Nucleosynthesis Calculations from Core-Collapse Supernovae
Christopher L. Fryer, Patrick Young, Michael Bennett, Steven Diehl, Falk Herwig, Raphael Hirschi, Aimee Hungerford, Marco Pignatari, Georgios Magkotsios, Gabrie… 展开作者
Christopher L. Fryer, Patrick Young, Michael Bennett, Steven Diehl, Falk Herwig, Raphael Hirschi, Aimee Hungerford, Marco Pignatari, Georgios Magkotsios, Gabriel Rockefeller, Francis X. Timmes
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To appear in the Conference Proceedings for the "10th Symposium on Nuclei in the Cosmos (NIC X)", July 27 - August 1 2008, Mackinack Island, Michigan, USA
We review some of the uncertainties in calculating nucleosynthetic yields, focusing on the explosion mechanism. Current yield calculations tend to either use a piston, energy injection, or enhancement of neutrino opacities to drive an explosion. We show that the energy injection, or more accurately, an entropy injection mechanism is best-suited to mimic our current understanding of the convection-enhanced supernova engine. The enhanced neutrino-opacity technique is in qualitative disagreement with simulations of core-collapse supernovae and will likely produce errors in the yields. But piston-driven explosions are the most discrepant. Piston-driven explosion severely underestimate the amount of fallback, leading to order-of-magnitude errors in the yields of heavy elements. To obtain yields accurate to the factor of a few level, we must use entropy or energy injection and this has become the NuGrid collaboration approach.
A simple description of core-collapse supernovae is given. Properties of the neutrino-driven wind, neutrino fluxes and luminosities, reaction rates, and the equilibrium electron fraction in supernova environments are discussed. Neutrino mixing and neutrino interactions that are relevant to core-collapse supernovae are briefly reviewed. The values of electron fraction under several evolution scenarios that may impact rapid neutron capture process (r-process) nucleosynthesis are calculated.
We present the basic properties of the yields of our latest set of presupernova evolution and explosive nucleosynthesis of massive stars in the range between 11 and 120 Msun having solar and zero metallicity.
We have studied detailed nucleosynthesis in the shocked surface layers of an Oxygen-Neon-Magnesium core collapse supernova with an eye to determining if the conditions are suitable for r process nucleosynthesis. We find no such conditions in an unmodified model, but do find overproduction of N=50 nuclei (previously seen in early neutron-rich neutrino winds) in amounts that, if ejected, would pose serious problems for galactic chemical evolution.
Presupernova evolution and explosive nucleosynthesis in massive stars for main-sequence masses from 13 $M_\odot$ to 70 $M_\odot$ are calculated. We examine the dependence of the supernova yields on the stellar mass, $^{12}C(α, γ) ^{16}O}$ rate, and explosion energy. The supernova yields integrated over the initial mass function are compared with the solar abundances.
Stars more massive than $\sim$ 20 - 25 \ms form a black hole at the end of their evolution. Stars with non-rotating black holes are likely to collapse "quietly" ejecting a small amount of heavy elements (Faint supernovae). In contrast, stars with rotating black holes are likely to give rise to very energetic supernovae (Hypernovae). We present distinct nucleosynthesis features of these two types of "black-hole-forming" supernovae. Nucleosynthesis in Hypernovae is characterized by larger abundance ratios (Zn,Co,V,Ti)/Fe and smaller (Mn,Cr)/Fe than normal supernovae, which can explain the observ…
We present a new set of presupernova evolutions and explosive yields of massive stars of initial solar composition (Y=0.285, Z=0.02) in the mass range 13-35 Msun. All the models have been computed with the latest version (4.97) of the FRANEC code that now includes a nuclear network extending from neutrons to Mo98. The explosive nucleosynthesis has been computed twice: a first one with an hydro code and a second one following the simpler radiation dominated shock approximation (RDA).
