相关论文: On mode trapping in pulsating DA white dwarf stars

We demonstrate that plasmon neutrinos are the dominant form of energy loss in model white dwarf stars down to T_eff ~ 25,000 K, depending on the stellar mass. The lower end of this range overlaps the observed temperatures for the V777 Her…

We propose a scenario for the formation of DA white dwarfs with very thin helium buffers. For these stars we explore the possible occurrence of diffusion-induced CNO- flashes, during their early cooling stage. In order to obtain very thin…

We study pattern-forming instabilities in reaction-advection-diffusion systems. We develop an approach based on Lyapunov-Bloch exponents to figure out the impact of a spatially periodic mixing flow on the stability of a spatially…

We find that the radiative diffusivity associated with the radiative viscosity generates a mixing that diminishes the efficiency of the gravitational settling in the external layers of stellar models corresponding to types earlier than G.…

We examine the emergent fluxes from helium-core white dwarfs following their evolution from the end of pre-white dwarf stages down to advanced cooling stages. For this purpose, we include a detailed treatment of the physics of the…

The hydrogen envelope is the outermost layer of a DA white dwarf; it makes up the entirety of the stellar photosphere, and yet its typical extent is difficult to model theoretically and remains poorly observationally constrained. As a…

The effect of diffusion on the chemical composition of subdwarf B (sdB) stars and of hot white dwarfs strongly depends on the presence of weak winds. In the paper, for stars with half a solar mass, for various effective temperatures between…

Some low-mass white-dwarf (LMWD) stars with H atmospheres show long-period g-mode pulsations, comprising the class of pulsating WDs called extremely low-mass variable (ELMV) stars. It is generally believed that these stars have thick H…

Advective trapping occurs when solute enters low velocity zones in heterogeneous porous media. Classical local modeling approaches combine the impact of slow advection and diffusion into a hydrodynamic dispersion coefficient and many…

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 present new and improved evolutionary calculations for carbon-oxygen white dwarf (WD) stars appropriate for the study of massive ZZ Ceti stars. We follow the complete evolution of massive WD progenitors from the zero-age main sequence…

We perform a series of smoothed particle hydrodynamics simulations of isolated dwarf galaxies to compare different metal mixing models. In particular, we examine the role of diffusion in the production of enriched outflows, and in…

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…

The asteroseismic analysis of white dwarfs allows us to peer below their photospheres and determine their internal structure. At ~ 28,000 K EC20058-5234 is the hottest known pulsating helium atmosphere white dwarf. As such, it constitutes…

We present a study of the iron abundance pattern in hot hydrogen-rich (DA) white dwarfs. The study is based on new and archival far ultraviolet spectroscopy of a sample of white dwarfs in the temperature range 30,000 K < T_eff < 64,000 K.…

A large proportion of observed white dwarfs (WDs) show evidence of debris disks, remnants of the former planetary systems, and/or signatures of heavy elements in their atmospheres, induced by the accretion of planetary matter onto their…

Previous work has established that the localized regime of wave transport in open media is characterized by a position-dependent diffusion coefficient. In this work we study how the concept of position-dependent diffusion affects the delay…

Time-dependent injection can cause non-linear cooling effects, which lead to a faster energy loss of the electrons in jets. The most obvious result is the appearance of unique breaks in the SED, which would normally be attributed to a…

We present the first description of mode trapping for sdO models. Mode trapping of gravity modes caused by the He/H chemical transition is found for a particular model, providing a selection effect for high radial order trapped modes. Low-…

We present a set of full evolutionary sequences for white dwarfs with hydrogen-deficient atmospheres. We take into account the evolutionary history of the progenitor stars, all the relevant energy sources involved in the cooling, element…