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Context.Theγprocess in core-collapse supernovae (CCSNe) can produce a number of neutron-deficient stable isotopes heavier than iron (pnuclei). However, current model predictions do not fully reproduce solar abundances, especially for92, 94Mo and96, 98Ru. Aims.We investigate the impact of different explosion energies and parametrizations on the nucleosynthesis ofpnuclei, by studying stellar models with different initial masses and different CCSN explosions. Methods.We compared thep-nucleus yields obtained using a semi-analytical method to simulate the supernova to those obtained using hydrodynamic models. We explored the effect of varying the explosion parameters on thep-nucleus production in two sets of CCSN models with initial masses of 15, 20, and 25M⊙at solar metallicity. We calculated a new set of 24 CCSN models (eight for each stellar progenitor mass) and compared our results with another recently published set of 80 CCSN models that includes a wide range of explosion parameters: explosion energy or initial shock velocity, energy injection time, and mass location of the injection. Results.We find that the totalp-nucleus yields are only marginally affected by the CCSN explosion prescriptions if theγ-process production is already efficient in the stellar progenitors due to a C−O shell merger. In most CCSN explosions from progenitors without a C−O shell merger, theγ-process yields increase with the explosion energy by up to an order of magnitude, depending on the progenitor structure and the CCSN prescriptions. The general trend of thep-nucleus production with the explosion energy is more complicated if we look at the production of singlepnuclei. The lightp-nuclei tend to be the most enhanced with increasing explosion energy. In particular, for the CCSN models where theα-rich freeze-out component is ejected, the yields of the lightestpnuclei (including92, 94Mo and96Ru) increase by up to three orders of magnitude. Conclusions.We provide the first extensive study using different sets of massive stars of the impact of varying CCSN explosion prescriptions on the production ofpnuclei. Unlike previous expectations and recent results in the literature, we find that the average production ofpnuclei tends to increase with the explosion energy. We also confirm that the pre-explosion production ofpnuclei in C−O shell mergers is a robust result, independent of the subsequent explosive nucleosynthesis. More generally, a realistic range of variations in the evolution of stellar progenitors and in the CCSN explosions might boost the CCSN contribution to the galactic chemical evolution ofpnuclei.
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The γ -process nucleosynthesis in core-collapse supernovae: I. A novel analysis of γ -process yields in massive stars
Context. The γ -process nucleosynthesis in core-collapse supernovae is generally accepted as a feasible process for the synthesis of neutron-deficient isotopes beyond iron. However, crucial discrepancies between theory and observations still exist: the average yields of γ -process nucleosynthesis from massive stars are still insufficient to reproduce the solar distribution in galactic chemical evolution calculations, and the yields of the Mo and Ru isotopes are a factor of ten lower than the yields of the other γ -process nuclei. Aims. We investigate the γ -process in five sets of core-collapse supernova models published in the literature with initial masses of 15, 20, and 25 M ⊙ at solar metallicity. Methods. We compared the γ -process overproduction factors from the different models. To highlight the possible effect of nuclear physics input, we also considered 23 ratios of two isotopes close to each other in mass relative to their solar values. Further, we investigated the contribution of C–O shell mergers in the supernova progenitors as an additional site of the γ -process. Results. Our analysis shows that a large scatter among the different models exists for both the γ -process integrated yields and the isotopic ratios. We find only ten ratios that agree with their solar values, all the others differ by at least a factor of three from the solar values in all the considered sets of models. The γ -process within C–O shell mergers mostly influences the isotopic ratios that involve intermediate and heavy proton-rich isotopes with A > 100. Conclusions. We conclude that there are large discrepancies both among the different data sets and between the model predictions and the solar abundance distribution. More calculations are needed; particularly updating the nuclear network, because the majority of the models considered in this work do not use the latest reaction rates for the γ -process nucleosynthesis. Moreover, the role of C–O shell mergers requires further investigation.
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- Award ID(s):
- 1927130
- PAR ID:
- 10464355
- Date Published:
- Journal Name:
- Astronomy & Astrophysics
- Volume:
- 677
- ISSN:
- 0004-6361
- Page Range / eLocation ID:
- A22
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1051/0004-6361/202346556