We study the few body reactions in explosive nucleosynthesis of light-to-heavy mass elements in various astrophysical conditions. In neutrino-driven winds of gravitational core collapse of SNeII, several light nuclei as well as heavy unstable nuclei paly significant roles in producing r-process elements. We discuss how the three-body reaction $^4$He$(αn, γ)^9$Be, whose cross section is poorly known, plays very critical role. We make note that several other reactions in the r-process are relevant to a Big-Bang nucleosynthesis. We discuss briefly a Galactic chemical evolution.
We present a new analysis of the abundances observed in extremely metal poor stars based on both a new generation of theoretical presupernova models and explosions of zero metallicity massive stars and a new abundance analysis of an homogeneous sample of stars having [Fe/H]<-2.5 (Cayrel et al. 2004).
Core collapse supernovae are the leading actor in the story of the cosmic origin of the chemical elements. Existing models, which generally assume spherical symmetry and parameterize the explosion, have been able to broadly replicate the observed elemental pattern. However, inclusion of neutrino interactions produces noticeable improvement in the composition of the ejecta when compared to observations. Neutrino interactions may also provide a supernova source for light p-process nuclei.
Motivated by observations of supernova SN 1987A, various authors have simulated Rayleigh-Taylor (RT) instabilities in the envelopes of core collapse supernovae (for a review, see Mueller 1998). The non-radial motion found in these simulations qualitatively agreed with observations in SN 1987A, but failed to explain the extent of mixing of newly synthesized 56Ni quantitatively. Here we present results of a 2D hydrodynamic simulation which re-addresses this failure and covers the entire evolution of the first 5 hours after core bounce.
We present our first nucleosynthesis results from a numerical simulation of the thermonuclear disruption of a static cold Chandrasekhar-mass C/O white dwarf. The two-dimensional simulation was performed with an adaptive-mesh Eulerian hydrodynamics code, FLASH, that uses as a flame capturing scheme the evolution of a passive scaler. To compute the isotopic yields and their velocity distribution, 10,000 massless tracer particles are embedded in the star. The particles are advected along streamlines and provide a Lagrangian description of the explosion. We briefly describe our verification tests …
There have been attempts to fit the abundance patterns of extremely metal-poor stars with supernova nucleosynthesis models for the lighter elements than Zn. On the other hand, observations have revealed that the presence of EMP stars with peculiarly high ratio of "weak r-process elements" Sr, Y and Zr. Although several possible processes were suggested for the origin of these elements, the complete solution for reproducing those ratios is not found yet. In order to reproduce the abundance patterns of such stars, we investigate a model with neutron rich matter ejection from the inner region of …
We study the r-process nucleosynthesis in neutrino-driven winds of gravitational core collapse SNeII. Appropriate physical conditions are found for successful r-process nucleosynthesis, which meet with several features of heavy elements discovered recently in metal-deficient halo stars. We find also several difficulties which are not explained in the present wind models. We discuss quests for new insights in nuclear physics, astrophysics, and astronomy.
We explore the effects on nucleosynthesis in Type II supernovae of various parameters (mass cut, neutron excess, explosion energy, progenitor mass) in order to explain the observed trends of the iron-peak element abundance ratios ([Cr/Fe], [Mn/Fe], [Co/Fe] and [Ni/Fe]) in halo stars as a function of metallicity for the range $ -4 \le$ [Fe/H] $\le -2.5$. [Cr/Fe] and [Mn/Fe] decrease with decreasing [Fe/H], while [Co/Fe] behaves the opposite way and increases. We show that such a behavior can be explained by a variation of mass cuts in Type II supernovae as a function of progenitor mass, which p…
Recent observation of the power spectrum of Cosmic Microwave Background (CMB) Radiation has exhibited that the flat cosmology is most likely. This suggests too large universal baryon-density parameter $Ω_b h^2 \approx 0.022 \sim 0.030$ to accept a theoretical prediction, $Ω_b h^2 \le 0.017$, in the homogeneous Big-Bang model for primordial nucleosynthesis. Theoretical upper limit arises from the sever constraints on the primordial $^7$Li abundance. We propose two cosmological models in order to resolve the descrepancy; lepton asymmetric Big-Bang nucleosynthesis model, and baryon inhomogeneous …
