199 research outputs found
Explosive Nucleosynthesis in Near-Chandrasekhar Mass White Dwarf Models for Type Ia Supernovae: Dependence on Model Parameters
We present two-dimensional hydrodynamics simulations of near-Chandrasekhar
mass white dwarf (WD) models for Type Ia supernovae (SNe Ia) using the
turbulent deflagration model with deflagration-detonation transition (DDT). We
perform a parameter survey for 41 models to study the effects of the initial
central density (i.e., WD mass), metallicity, flame shape, DDT criteria, and
turbulent flame formula for a much wider parameter space than earlier studies.
The final isotopic abundances of C to Tc in these simulations are
obtained by post-process nucleosynthesis calculations. The survey includes SNe
Ia models with the central density from g cm to g cm (WD masses of 1.30 - 1.38 ), metallicity from
0 to 5 , C/O mass ratio from 0.3 - 1.0 and ignition kernels
including centered and off-centered ignition kernels. We present the yield
tables of stable isotopes from C to Zn as well as the major
radioactive isotopes for 33 models. Observational abundances of Mn,
Fe, Fe and Ni obtained from the solar composition,
well-observed SNe Ia and SN Ia remnants are used to constrain the explosion
models and the supernova progenitor. The connection between the pure turbulent
deflagration model and the subluminous SNe Iax is discussed. We find that
dependencies of the nucleosynthesis yields on the metallicity and the central
density (WD mass) are large. To fit these observational abundances and also for
the application of galactic chemical evolution modeling, these dependencies on
the metallicity and WD mass should be taken into account.Comment: 53 pages, 43 figures. Accepted for publication in Astrophysical
Journal. Tables and figures updated to be consistent with other works. Also
table magnified for better visio
Evolution and Nucleosynthesis of Metal-Free Massive Stars
We calculate presupernova evolutions and supernova explosions of massive
stars (M=13-25 Mo) for various metallicities. We find the following
characteristic abundance patterns of nucleosynthesis in the metal-free (Pop
III) stars. (1) The alpha-nuclei (from C to Zn) are more efficiently produced
than other isotopes, and the abundance pattern of alpha-nuclei can be similar
to the solar abundance. In particular, near solar ratios of alpha elements/Fe
might be a signature of Pop III which could produce a large amount of Fe. (2)
The abundance ratios of odd Z to even Z elements such as Na/Mg and Al/Mg become
smaller for lower metallicity. However, these ratios almost saturate below Z <~
10^{-5}, and [Na, Al/Mg] ~ - 1 for Pop III and low metal Pop II
nucleosynthesis. This result is consistent with abundance pattern of metal poor
stars, in which these ratios also saturate around -1. We suggest that these
stars with the lowest [Na/Mg] or [Al/Mg] may contain the abundance pattern of
Pop III nucleosynthesis. (3) Metal poor stars show interesting trends in the
ratios of [Cr, Mn, Co/Fe]. We discuss that these trends are not explained by
the differences in metallicity, but by the relative thickness between the
complete and the incomplete Si burning layers. Large [Co/Fe] and small [Cr,
Mn/Fe] values found in the observations are explained if mass cut is deep or if
matter is ejected from complete Si burning layer in a form of a jet or bullets.
(4) We also find that primary ^{14}N production occurs in the massive Pop III
stars, because these stars have radiative H-rich envelopes so that the
convective layer in the He-shell burning region can reach the H-rich region.Comment: 19 pages. To appear in the proceedings of the MPA/ESO conference
``The First Stars'' (August 4-7, 1999, Garching) ed. A. Weiss etal.
(Springer
Young and Massive Binary Progenitors of Type Ia Supernovae and Their Circumstellar Matter
We present new evolutionary models for Type Ia supernova (SN Ia) progenitors,
introducing mass-stripping effect on a main-sequence (MS) or slightly evolved
companion star by winds from a mass-accreting white dwarf (WD). The
mass-stripping attenuates the rate of mass transfer from the companion to the
WD. As a result, quite a massive MS companion can avoid forming a common
envelope and increase the WD mass up to the SN Ia explosion. Including the
mass-stripping effect, we follow binary evolutions of various WD + MS systems
and obtain the parameter region in the initial donor mass - orbital period
plane where SNe Ia occur. The newly obtained SN Ia region extends to donor
masses of 6-7 M_\sun, although its extension depends on the efficiency of
mass-stripping effect. The stripped matter would mainly be distributed on the
orbital plane and form very massive circumstellar matter (CSM) around the SN Ia
progenitor. It can explain massive CSM around SNe Ia/IIn(IIa) 2002ic and 2005gj
as well as tenuous CSM around normal SN Ia 2006X. Our new model suggests the
presence of very young (\lesssim 10^8 yr) populations of SNe Ia, being
consistent with recent observational indications of young population SNe Ia.Comment: 15 pages including 12 figures, to appear in ApJ, minor corrections to
ver.
Pulsational Pair-instability Supernovae. I. Pre-collapse Evolution and Pulsational Mass Ejection
We calculate the evolution of massive stars, which undergo pulsational
pair-instability (PPI) when the O-rich core is formed. The evolution from the
main-sequence through the onset of PPI is calculated for stars with the initial
masses of and metallicities of
. Because of mass loss, is necessary for stars
to form He cores massive enough (i.e., mass ) to undergo PPI. The
hydrodynamical phase of evolution from PPI through the beginning of Fe core
collapse is calculated for the He cores with masses of and
. During PPI, electron-positron pair production causes a rapid
contraction of the O-rich core which triggers explosive O-burning and a
pulsation of the core. We study the mass dependence of the pulsation dynamics,
thermodynamics, and nucleosynthesis. The pulsations are stronger for more
massive He cores and result in such a large amount of mass ejection such as for He cores. These He cores eventually
undergo Fe-core collapse. The He core undergoes complete
disruption and becomes a pair-instability supernova. The H-free circumstellar
matter ejected around these He cores is massive enough for to explain the
observed light curve of Type I (H-free) superluminous supernovae with
circumstellar interaction. We also note that the mass ejection sets the maximum
mass of black holes (BHs) to be , which is consistent with
the masses of BHs recently detected by VIRGO and aLIGO.Comment: 33 pages, 57 figures, submitted at 29 January 2019, revised at 16
October 2019, accepted at 20 October 2019; published 11 December 2019.
References and metadata update
Yields of Population III Supernovae and the Abundance Patterns of Extremely Metal-Poor Stars
The abundance patterns of extremely metal-poor (EMP) stars provide us with
important information on nucleosynthesis in supernovae (SNe) formed in a Pop
III or EMP environment, and thus on the nature of the first stars in the
Universe. We review nucleosynthesis yields of various types of those SNe,
focusing on core-collapse (black-hole-forming) SNe with various progenitor
masses, explosion energies (including Hypernovae), and asphericity. We discuss
the implications of the observed trends in the abundance ratios among iron-peak
elements, and the large C/Fe ratio observed in certain EMP stars with
particular attention to recently discovered hyper metal-poor (HMP) stars. We
show that the abundance pattern of the HMP stars with [Fe/H] < -5 and other EMP
stars are in good accord with those of black-hole-forming supernovae, but not
pair-instability supernovae. This suggests that black-hole-forming supernovae
made important contributions to the early Galactic (and cosmic) chemical
evolution. Finally we discuss the nature of First (Pop III) Stars.Comment: Published in "IAU Symp. 228: From Lithium to Uranium: Elemental
Tracers of Early Cosmic Evolution", ed. V. Hill, P. Francois, and F. Primas
(Cambridge University Press) 287-296 (2005
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