We provide a fine and homogeneous grid of evolutionary sequences for He-core white dwarfs with masses 0.15-0.45 Msun, including the mass range ELM (<0.20Msun). The is appropriate age determination, to study their pulsational properties. White dwarf have been computed by performing full calculations that consider main energy sources processes chemical abundance changes during evolution. Initial models evolving obtained computing non-conservative evolution binary system consisting Msun ZAMS...

We explore the formation and evolution of hydrogen-deficient post-AGB white dwarfs. To this end, we compute complete an initially star from zero-age main sequence through thermally pulsing mass-loss phases to dwarf stage. Particular attention is given chemical abundance changes during whole evolution. A time-dependent scheme for simultaneous treatment caused by nuclear reactions, diffusive overshooting, salt fingers convection considered. employed double-diffusive mixing-length theory fluids...

We present full evolutionary calculations appropriate for the study of hydrogen-rich DA white dwarfs. This is done by evolving dwarf progenitors from zero age main sequence, through core hydrogen burning phase, helium phase and thermally pulsing asymptotic giant branch to stage. Complete sequences are computed a wide range stellar masses two different metallicities: Z=0.01, which representative solar neighborhood, Z=0.001, old systems, like globular clusters. During cooling stage we compute...

High-field magnetic white dwarfs have been long suspected to be the result of stellar mergers. However, nature coalescing stars and precise mechanism that produces field are still unknown. Here, we show hot, convective, differentially rotating corona present in outer layers remnant merger two degenerate cores can produce fields required strength do not decay for timescales. Using a state-of-the-art Monte Carlo simulator, also expected number high-field produced this way is consistent with...

Ultra-massive white dwarfs are powerful tools to study various physical processes in the Asymptotic Giant Branch (AGB), type Ia supernova explosions and theory of crystallization through dwarf asteroseismology. Despite interest these dwarfs, there few evolutionary studies literature devoted them. Here, we present new ultra-massive sequences that constitute an improvement over previous ones. In sequences, take into account for first time process phase separation expected during stage by...

We present new white dwarf evolutionary sequences for low-metallicity progenitors. White have been derived from full calculations that take into account the entire history of progenitor stars, including thermally-pulsing and post-asymptotic giant branch phases. show metallicities in range 0.00003--0.001, absence carbon enrichment due to occurrence a third dredge-up episode, resulting H envelope low-mass dwarfs is thick enough make stable burning most important energy source even at low...

We employ a state-of-the-art asteroseismological model of G117-B15A, the archetype H-rich atmosphere (DA) white dwarf pulsators (also known as DAV or ZZ Ceti variables), and use most recently measured value rate period change for dominant mode this pulsating star to derive new constraint on mass axion, still conjectural non-barionic particle considered candidate dark matter Universe. Assuming that G117-B15A is truly represented by our model, in particular, associated pulsation g-mode trapped...

White dwarf stars are the most common end point of stellar evolution. Of special interest ultramassive white dwarfs, as they related to type Ia Supernovae explosions, merger events, and Fast Radio Bursts. Ultramassive dwarfs expected harbour oxygen-neon (ONe) cores a result single standard However, fraction them could have carbon-oxygen (CO) cores. Recent studies, based on new observations provided by {\it Gaia} space mission, indicate that small experience strong delay in their cooling,...

This submission has been removed by arXiv administrators because it is a duplicate of astro-ph/0603735.

We present evolutionary calculations and colors for massive white dwarfs with oxygen-neon cores masses between 1.06 1.28 Mo. The stages computed cover the luminosity range from log(L/Lo) approx. 0.5 down to -5.2. Our cooling sequences are based on that take into account chemical composition expected dwarf progenitors burned carbon in partially degenerate conditions. use of detailed non-gray model atmospheres provides us accurate outer boundary conditions our evolving models at low effective...