We examine nucleosynthesis in the electron capture supernovae of progenitor AGB stars with an O-Ne-Mg core (with the initial stellar mass of 8.8 M_\odot). Thermodynamic trajectories for the first 810 ms after core bounce are taken from a recent state-of-the-art hydrodynamic simulation. The presented nucleosynthesis results are characterized by a number of distinct features that are not shared with those of other supernovae from the collapse of stars with iron core (with initial stellar masses of more than 10 M_\odot). First is the small amount of 56Ni (= 0.002-0.004 M_\odot) in the ejecta, whi…
We investigate the effects of neutrino-nucleus interactions (the nu-process) on the production of iron-peak elements in Population III core-collapse supernovae. The nu-process and the following proton and neutron capture reactions produce odd-Z iron-peak elements in complete and incomplete Si burning region. This reaction sequence enhances the abundances of Sc, Mn, and Co in the supernova ejecta. The supernova explosion models of 15 M_sol and 25 M_sol stars with the nu-process well reproduce the averaged Mn/Fe ratio observed in extremely metal-poor halo stars. In order to reproduce the observe…
We review the nucleosynthesis yields of core-collapse supernovae (SNe) for various stellar masses, explosion energies, and metallicities. Comparison with the abundance patterns of metal-poor stars provides excellent opportunities to test the explosion models and their nucleosynthesis. We show that the abundance patterns of extremely metal-poor (EMP) stars, e.g., the excess of C, Co, Zn relative to Fe, are in better agreement with the yields of hyper-energetic explosions (Hypernovae, HNe) rather than normal supernovae. We note that the variation of the abundance patterns of EMP stars are relate…
It has been recently proposed that the shocked surface layers of exploding O-Ne-Mg cores provide the conditions for r-process nucleosynthesis, because their rapid expansion and high entropies enable heavy r-process isotopes to form even in an environment with very low initial neutron excess of the matter. We show here that the most sophisticated available hydrodynamic simulations (in spherical and axial symmetry) do not support this new r-process scenario because they fail to provide the necessary conditions of temperature, entropy, and expansion timescale by significant factors. This suggests…
The influence of the initial composition of the exploding white dwarf on the nucleosynthesis, light curves and spectra of Type Ia supernovae has been studied in order to evaluate the size of evolutionary effects on cosmological time scales, how the effects can be recognized and how one may be able to correct for them. The calculations are based on a set of delayed detonation models which give a good account of the optical and infrared light curves and of the spectral evolution. The explosions and light curves are calculated using a one- dimensional Lagrangian radiation-hydro code including a n…
Among the major uncertainties involved in the Chandrasekhar mass models for Type Ia supernovae are the companion star of the accreting white dwarf (or the accretion rate that determines the carbon ignition density) and the flame speed after ignition. We present nucleosynthesis results from relatively slow deflagration (1.5 - 3 % of the sound speed) to constrain the rate of accretion from the companion star. Because of electron capture, a significant amount of neutron-rich species such as ^{54}Cr, ^{50}Ti, ^{58}Fe, ^{62}Ni, etc. are synthesized in the central region. To avoid the too large rati…
The luminosity distance vs. redshift law is now measured using supernovae and gamma ray bursts, and the angular size distance is measured at the surface of last scattering by the CMB and at z = 0.35 by baryon acoustic oscillations. In this paper this data is fit to models for the equation of state with w = -1, w = const, and w(z) = w_0+w_a(1-a). The last model is poorly constrained by the distance data, leading to unphysical solutions where the dark energy dominates at early times unless the large scale structure and acoustic scale constraints are modified to allow for early time dark energy e…
We present new nucleosynthesis yields as functions of the stellar mass, metallicity, and explosion energy (corresponding to normal supernovae and Hypernovae). We apply the results to the chemical evolution of the solar neighborhood. Our new yields are based on the new developments in the observational/theoretical studies of supernovae (SNe) and extremely metal-poor (EMP) stars in the halo, which have provided excellent opportunities to test the explosion models and their nucleosynthesis. We use the light curve and spectra fitting of individual SN to estimate the mass of the progenitor, explosi…
