the core-, in a rotating white dwarf with a mass $\simeq 1 M_{\odot}$ is studied using three-dimensional…
We investigate the evolution of cooling helium atmosphere white dwarfs using a full evolutionary code, specifically developed for following the effects of element diffusion and gravitational settling on white dwarf cooling. The major…
Type Ia supernovae (SNe Ia) are common luminous astrophysical transients. SNe Ia serve as distance indicators for measuring the expansion rate of the universe and play important roles in galactic nucleosynthesis. However, ambiguities…
We present the discovery of a new double detonation progenitor system consisting of a hot subdwarf B (sdB) binary with a white dwarf companion with an P=76.34179(2) min orbital period. Spectroscopic observations are consistent with an sdB…
We analyze temporal evolution of the number of accreting white dwarfs with shell hydrogen burning in semidetached and detached binaries. We consider a stellar system in which star formation lasts for 10 Gyr with a constant rate, as well as…
Recent discovery of several overluminous type Ia supernovae (SNe Ia) indicates that the explosive masses of white dwarfs may significantly exceed the canonical Chandrasekhar mass limit. Rapid differential rotation may support these massive…
The origins of type Ia supernovae (SNe Ia) are still debated. Some of the leading scenarios involve a double detonation in double white dwarf (WD) systems. In these scenarios, helium shell detonation occurs on top of a carbon-oxygen (CO)…
We revisit the properties of white dwarfs accreting hydrogen-rich matter by constructing steady-state models, in which hydrogen shell burning consumes hydrogen at the same rate as the white dwarf accretes it. We obtain such steady-state…
We explore the outcome of mass transfer via Roche lobe overflow (RLOF) of $M_{\rm He}\lesssim0.51 M_\odot$ pure helium burning stars in close binaries with white dwarfs (WDs). The evolution is driven by the loss of angular momentum through…
We calculated a grid of evolutionary models for white dwarfs with helium cores (He-WDs) and investigated the occurrence of hydrogen-shell flashes due to unstable hydrogen burning via CNO cycling. Our calculations show that such thermal…
A non negligible fraction of white dwarf stars show the presence of heavy elements in their atmospheres. The most accepted explanation for this contamination is the accretion of material coming from tidally disrupted planetesimals, which…