Explosive Nucleosynthesis In Supernovae Research Articles

The ν-Process in the Light of an Improved Understanding of Supernova Neutrino Spectra

Abstract We study the neutrino-induced production of nuclides in explosive supernova nucleosynthesis for progenitor stars with solar metallicity including neutrino-nucleus reactions for all nuclei with charge numbers Z < 76, with average neutrino energies in agreement with modern supernova simulations. Considering progenitors with initial main sequence masses between 13 M ⊙ and 30 M ⊙, we find a significant production of 11B, 138La, and 180Ta by neutrino nucleosynthesis, despite the significantly reduced neutrino energies. The production of 19F turns out to be more sensitive to the progenitor mass and structure than to the ν-process. With our complete set of cross sections we have identified the effects of the ν-process on several stable nuclei including 33S, 40Ar, 41K, 59Co, and 113In at the 10% level. Neutrino-induced reactions contribute to a similar extent to the production of radioactive 26Al and increase the yield of 22Na by 50%. Future γ-ray astronomy missions may reach the sensitivity at which the contribution from the ν-process becomes relevant. We find that the production of 22Na by the ν-process could explain the Ne-E(L) component of meteoritic graphite grains. The ν-process enhances the yield of 36Cl and we point out that the resulting 36Cl/35Cl ratio is in agreement with the values inferred for the early solar system. Our extended set of neutrino-nucleus interactions also allows us to exclude any further effects of the ν-process on stable nuclei and to quantify the effects on numerous, hitherto unconsidered radioactive nuclei, e.g., 36Cl, 72As, 84Rb, and 88Y.

ALMA spectral survey of Supernova 1987A – molecular inventory, chemistry, dynamics and explosive nucleosynthesis

We report the first molecular line survey of Supernova 1987A in the millimetre wavelength range. In the ALMA 210--300 and 340--360 GHz spectra, we detected cold (20--170 K) CO, 28SiO, HCO+ and SO, with weaker lines of 29SiO from ejecta. This is the first identification of HCO+ and SO in a young supernova remnant. We find a dip in the J=6--5 and 5--4 SiO line profiles, suggesting that the ejecta morphology is likely elongated. The difference of the CO and SiO line profiles is consistent with hydrodynamic simulations, which show that Rayleigh-Taylor instabilities cause mixing of gas, with heavier elements much more disturbed, making more elongated structure. We obtained isotopologue ratios of 28SiO/29SiO>13, 28SiO/30SiO>14, and 12CO/13CO>21, with the most likely limits of 28SiO/29SiO>128, 28SiO/30SiO>189. Low 29Si and 30Si abundances in SN 1987A are consistent with nucleosynthesis models that show inefficient formation of neutron-rich isotopes in a low metallicity environment, such as the Large Magellanic Cloud. The deduced large mass of HCO+ (~5x10^-6 Msun) and small SiS mass (<6x10^-5 Msun) might be explained by some mixing of elements immediately after the explosion. The mixing might have caused some hydrogen from the envelope to sink into carbon and oxygen-rich zones after the explosion, enabling the formation of a substantial mass of HCO+. Oxygen atoms may have penetrated into silicon and sulphur zones, suppressing formation of SiS. Our ALMA observations open up a new window to investigate chemistry, dynamics and explosive-nucleosynthesis in supernovae.

ALMA observations of Molecules in Supernova 1987A

AbstractSupernova (SN) 1987A has provided a unique opportunity to study how SN ejecta evolve in 30 years time scale. We report our ALMA spectral observations of SN 1987A, taken in 2014, 2015 and 2016, with detections of CO, 28SiO, HCO+ and SO, with weaker lines of 29SiO.We find a dip in the SiO line profiles, suggesting that the ejecta morphology is likely elongated. The difference of the CO and SiO line profiles is consistent with hydrodynamic simulations, which show that Rayleigh-Taylor instabilities causes mixing of gas, with heavier elements much more disturbed, making more elongated structure.Using 28SiO and its isotopologues, Si isotope ratios were estimated for the first time in SN 1987A. The estimated ratios appear to be consistent with theoretical predictions of inefficient formation of neutron rich atoms at lower metallicity, such as observed in the Large Magellanic Cloud (about half a solar metallicity).The deduced large HCO+ mass and small SiS mass, which are inconsistent to the predictions of chemical model, might be explained by some mixing of elements immediately after the explosion. The mixing might have made some hydrogen from the envelope to sink into carbon and oxygen-rich zone during early days after the explosion, enabling the formation of a substantial mass of HCO+. Oxygen atoms may penetrate into silicon and sulphur zone, suppressing formation of SiS.Our ALMA observations open up a new window to investigate chemistry, dynamics and explosive-nucleosynthesis in supernovae.

