scholarly journals White Dwarf Models for Type I Supernovae and Quiet Supernovae, and Presupernova Evolution

1980 ◽  
Vol 58 ◽  
pp. 563-570
Author(s):  
Ken’ichi Nomoto
Keyword(s):  
Neutron Stars ◽  
White Dwarf ◽  
White Dwarfs ◽  
Accretion Rate ◽  
Initial Mass ◽  
Type I ◽  
Plausible Mechanism

AbstractSupernova mechanisms in accreting white dwarfs (WDs) are presented, i.e., the carbon deflagration as a plausible mechanism for producing Type I supernovae and electron captures to form quiet supernovae leaving neutron stars. These outcomes depend on accretion rate of helium, initial mass and composition of the WD. The various types of hydrogen shell-burning in the présupernova stage are also discussed.

scholarly journals Supernova Explosions in Degenerate Stars —Detonation, Deflagration, and Electron Capture—

1981 ◽  
Vol 93 ◽  
pp. 295-315
Author(s):  
Ken'ichi Nomoto
Keyword(s):  
Neutron Stars ◽  
Electron Capture ◽  
White Dwarf ◽  
White Dwarfs ◽  
Accretion Rate ◽  
The Other ◽  
Type I ◽  
Hydrodynamic Behavior ◽  
Other Hand ◽  
Supernova Explosions

Presupernova evolution and the hydrodynamic behavior of supernova explosions in stars having electron-degenerate cores are summarized. Carbon deflagration supernovae in C+O cores disrupt the star completely. On the other hand, in electron capture supernovae, O+Ne+Mg cores collapse to form neutron stars despite the competing oxygen deflagration.Also discussed are white dwarf models for Type I supernovae (SN I). Supernova explosions in accreting white dwarfs are either the detonation or deflagration type depending mainly on the accretion rate. The carbon deflagration model reproduces many of the observed features of SN I.

scholarly journals Are the Precursors of Type Ia Supernovae Double Degenerate Mergers?

2004 ◽  
Vol 194 ◽  
pp. 111-112
Author(s):  
Lilia Ferrario
Keyword(s):  
Neutron Stars ◽  
White Dwarf ◽  
White Dwarfs ◽  
Observational Evidence ◽  
Type Ia Supernovae ◽  
Type Ia ◽  
Ia Supernovae

AbstractI argue that the observational evidence for white dwarf-white dwarf mergers supports the view that they give rise to ultra-massive white dwarfs or neutron stars through accretion induced collapse. The implications for the progenitors of Type Ia SNe are discussed.

scholarly journals Growth Rate of White Dwarf Mass in Binaries

1989 ◽  
Vol 114 ◽  
pp. 507-510
Author(s):  
Mariko Kato ◽  
Hideyuki Saio ◽  
Izumi Hachisu
Keyword(s):  
Growth Rate ◽  
Steady State ◽  
Star Formation ◽  
Neutron Star ◽  
Mass Loss ◽  
White Dwarf ◽  
Accretion Rate ◽  
Time Dependent ◽  
Type I ◽  
Wide Range

AbstractThe growth rate of a white dwarf which accretes hydrogen-rich or helium matter is studied. If the accretion rate is relatively small, unstable shell flash occurs and during which the envelope mass is lost. We have followed the evolutions of shell flashes by steady state approach with wind mass loss solutions to determined the mass lost from the system for wide range of binary parameters. The time-dependent models are also calculated in some cases. The mass loss due to the Roche lobe overflow are taken into account. This results seriously affects the existing scenarios on the origin of the type I supernova or on the neutron star formation induced by accretion.

scholarly journals Evidence of spectral evolution on the white dwarf sample from the Gaia mission

2020 ◽  
Vol 492 (4) ◽  
pp. 5003-5010 ◽  
Author(s):  
G Ourique ◽  
S O Kepler ◽  
A D Romero ◽  
T S Klippel ◽  
D Koester
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
Mass Function ◽  
Initial Mass Function ◽  
Star Formation History ◽  
Initial Mass ◽  
Spectral Evolution ◽  
Formation History ◽  
Magnitude Diagram ◽  
Double Population

