The γ-process nucleosynthesis in core-collapse supernovae II. Effect of the explosive recipe

Context. The γ process in core-collapse supernovae (CCSNe) can produce a number of neutron-deficient stable isotopes heavier than iron ( p nuclei). However, current model predictions do not fully reproduce solar abundances, especially for 92, 94 Mo and 96, 98 Ru. Aims. We investigate the impact of different explosion energies and parametrizations on the nucleosynthesis of p nuclei, by studying stellar models with different initial masses and different CCSN explosions. Methods. We compared the p -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 the p -nucleus production in two sets of CCSN models with initial masses of 15, 20, and 25 M ⊙ 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 total p -nucleus yields are only marginally affected by the CCSN explosion prescriptions if the γ -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, the γ -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 the p -nucleus production with the explosion energy is more complicated if we look at the production of single p nuclei. The light p -nuclei tend to be the most enhanced with increasing explosion energy. In particular, for the CCSN models where the α -rich freeze-out component is ejected, the yields of the lightest p nuclei (including 92, 94 Mo and 96 Ru) 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 of p nuclei. Unlike previous expectations and recent results in the literature, we find that the average production of p nuclei tends to increase with the explosion energy. We also confirm that the pre-explosion production of p nuclei 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 of p nuclei.