Composition of the Innermost Core‐Collapse Supernova Ejecta (original) (raw)
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The influence of the explosion Mechanism on the Fe-group ejecta of core collapse supernovae
Proceedings of the International Astronomical Union, 2005
Core collapse supernovae are responsible for at least half of the galactic inventory of Fe-group elements and probably for most of the Fe-group abundances seen in metal poor stars. Recent simulations show the emergence of a proton-rich (Y e > 0.5) region in the innermost ejected mass zones due to the neutrino interaction with matter. We explore the nucleosynthesis implications of these findings that result in enhanced abundances of 45 Sc, 49 Ti, and 64 Zn, which is consistent with chemical evolution studies and observations of low metallicity stars.
The Astrophysical Journal, 2011
We investigate explosive nucleosynthesis in a non-rotating 15M ⊙ star with solar metallicity that explodes by a neutrino-heating supernova (SN) mechanism aided by both standing accretion shock instability (SASI) and convection. To trigger explosions in our two-dimensional hydrodynamic simulations, we approximate the neutrino transport with a simple light-bulb scheme and systematically change the neutrino fluxes emitted from the protoneutron star. By a post-processing calculation, we evaluate abundances and masses of the SN ejecta for nuclei with the mass number ≤ 70 employing a large nuclear reaction network. Aspherical abundance distributions, which are observed in nearby core-collapse SN remnants, are obtained for the non-rotating spherically-symmetric progenitor, due to the growth of low-mode SASI. Abundance pattern of the supernova ejecta is similar to that of the solar system for models whose masses ranges (0.4 − 0.5)M ⊙ of the ejecta from the inner region (≤ 10, 000 km) of the precollapse core. For the models, the explosion energies and the 56 Ni masses are ≃ 10 51 erg and (0.05 − 0.06)M ⊙ , respectively; their estimated baryonic masses of the neutron star are comparable to the ones observed in neutron-star binaries. These findings may have little uncertainty because most of the ejecta is composed by matter that is heated via the shock wave and has relatively definite abundances. The abundance ratios for Ne, Mg, Si and Fe observed in Cygnus loop are well reproduced with the SN ejecta from an inner region of the 15M ⊙ progenitor.
Nucleosynthesis and Clump Formation in a Core-Collapse Supernova
The Astrophysical journal, 2000
High-resolution two-dimensional simulations were performed for the first 5 minutes of the evolution of a core-collapse supernova explosion in a 15 M middle dot in circle blue supergiant progenitor. The computations start shortly after bounce and include neutrino-matter interactions by using a lightbulb 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 convective overturn during the early stages of the explosion. Fast-moving nickel mushrooms with velocities up to approximately 4000 km s-1 are observed. This offers a natural explanation for the mixing required in light-curve and spectral synthesis studies of Type Ib explosions. A continuation of the calculations to later times, however, indicates that the iron velocities observ...
Neutrino mixing and nucleosynthesis in core-collapse supernovae
New Journal of Physics, 2005
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.
Comprehensive Analyses of the Neutrino-Process in the Core-collapsing Supernova
arXiv (Cornell University), 2022
We investigate the neutrino flavor change effects due to neutrino self-interaction, shock wave propagation as well as matter effect on the neutrino-process of the core-collapsing supernova (CCSN). For the hydrodynamics, we use two models: a simple thermal bomb model and a specified hydrodynamic model for SN1987A. As a pre-supernova model, we take an updated model adjusted to explain the SN1987A employing recent development of the (n, γ) reaction rates for nuclei near the stability line (A ∼ 100). As for the neutrino luminosity, we adopt two different models: equivalent neutrino luminosity and non-equivalent luminosity models. The latter is taken from the synthetic analyses of the CCSN simulation data which involved quantitatively the results obtained by various neutrino transport models. Relevant neutrino-induced reaction rates are calculated by a shell model for light nuclei and a quasiparticle random phase approximation model for heavy nuclei. For each model, we present abundances of the light nuclei (7 Li, 7 Be, 11 B and 11 C) and heavy nuclei (92 Nb, 98 Tc, 138 La and 180 Ta) produced by the neutrino-process. The light nuclei abundances turn out to be sensitive to the Mikheyev-Smirnov-Wolfenstein (MSW) region around ONe -Mg region while the heavy nuclei are mainly produced prior to the MSW region. Through the detailed analyses, we find that neutrino self-interaction becomes a key ingredient in addition to the MSW effect for understanding the neutrino-process and the relevant nuclear abundances. The normal mass hierarchy is shown to be more compatible with the meteorite data. Main nuclear reactions for each nucleus are also investigated in detail.