ABSTRACT Since the Gaia data release 2, several works have been published describing a bifurcation in the observed white dwarf colour−magnitude diagram for ${G_{\mathrm{BP}}}{}-{G_{\mathrm{RP}}}{} \gt 0$. Some possible explanations in the literature include the existence of a double population with different initial mass functions or two distinct populations, one formed by hydrogen-envelope and one formed by helium-envelope white dwarfs. We propose instead spectral evolution to explain the bifurcation. From a population synthesis approach, we find that spectral evolution occurs for effective temperatures below ${\simeq }11\, 000\, \mathrm{K}$ and masses mainly between $0.64\, \mathrm{M}_\odot$ and $0.74\, \mathrm{M}_\odot$, which correspond to around 16 per cent of all DA white dwarfs. We also find that the Gaia white dwarf colour–magnitude diagram indicates a star formation history that decreases abruptly for objects younger than $1.4\, \mathrm{Gyr}$ and a top-heavy initial mass function for the white dwarf progenitors.

scholarly journals Nova Explosion of Mass Accreting White Dwarfs

1979 ◽  
Vol 53 ◽  
pp. 529-529 ◽  
Author(s):  
Ken’ichi Nomoto ◽  
Kyoji Nariai ◽  
Daiichiro Sugimoto
Keyword(s):  
Temperature Distribution ◽  
White Dwarf ◽  
White Dwarfs ◽  
Accretion Rate ◽  
Thermal Structure ◽  
Stellar Surface

Evolution of a mass accreting white dwarf has been computed from the onset of accretion through nova explosion. We have considered a white dwarf of 1.3M⊙ with the accretion rate of 1×10-10M⊙ yr-1. Because the thermal structure during the accretion phase has been fully taken into computation, the mass of the accreted hydrogen-rich envelope and the corresponding temperature distribution in the envelope have been determined. When the hydrogen-rich envelope of mass ΔMH = 1.63 × 10-4M⊙ has been formed, a hydrogen-shell flashes commences. The flashing shell lies midway between the bottom of the envelope and the stellar surface; the mass lying above this shell is 5.7 × 10-5M⊙

scholarly journals On isolated millisecond pulsars formed by the coalescence of neutron stars and massive white dwarfs

2019 ◽  
Vol 36 ◽  
Author(s):  
Shengnan Sun ◽  
Lin Li ◽  
Helei Liu ◽  
Guoliang Lü ◽  
Zhaojun Wang ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Neutron Star ◽  
Neutron Stars ◽  
White Dwarf ◽  
White Dwarfs ◽  
Birth Rate ◽  
Population Synthesis ◽  
Solar Mass ◽  
Millisecond Pulsars ◽  
The Stability

Abstract This paper uses population synthesis to investigate the possible origin of isolated millisecond pulsars as born from the coalescence of a neutron star and a white dwarf. Results show that the galactic birth rate of isolated millisecond pulsars is likely to lie between 5.8×10−5 yr−1 and 2.0×10−4 yr−1, depending on critical variables, such as the stability of mass transfer via the Roche lobe and the value of kick velocity. In addition to this, this paper estimates that the solar mass of isolated millisecond pulsars can range from 1.5 and 2.0 Mʘ, making them more massive than other ‘normal’ pulsars. Finally, the majority of isolated millisecond pulsars in our simulations have spin periods ranging from several to 20 ms, which is consistent with previous observations.

scholarly journals The Coalescence of White Dwarfs And Type I Supernovae

1989 ◽  
Vol 114 ◽  
pp. 515-518
Author(s):  
Robert Mochkovitch ◽  
Mario Livio
Keyword(s):  
Angular Momentum ◽  
White Dwarf ◽  
Total Mass ◽  
White Dwarfs ◽  
Thick Disk ◽  
Initial System ◽  
Type I ◽  
Low Density ◽  
Coalescence Model ◽  
Merging Process