The explosion of a white dwarf of mass 1.36 M$_\odot$ has been simulated in three dimensions with the aid of a SPH code. The explosion follows the delayed detonation paradigma. In this case the deflagration-detonation transition is induced by the large corrugation of the flame front resulting from Rayleigh-Taylor instability and turbulence. The nucleosynthetic yields have been calculated, showing that some neutronized isotopes such as 54^Fe or 58^Ni are not overproduced with respect to the solar system ratios. The distribution of intermediate-mass elements is also compatible with the spectra o…
We explore the sensitivity of the nucleosynthesis of intermediate mass elements (28 < A < 80) in supernovae derived from massive stars to the nuclear reaction rates employed in the model. Two standard sources of reaction rate data (Woosley et al. 1978; and Thielemann et al. 1987) are employed in pairs of calculations that are otherwise identical. Both include as a common backbone the experimental reactions rates of Caughlan & Fowler (1988). Two stellar models are calculated for each of two main sequence masses: 15 and 25 solar masses. Each star is evolved from core hydrogen burning to a presup…
This manuscript reviews recent progress in our understanding of the nucleosynthesis of medium and heavy elements in supernovae. Recent hydrodynamical models of core-collapse supernovae show that a large amount of proton rich matter is ejected under strong neutrino fluxes. This matter constitutes the site of the vp-process where antineutrino absorption reactions catalyze the nucleosynthesis of nuclei with A > 64. Supernovae are also associated with the r-process responsible for the synthesis of the heaviest elements in nature. Fission during the r-process can play a major role in determining th…
We investigate $r$-process nucleosynthesis during the magnetohydrodynamical (MHD) explosion of supernova in a massive star of 13 $M_{\odot}$. Contrary to the case of the spherical explosion, jet-like explosion due to the combined effects of the rotation and magnetic field lowers the electron fraction significantly inside the layers above the iron core. We find that the ejected material of low electron fraction responsible for the $r$-process comes out from the silicon rich layer of the presupernova model. This leads to the production up to the third peak in the solar $r$-process elements. We e…
Core collapse supernovae are dominated by energy transport from neutrinos. Therefore, some supernova properties could depend on symetries and features of the standard model weak interactions. The cross section for neutrino capture is larger than that for antineutrino capture by one term of order the neutrino energy over the nucleon mass. This reduces the ratio of neutrons to protons in the $ν$-driven wind above a protoneutron star by approximately 20 % and may significantly hinder r-process nucleosynthesis.
We calculate nucleosynthesis in core-collapse explosions of massive Pop III stars, and compare the results with abundances of metal-poor halo stars to constrain the parameters of Pop III supernovae. We focus on iron-peak elements and, in particular, we try to reproduce the large [Zn/Fe] observed in extremely metal-poor stars. The interesting trends of the observed ratios [Zn, Co, Mn, Cr, V/Fe] can be related to the variation of the relative mass of the complete and incomplete Si-burning regions in supernova ejecta. We find that [Zn/Fe] is larger for deeper mass-cuts, smaller neutron excess, an…
X-ray observations have shown that the chemical abundance in the starburst galaxy M82 is quite rich in Si and S compared with oxygen. Such an abundance pattern cannot be explained with any combination of conventional Type I and II supernova yields. Also the energy to heavy element mass ratio of the observed hot plasma is much higher than the value resulted from normal supernovae. We calculate explosive nucleosynthesis in core-collapse hypernovae and show that the abundance pattern and the large ratio between the energy and the heavy element mass can be explained with the hypernova nucleosynthe…
The collapsar engine behind long-duration gamma-ray bursts extracts the energy released from the rapid accretion of a collapsing star onto a stellar-massed black hole. In a collapsing star, this black hole can form in two ways: the direct collapse of the stellar core into a black hole and the delayed collapse of a black hole caused by fallback in a weak supernova explosion. In the case of a delayed-collapse black hole, the strong collapsar-driven explosion overtakes the weak supernova explosion before shock breakout, and it is very difficult to distinguish this black hole formation scenario fr…
We present details of our investigation of the progenitors to core-collapse supernovae. We discuss observations and the theory of the lowest-mass stars to explode as supernovae.