SILICON CARBIDE GRAINS OF TYPE C PROVIDE EVIDENCE FOR THE PRODUCTION OF THE UNSTABLE ISOTOPE 32 Si IN SUPERNOVAE

Carbon-rich grains are observed to condense in the ejecta of recent core-collapse supernovae, within a year after the explosion. Silicon carbide grains of type X are C-rich grains with isotpic signatures of explosive supernova nucleosynthesis have been found in primitive meteorites. Much rarer silicon carbide grains of type C are a special sub-group of SiC grains from supernovae. They show peculiar abundance signatures for Si and S, isotopically heavy Si and isotopically light S, which appear to to be in disagreement with model predictions. We propose that C grains are formed mostly from C-rich stellar material exposed to lower SN shock temperatures than the more common type X grains. In this scenario, extreme $^{32}$S enrichments observed in C grains may be explained by the presence of short-lived $^{32}$Si ($\tau$$_{1/2}$ = 153 years) in the ejecta, produced by neutron capture processes starting from the stable Si isotopes. No mixing from deeper Si-rich material and/or fractionation of Si from S due to molecular chemistry is needed to explain the $^{32}$S enrichments. The abundance of $^{32}$Si in the grains can provide constraints on the neutron density reached during the supernova explosion in the C-rich He shell material. The impact of the large uncertainty of the neutron capture cross sections in the $^{32}$Si region is discussed.

Evaluation of electron capture reaction rates in Ni isotopes in stellar environments

Electron capture rates in Ni isotopes are studied in stellar environments, that is, at high densities and high temperatures during the core-collapse and postbounce explosive nucleosynthesis in supernovae. Reaction rates in $^{58}\mathrm{Ni}$ and $^{60}\mathrm{Ni}$, as well as in $^{56}\mathrm{Ni}$, $^{62}\mathrm{Ni}$, and $^{64}\mathrm{Ni}$, are evaluated by shell-model calculations with the use of a new shell-model Hamiltonian in the $\mathit{fp}$ shell, GXPF1J. While the previous shell-model calculations failed to reproduce the measured peaks of Gamow-Teller strength in $^{58}\mathrm{Ni}$ and $^{60}\mathrm{Ni}$, the present new Hamiltonian is found to reproduce them very well, as well as the capture rates obtained from the observed strengths. Strengths and energies of the Gamow-Teller transitions in $^{56}\mathrm{Ni}$, $^{62}\mathrm{Ni}$, and $^{64}\mathrm{Ni}$ are also found to be consistent with the observations.

On the origin of the helium-rich population in ω Centauri

To study the possible origin of the huge helium enrichment attributed to the stars on the blue main sequence of ω Centauri, we make use of a chemical evolution model that has proven able to reproduce other major observed properties of the cluster, namely its stellar metallicity distribution function, age–metallicity relation and trends of several abundance ratios with metallicity. In this framework, the key condition to satisfy all the available observational constraints is that a galactic-scale outflow develops in a much more massive parent system, as a consequence of multiple supernova explosions in a shallow potential well. This galactic wind must carry out preferentially the metals produced by explosive nucleosynthesis in supernovae, whereas elements restored to the interstellar medium through low-energy stellar winds by both asymptotic giant branch (AGB) stars and massive stars must be mostly retained. Assuming that helium is ejected through slow winds by both AGB stars and fast-rotating massive stars, the interstellar medium of ω Centauri's parent galaxy gets naturally enriched in helium in the course of its evolution.

Fe-peak element abundances in disk and halo stars

AbstractAt present none of galactic chemical evolution (GCE) models provides a self-consistent description of observed trends for all iron-peak elements with metallicity simultaneously. The question is whether the discrepancy is due to deficiencies of GCE models, such as stellar yields, or due to erroneous spectroscopically-determined abundances of these elements in metal-poor stars. The present work aims at a critical reevaluation of the abundance trends for several odd and even-Z Fe-peak elements, which are important for understanding explosive nucleosynthesis in supernovae.

Interstellar SiC with unusual isotopic compositions - Grains from a supernova?

view Abstract Citations (183) References (34) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Interstellar SiC with Unusual Isotopic Compositions: Grains from a Supernova? Amari, Sachiko ; Hoppe, Peter ; Zinner, Ernst ; Lewis, Roy S. Abstract Results are presented from an ion microprobe mass spectrometric analyses of five SiC grains from the Murchison carbonaceous meteorite. Unlike most interstellar SiC grains from primitive meteorites, the five grains from the Murchison meteorite show large excesses of C-12 (up to 28 times solar) and N-15 (up to 22 times solar), depletion in Si-29 and Si-30 (up to 59 percent), Al-26/Al-27 ratios between 0.1 and 0.6, and Ti-49 excesses up to 95 percent; in addition, one grain has a large Ca-44 excess (300 percent). The Ca and Ti anomalies point toward explosive nucleosynthesis in supernovae and the in situ decay of the radioactive precursors Ti-44 and V-49 in SiC grains formed in supernova ejecta. However, there is no simple formation scenario that can give a consistent explanation for the isotopic compositions of these grains. Publication: The Astrophysical Journal Pub Date: August 1992 DOI: 10.1086/186468 Bibcode: 1992ApJ...394L..43A Keywords: Interstellar Matter; Murchison Meteorite; Nuclear Astrophysics; Silicon Carbides; Stellar Mass Ejection; Supernovae; Abundance; Asymptotic Giant Branch Stars; Mass Spectroscopy; Stellar Models; Wolf-Rayet Stars; Astrophysics; ISM: ABUNDANCES; ISM: DUST; EXTINCTION; NUCLEAR REACTIONS; NUCLEOSYNTHESIS; ABUNDANCES; STARS: CARBON; STARS: SUPERNOVAE: GENERAL full text sources ADS | data products SIMBAD (1)

Explosive Nucleosynthesis in Supernovae

Explosive Nucleosynthesis in Supernovae