AbstractIn the context of the white dwarf coalescence model for type la supernovae, we compute post-coalescence configurations involving a thick disk, rotating around a central white dwarf (the original primary), having the same total mass, angular momentum and energy as the initial system. We show that carbon ignition in rather low density material (105 – 10° g.cm−3) can be triggered during the merging process itself or later, by dissipation due to turbulence in the disk. The evolution of the object following carbon ignition is very uncertain.

scholarly journals Magnetic White Dwarfs with Strong Fields and the Origin of Magnetism in White Dwarfs and Neutron Stars

1979 ◽  
Vol 53 ◽  
pp. 313-316 ◽  
Author(s):  
J. R. P. Angel
Keyword(s):  
Neutron Star ◽  
Magnetic Fields ◽  
Neutron Stars ◽  
White Dwarf ◽  
White Dwarfs ◽  
Strong Fields ◽  
Work In Progress ◽  
Field Strengths

Work in progress at Steward Observatory covering three aspects of magnetism in degenerate dwarfs is reviewed. First, the identification of the Minkowski bands in Grw + 70° 8247 with Zeeman transitions in hydrogen. Second, a determination of field strengths in the more strongly magnetic white dwarfs. Third, some observations and speculations concerning the origin of white dwarf and neutron star magnetic fields.

scholarly journals White Dwarf Models of Supernovae and Cataclysmic Variables

1987 ◽  
Vol 93 ◽  
pp. 395-411
Author(s):  
K. Nomoto ◽  
M. Hashimoto
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
Cataclysmic Variables ◽  
Reaction Rates ◽  
Type I ◽  
X Ray ◽  
Composition Structure ◽  
Helium Star ◽  
X Ray Binaries ◽  
Good Agreement

AbstractIf the accreting white dwarf increases its mass to the Chandrasekhar mass, it will either explode as a Type I supernova or collapse to form a neutron star. In fact, there is a good agreement between the exploding white dwarf model for Type I supernovae and observations. We describe various types of evolution of accreting white dwarfs as a function of binary parameters (i.e, composition, mass, and age of the white dwarf, its companion star, and mass accretion rate), and discuss the conditions for the precursors of exploding or collapsing white dwarfs, and their relevance to cataclysmic variables. Particular attention is given to helium star cataclysmics which might be the precursors of some Type I supernovae or ultrashort period X-ray binaries. Finally we present new evolutionary calculations using the updated nuclear reaction rates for the formation of O+Ne+Mg white dwarfs, and discuss the composition structure and their relevance to the model for neon novae.

scholarly journals Photometric Properties of White Dwarf Dominated Halos

2004 ◽  
Vol 21 (2) ◽  
pp. 153-156 ◽  
Author(s):  
Hyun-chul Lee ◽  
Brad K. Gibson ◽  
Yeshe Fenner ◽  
Chris B. Brook ◽  
Daisuke Kawata ◽  
...  
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
High Redshift ◽  
Mass Function ◽  
Large Magellanic Cloud ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Galactic Halos ◽  
Dark Halo ◽  
Dynamical Mass

AbstractUsing stellar population synthesis techniques, we explore the photometric signatures of white dwarf progenitor dominated galactic halos, in order to constrain the fraction of halo mass that may be locked up in white dwarf stellar remnants. We first construct a 109 M⊙ stellar halo using the canonical Salpeter initial stellar mass distribution, and then allow for an additional component of low- and intermediate-mass stars, which ultimately give rise to white dwarf remnants. Microlensing observations towards the Large Magellanic Cloud, coupled with several ground-based proper motion surveys, have led to claims that in excess of 20% of the dynamical mass of the halo (1012 M⊙) might be found in white dwarfs. Our results indicate that (1) even if only 1% of the dynamical mass of the dark halo today could be attributed to white dwarfs, their main sequence progenitors at high redshift (z ≈ 3) would have resulted in halos more than 100 times more luminous than those expected from conventional initial mass functions alone, and (2) any putative halo white dwarf progenitor dominated initial mass function component, regardless of its dynamical importance, would be virtually impossible to detect at the present day, due to its extremely faint surface brightness.

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