We review the characteristics of nucleosynthesis in 'Hypernovae', i.e., supernovae with very large explosion energies ($ \gsim 10^{52} $ ergs). The hypernova yields compared to those of ordinary core-collapse supernovae show the following characteristics: 1) Complete Si-burning takes place in more extended region, so that the mass ratio between the complete and incomplete Si burning regions is generally larger in hypernovae than normal supernovae. As a result, higher energy explosions tend to produce larger [(Zn, Co)/Fe], smaller [(Mn, Cr)/Fe], and larger [Fe/O], which could explain the trend …
We calculate evolution, collapse, explosion, and nucleosynthesis of Population III very-massive stars with 500$M_{\odot}$ and 1000$M_{\odot}$. Presupernova evolution is calculated in spherical symmetry. Collapse and explosion are calculated by a two-dimensional code, based on the bipolar jet models. We compare the results of nucleosynthesis with the abundance patterns of intracluster matter, hot gases in M82, and extremely metal-poor stars in the Galactic halo. It was found that both 500$M_{\odot}$ and 1000$M_{\odot}$ models enter the region of pair-instability but continue to undergo core col…
We study nucleosynthesis in 'hypernovae', i.e., supernovae with very large explosion energies ($ \gsim 10^{52} $ ergs) for both spherical and aspherical explosions. The hypernova yields compared to those of ordinary core-collapse supernovae show the following characteristics: 1) Complete Si-burning takes place in more extended region, so that the mass ratio between the complete and incomplete Si burning regions is generally larger in hypernovae than normal supernovae. As a result, higher energy explosions tend to produce larger [(Zn, Co)/Fe], small [(Mn, Cr)/Fe], and larger [Fe/O], which could…
During the last few years, a number of exceptional core-collapse supernovae (SNe) have been discovered. Their kinetic energy of the explosions are larger by more than an order of magnitude than the typical values for this type of SNe, so that these SNe have been called `Hypernovae'. We first describe how the basic properties of hypernovae can be derived from observations and modeling. These hypernovae seem to come from rather massive stars, thus forming black holes. On the other hand, there are some examples of massive SNe with only a small kinetic energy. We suggest that stars with non-rotati…
We calculate explosive nucleosynthesis in Chandrasekhar mass models for Type Ia Supernovae(SNe Ia) to obtain new constraints on the rate of matter accretion onto the progenitor white dwarf and on the ignition density of central carbon deflagration. The calculated abundance of the Fe-group neutron-rich nuclei is highly sensitive to the electron captures taking place in the central layers. The yields obtained from a slow central deflagration, and from a fast deflagration or delayed detonation in the outer layers, are combined and put to comparison with solar isotopic abundances. We found that (1…
To constrain the conditions for very early nucleosynthesis in the Universe we compare the chemical enrichment pattern of an extremely metal-poor damped Lyman alpha (DLA) absorber with predictions from recent explosive nucleosynthesis model calculations. For this, we have analyzed chemical abundances in the DLA system at z_abs=2.6183 toward the quasar Q0913+072 (z_em=2.785) using public UVES/VLT high spectral resolution data. The total neutral hydrogen column density in this absorber is logN(HI)=20.36. Accurate column densities are derived for CII, NI, OI, AlII, SiII, and FeII. Upper limits are…
We calculate nucleosynthesis in Population (Pop) III supernovae (SNe) and compare the yields with various abundance patterns of extremely metal-poor (EMP) stars. We assume that the observed EMP stars are the second generation stars, which have the metal-abundance patterns of Pop III SNe. Previous theoretical yields of Pop III SNe cannot explain the trends in the abundance ratios among iron-peak elements (Mn, Co, Ni, Zn)/Fe as well as the large C/Fe ratio observed in certain EMP stars with [Fe/H] <~ -2.5. In the present paper, we show that if we introduce higher explosion energies and mixing-fa…