Open Questions in Stellar Nuclear Physics: I
AIP Conference Proceedings, 2004
No doubt, among the most exciting discoveries of the third millennium thus far are Oscillations of Massive Neutrinos and Dark Energy that leads to an accelerated expansion of the Universe. Accordingly, Nuclear Physics is presented with two extraordinary challenges: the need for precise (5% or better) prediction of solar neutrino fluxes within the Standard Solar Model, and the need for an accurate (5% or better) understanding of stellar evolution and in particular of Type Ia super nova that are used as cosmological standard candle. In contrast, much confusion is found in the field with contradicting data and strong statements of accuracy that can not be supported by current data. We discuss an experimental program to address these challenges and disagreements.
Integrated Nucleosynthesis in Neutrino-Driven Winds
The Astrophysical Journal, 2010
Although they are but a small fraction of the mass ejected in core-collapse supernovae, neutrinodriven winds (NDWs) from nascent proto-neutron stars (PNSs) have the potential to contribute significantly to supernova nucleosynthesis. In previous works, the NDW has been implicated as a possible source of r-process and light p-process isotopes. In this paper we present time-dependent hydrodynamic calculations of nucleosynthesis in the NDW which include accurate weak interaction physics coupled to a full nuclear reaction network. Using two published models of PNS neutrino luminosities, we predict the contribution of the NDW to the integrated nucleosynthetic yield of the entire supernova. For the neutrino luminosity histories considered, no true r-process occurs in the most basic scenario. The wind driven from an older 1.4M ⊙ model for a PNS is moderately neutronrich at late times however, and produces 87 Rb, 88 Sr, 89 Y, and 90 Zr in near solar proportions relative to oxygen. The wind from a more recently studied 1.27M ⊙ PNS is proton-rich throughout its entire evolution and does not contribute significantly to the abundance of any element. It thus seems very unlikely that the simplest model of the NDW can produce the r-process. At most, it contributes to the production of the N = 50 closed shell elements and some light p-nuclei. In doing so, it may have left a distinctive signature on the abundances in metal poor stars, but the results are sensitive to both uncertain models for the explosion and the masses of the neutron stars involved.
Detection of supernovae neutrinos with neutrino-iron scattering
Physical Review C, 2008
The νe− 56 Fe cross section is evaluated in the projected quasiparticle random phase approximation (PQRPA). This model solves the puzzle observed in RPA for nuclei with mass around 12 C, because it is the only RPA model that treats the Pauli principle correctly. The cross sections as a function of the incident neutrino energy are compared with recent theoretical calculations of similar models. The average cross section weighted with the flux spectrum yields a good agreement with the experimental data. The expected number of events in the detection of supernova neutrinos is calculated for the LVD detector leading to an upper limit for the electron neutrino energy of particular importance in this experiment. 25.30.Pt, 26.50.+x A careful knowledge of the semileptonic weak interactions in nuclei allows the possibility of testing implications of physics beyond the standard model, such as exotic properties of neutrino oscillations and massiveness. The dynamics of supernova collapse and explosions as well as the synthesis of heavy nuclei are strongly dominated by neutrinos. For example, neutrinos carry away about 99% of gravitational binding energy in the core-collapse of a massive star, and only a small fraction (∼ 1%) is transferred to the stalled shock front, creating ejected neutrino fluxes observed in supernova remnants .
Nucleosynthesis in Massive Stars with Improved Nuclear and Stellar Physics
The Astrophysical Journal, 2002
We present the first calculations to follow the evolution of all stable nuclei and their radioactive progenitors in stellar models computed from the onset of central hydrogen burning through explosion as Type II supernovae. Calculations are performed for Pop I stars of 15, 19, 20, 21, and 25 M ⊙ using the most recently available experimental and theoretical nuclear data, revised opacity tables, neutrino losses, and weak interaction rates, and taking into account mass loss due to stellar winds. A novel "adaptive" reaction network is employed with a variable number of nuclei (adjusted each time step) ranging from ∼ 700 on the main sequence to 2200 during the explosion. The network includes, at any given time, all relevant isotopes from hydrogen through polonium (Z = 84). Even the limited grid of stellar masses studied suggests that overall good agreement can be achieved with the solar abundances of nuclei between 16 O and 90 Zr. Interesting discrepancies are seen in the 20 M ⊙ model and, so far, only in that model, that are a consequence of the merging of the oxygen, neon, and carbon shells about a day prior to core collapse. We find that, in some stars, most of the "p-process" nuclei can be produced in the convective oxygen burning shell moments prior to collapse; in others, they are made only in the explosion. Serious deficiencies still exist in all cases for the p-process isotopes of Ru and Mo.