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We have found that at least seven hydrogen-deficient carbon (HdC) and R Coronae Borealis (RCB) stars, have 16O/18O ratios close to and in some cases less than unity, values that are orders of magnitude lower than measured in other stars…

If accreting white dwarfs (WD) in binary systems are to produce type Ia supernovae (SNIa), they must grow to nearly the Chandrasekhar mass and ignite carbon burning. Proving conclusively that a WD has grown substantially since its birth is…

Solar and Stellar Astrophysics · Physics 2017-10-04 Joanna Mikolajewska , Michael M. Shara

We perform stellar evolution calculations of the remnant of the merger of two He white dwarfs (WDs). Our initial conditions are taken from hydrodynamic simulations of double WD mergers and the viscous disc phase that follows. We evolve…

Solar and Stellar Astrophysics · Physics 2018-03-21 Josiah Schwab

The detection of pulsations in white dwarfs with low mass offers the possibility of probing their internal structure through asteroseismology and place constraints on the binary evolutionary processes involved in their formation. In this…

Solar and Stellar Astrophysics · Physics 2015-06-22 A. H. Córsico , L. G. Althaus

We have computed the physical processes involved in a head-on collision between a neutron star (NS) and a white dwarf (WD). The outcomes of such collisions vary depending on the mass and type of the WD. We have separately examined the…

High Energy Astrophysical Phenomena · Physics 2025-12-10 Zong-kai Peng , He Gao , Xian-Fei Zhang

In binary systems, the helium accretion onto carbon-oxygen (CO) white dwarfs (WDs) plays a vital role in many astrophysical scenarios, especially in supernovae type Ia. Moreover, ignition density for accretion rate $\dot{M} \lesssim 10^{-9}…

Solar and Stellar Astrophysics · Physics 2021-11-29 Harish Kumar , Abhinav Gupta , Siddharth Savyasachi Malu , Shashikant Gupta

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…

Astrophysics · Physics 2007-05-23 T. Driebe , T. Bloecker , D. Schoenberner , F. Herwig

Sub-Chandrasekhar mass carbon-oxygen white dwarfs (CO WDs) with a surface helium (He) shell have been proposed as progenitors of Type Ia supernovae (SNe Ia). If true, the resulting thermonuclear explosions should be able to account for at…

Solar and Stellar Astrophysics · Physics 2021-06-08 Sabrina Gronow , Christine E. Collins , Stuart A. Sim , Friedrich K. Roepke

Recently, a new class of white dwarfs (``slowly cooling WDs'') has been identified in the globular cluster M13. The cooling time of these stars is increased by stable thermonuclear hydrogen burning in their residual envelope. These WDs are…

Solar and Stellar Astrophysics · Physics 2022-08-03 J. Chen , F. R. Ferraro , M. Cadelano , M. Salaris , B. Lanzoni , C. Pallanca , L. G. Althaus , S. Cassisi , E. Dalessandro

We determine the phase diagram for dense carbon/ oxygen mixtures in White Dwarf (WD) star interiors using molecular dynamics simulations involving liquid and solid phases. Our phase diagram agrees well with predictions from Ogata et al. and…

Solar and Stellar Astrophysics · Physics 2014-11-21 C. J. Horowitz , A. S. Schneider , D. K. Berry

Context: Superluminous type Ia supernovae (SNe Ia) may be explained by super-Chandrasekhar-mass explosions of rapidly rotating white dwarfs (WDs). In a preceding paper, we showed that the deflagration scenario applied to rapidly rotating…

High Energy Astrophysical Phenomena · Physics 2015-05-14 J. M. M. Pfannes , J. C. Niemeyer , W. Schmidt

We have studied double-detonation explosions in double-degenerate (DD) systems with different companion white dwarfs (WD) for modeling type Ia supernovae (SNe Ia) by means of high-resolution smoothed particle hydrodynamics (SPH)…

High Energy Astrophysical Phenomena · Physics 2019-11-26 Ataru Tanikawa , Ken'ichi Nomoto , Naohito Nakasato , Keiichi Maeda

The convective dredge-up of carbon from the interiors of hydrogen-deficient white dwarfs has long been invoked to explain the presence of carbon absorption features in the spectra of cool DQ stars ($T_{\rm eff} < 10{,}000\,{\rm K}$). It has…

Solar and Stellar Astrophysics · Physics 2023-08-09 Simon Blouin , Mukremin Kilic , Antoine Bédard , Pier-Emmanuel Tremblay

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…

High Energy Astrophysical Phenomena · Physics 2015-05-19 L. R. Yungelson

Prior to the explosive burning of a white dwarf (WD) that makes a Type Ia supernova (SN Ia), the star "simmers" for ~10^3 yrs in a convecting, carbon burning region. I estimate the excitation of g-modes by convection during this phase and…

High Energy Astrophysical Phenomena · Physics 2015-05-28 Anthony L. Piro

Recently a new class of hot subluminous stars strongly enriched in C and O have been discovered (CO-sdOs). These stars show abundances very similar to those observed in PG1159 stars but at lower temperatures. Moreover, it has been recently…

Solar and Stellar Astrophysics · Physics 2022-02-23 Marcelo M. Miller Bertolami , Tiara Battich , Alejandro H. Córsico , Leandro G. Althaus , Felipe C. Wachlin

(Abridged abstract) We explore the formation of ultra-massive (M_{\rm WD} \gtrsim 1.05 M_\sun$), carbon-oxygen core white dwarfs resulting from single stellar evolution. We also study their evolutionary and pulsational properties and…

We construct time-dependent one-dimensional (vertically averaged) models of accretion disks produced by the tidal disruption of a white dwarf (WD) by a binary neutron star (NS) companion. Nuclear reactions in the disk midplane burn the WD…

High Energy Astrophysical Phenomena · Physics 2016-09-16 Ben Margalit , Brian D. Metzger

We have explored in three dimensions the fate of a massive white dwarf as a function of different initial locations of carbon ignition, with the aid of a SPH code. The calculated models cover a variety of possibilities ranging from the…

Astrophysics · Physics 2015-06-24 Eduardo Bravo , Domingo Garcia-Senz

We have investigated the consequences of merging double white dwarf systems by calculating evolutionary models of accreting white dwarfs. We have considered two cases; a massive C-O white dwarf of ~1M_sun accreting C-O mixture, and a low…

Astrophysics · Physics 2009-10-30 H. Saio , K. Nomoto