ABSTRACT Because of the large neutron excess 22 Ne, sedimentation this isotope occurs rapidly in interior white dwarfs. This process releases an additional amount energy, thus delaying cooling times dwarf. influences ages different stellar populations derived using dwarf cosmochronology. Furthermore, overabundance Ne inner regions star modifies Brunt–Väisälä frequency, altering pulsational properties these stars. In work we discuss impact dwarfs resulting from solar metallicity progenitors (...

We present optical high-speed photometry of three millisecond pulsars with low-mass (<0.3 M⊙) white dwarf companions, bringing the total number such systems follow-up time-series to five. confirm detection pulsations in one system, companion PSR J1738+0333, and show that pulsation frequencies amplitudes are variable over many months. A full asteroseismic analysis for this star is underconstrained, but mode periods we observe consistent expectations an |$M_{\star }=0.16 - 0.19\,M_{\odot }$|...

We use the data provided by Gaia Early Data Release 3 to search for a highly-complete volume-limited sample of unresolved binaries consisting white dwarf and main sequence companion (i.e. WDMS binaries) within 100pc. select 112 objects based on their location Hertzsprung-Russell diagram, which 97 are new identifications. fit spectral energy distributions (SED) with two-body fitting algorithm implemented in VOSA (Virtual Observatory SED Analyser) derive effective temperatures, luminosities...

We reexamine the theoretical instability domain of pulsating PG1159 stars (GW Vir variables). performed an extensive g-mode stability analysis on evolutionary models with stellar masses ranging from 0.530 to 0.741 Mo for which complete stages their progenitors ZAMS, through thermally pulsing AGB and born-again phases have been considered. found that pulsations in are excited by kappa-mechanism due partial ionization carbon oxygen, no composition gradients needed between surface layers...

We present detailed theoretical mass-radius relations for massive white dwarf stars with oxygen-neon cores. This work is motivated by recent observational evidence about the existence of very high surface gravities. Our results are based on evolutionary calculations that take into account chemical composition expected from history progenitors. stellar mass values ranging 1.06 to 1.30 Mo a step 0.02 and effective temperatures 150000 K approx. 5,000 K. A novel aspect predicted our relation...

A distributed, serotonergically innervated neural system comprising extrastriate cortex, amygdala and ventral prefrontal cortex is critical for identification of socially relevant emotive stimuli. The extent to which a genetic variation serotonin transporter gene 5-HTTLPR impacts functional connectivity between the other components this remains little examined. In our study, activity was measured using event-related magnetic resonance imaging in 29 right-handed, white Caucasian healthy...

Axions are the natural consequence of introduction Peccei-Quinn symmetry to solve strong CP problem. All efforts detect such elusive particles have failed up now. Nevertheless, it has been recently shown that luminosity function white dwarfs is best fitted if axions with a mass few meV included in evolutionary calculations. Our aim show variable can provide additional and independent evidence about existence axions. The evolution dwarf slow cooling process translates into secular increase...

We present full evolutionary calculations appropriate for the study of hot hydrogen-deficent DO white dwarfs, PG 1159 stars, and DB dwarfs. White dwarf sequences are computed a wide range stellar masses helium envelopes on basis complete treatment history progenitors including core hydrogen burning phases, thermally-pulsing AGB phase, born-again episode that is responsible deficiency. also provide colors magnitudes new $T_{\rm eff} < 40 000$ K, where NLTE effects not dominant. These an...

Pulsating white dwarfs with hydrogen-rich atmospheres, also known as DAV stars, can be used astrophysical laboratories to constrain the properties of fundamental particles like axions. Comparing measured cooling rates these stars expected values from theoretical models allows us search for sources additional due emission weakly interacting particles. In this paper, we present an independent inference mass axion using recent determination evolutionary rate R548, class prototype. We employ a...

The Peccei-Quinn mechanism proposed to solve the CP problem of Quantum Chromodynamics has as consequence existence axions, hypothetical weakly interacting particles whose mass is constrained be on sub-eV range. If these exist and interact with electrons, they would emitted from dense interior white dwarfs, becoming an important energy sink for star. Due their well known physics, dwarfs are good laboratories study properties fundamental such axions. We general effect axion emission evolution...