We examine the characteristics of nucleosynthesis in 'hypernovae', i.e., supernovae with very large explosion energies ($ \gsim 10^{52} $ ergs). We carry out detailed nucleosynthesis calculations for these energetic explosions and compare the yields with those of ordinary core-collapse supernovae. We find that both complete and incomplete Si-burning takes place over more extended, lower density regions, so that the alpha-rich freezeout is enhanced and produces more Ti in comparison with ordinary supernova nucleosynthesis. In addition, oxygen and carbon burning takes place in more extended, low…
Explosive nucleosynthesis under the axisymmetric explosion in Type II supernova has been performed by means of two dimensional hydrodynamical calculations. We have compared the results with the observations of SN 1987A. Our chief findings are as follows: (1) $^{44}Ti$ is synthesized so much as to explain the tail of the bolometric light curve of SN 1987A. We think this is because the alpha-rich freezeout takes place more actively under the axisymmetric explosion. (2) $^{57}Ni$ and $^{58}Ni$ tend to be overproduced compared with the observations. However, this tendency relies strongly on the pr…
The most energetic part of the electromagnetic spectrum bears the purest clues to the synthesis of atomic nuclei in the universe. The decay of radioactive species, synthesized in stellar environments and ejected into the interstellar medium, gives rise to specific gamma ray lines. The observations gathered up to now show evidence for radioactivities throughout the galactic disk, in young supernova remnants (Cas A, Vela), and in nearby extragalactic supernovae (SN 1987A, SN 1991T and SN1998bu), in the form of specific gamma ray lines resulting, respectively, from the radioactive decay of 26Al, …
We examine the characteristics of nucleosynthesis in 'hypernovae', i.e., supernovae with very large explosion energies ($\gsim 10^{52}$ ergs). Implications for the cosmic chemical evolution and the abundances in M82 are discussed.
This review concentrates on nucleosynthesis processes in general and their applications to massive stars and supernovae. A brief initial introduction is given to the physics in astrophysical plasmas which governs composition changes. We present the basic equations for thermonuclear reaction rates and nuclear reaction networks. The required nuclear physics input for reaction rates is discussed, i.e. cross sections for nuclear reactions, photodisintegrations, electron and positron captures, neutrino captures, inelastic neutrino scattering, and beta-decay half-lives. We examine especially the pre…
We report a current status of our radiation-magnetohydrodynamic code for the study of core-collapse supernovae. In this contribution, we discuss the accuracy of our newly developed numerical code by presenting the test problem in a static background model. We also present the application to the spherically symmetric core-collapse simulations. Since close comparison with the previously published models is made, we are now applying it for the study of magnetorotational core-collapse supernovae.
Identifying the massive progenitor stars that give rise to core-collapse supernovae is one of the main pursuits of supernova and stellar evolution studies. In this talk I discuss some aspects of the pursuit of these progenitor stars in ground-based and Hubble Space Telescope images.
Recent progress in modeling core-collapse supernovae is summarized and set in perspective. Two-dimensional simulations with state-of-the-art treatment of neutrino transport still fail to produce powerful explosions, but evidence is presented that they are very close to success.
Core-collapse supernovae are dramatic events with a rich phenomenology, including gravitational radiation. Simulations of these events in multiple spatial dimensions with energy- and angle-dependent neutrino transport are still in their infancy. Core collapse and bounce in a supernova in our galaxy may well be visible by first-generation LIGO, but detailed understanding waits on improvements in modeling both stellar progenitors and the supernova process.
Recent nucleosynthesis calculations of Type II supernovae using advanced neutrino transport determine that the early neutrino winds are proton-rich. However, a fraction of the ejecta emitted at the same time is composed of neutron-rich pockets. In this paper we calculate the nucleosynthesis contribution from the neutron-rich pockets in the hot convective bubbles of a core-collapse supernova and show that they do not contribute significantly to the total nucleosynthesis.
We review the characteristics of nucleosynthesis in 'Hypernovae', i.e., core-collapse supernovae with very large explosion energies ($ \gsim 10^{52} $ ergs). The hypernova yields show the following characteristics: 1) The mass ratio between the complete and incomplete Si burning regions is larger in hypernovae than normal supernovae. As a result, higher energy explosions tend to produce larger [(Zn, Co, V)/Fe] and smaller [(Mn, Cr)/Fe], which could explain the trend observed in very metal-poor stars. 2) Because of enhanced $α$-rich freezeout, $^{44}$Ca, $^{48}$Ti, and $^{64}$Zn are produced mo…
In this paper, we discuss the current status of core collapse supernova models and the future developments needed to achieve significant advances in understanding the supernova mechanism and supernova phenomenology, i.e., in developing a supernova standard model.
The most important weak nuclear interaction to the dynamics of stellar core collapse is electron capture, primarily on nuclei with masses larger than 60. In prior simulations of core collapse, electron capture on these nuclei has been treated in a highly parameterized fashion, if not ignored. With realistic treatment of electron capture on heavy nuclei come significant changes in the hydrodynamics of core collapse and bounce. We discuss these as well as the ramifications for the post-bounce evolution in core collapse supernovae.
Jet-induced supernovae (SNe) have been suggested to occur in gamma-ray bursts (GRBs) and highly-energetic SNe (hypernovae). I investigate hydrodynamical and nucleosynthetic properties of the jet-induced explosion of a population III $40_\odot$ star with a two-dimensional special relativistic hydrodynamical code. The abundance distribution after the explosion and the angular dependence of the yield are obtained for the models with high and low energy deposition rates $\dot{E}_{\rm dep}=120\times10^{51} {\rm ergs s^{-1}}$ and $1.5\times10^{51} {\rm ergs s^{-1}}$. The ejection of Fe-peak products…
Recent observations have revealed many new puzzles related to core-collapse supernovae, including the formation of magnetars and black holes and their possible GRB connections. We review our current understanding of the origin of pulsar kicks and supernova asymmetry. It is argued that neutron star kicks are intimately connected to the other fundamental parameters of young neutron stars, such as the initial spin and magnetic field strength.
High-resolution two-dimensional simulations were performed for the first five minutes of the evolution of a core collapse supernova explosion in a 15 solar mass blue supergiant progenitor. The computations start shortly after bounce and include neutrino-matter interactions by using a light-bulb approximation for the neutrinos, and a treatment of the nucleosynthesis due to explosive silicon and oxygen burning. We find that newly formed iron-group elements are distributed throughout the inner half of the helium core by Rayleigh-Taylor instabilities at the Ni+Si/O and C+O/He interfaces, seeded by…
We explore the effect of the neutrino magnetic moment on neutrino scattering with matter in a core-collapse Supernova. We study the impact both on the neutrino fluxes and on the electron fraction. We find that sizeable modifications require very large magnetic moments both for Dirac and Majorana neutrinos.
Hans Bethe contributed in many ways to our understanding of the supernovae that happen in massive stars, but, to this day, a first principles model of how the explosion is energized is lacking. Nevertheless, a quantitative theory of nucleosynthesis is possible. We present a survey of the nucleosynthesis that occurs in 32 stars of solar metallicity in the mass range 12 to 120 solar masses. The most recent set of solar abundances, opacities, mass loss rates, and current estimates of nuclear reaction rates are employed. Restrictions on the mass cut and explosion energy of the supernovae based upo…
This overview discusses issues relevant to modeling nucleosynthesis in type II supernovae and implications of detailed studies of the ejecta. After a brief presentation of the most common approaches to stellar evolution and parameterized explosions, the relevance of a number of nuclei to obtain information on the evolution and explosion mechanisms is discussed. The paper is concluded by an outlook on multi-dimensional simulations.
We show that the observed ratio of the subtypes Ib,c and II core-collapse supernovae depends on the metallicity of the host galaxy, as expected on theoretical grounds. However, the observed relation differs considerably from expectations based on non-rotating models of single stars with mass loss. We argue that the predictions of recent models with rotation offer a much better agreement with observations, at least for progenitor stars with solar metallicity; calculations of models with higher and lower metallicities are required in order to substantiate these conclusions. We also suggest that …
