Impact of Coulomb correction factor on rate of change of lepton fraction during presupernova evolution

Abstract

We re-examine the weak interaction nuclei having largest contribution to the lepton-to-baryon fraction (Ye) by coupling the stellar weak rates and mass abundances for post silicon burning conditions during the presupernova evolution of massive stars. The stellar weak rates were recently calculated by Nabi et al. (2021) employing the fully microscopic pn-QRPA model without invoking the Brink-Axel hypothesis. We compute the mass abundances for a total of 728 nuclei, with A = 1–100, using Saha's equation and assuming nuclear statistical equilibrium with the incorporation of Coulomb correction factor to the chemical potential. We compile a list of top 50 electron capture (ec) and β-decay (bd) nuclei, on the basis of largest contribution to Y˙e for post silicon burning conditions, where 11 ec and 6 bd nuclei debuted due to Coulomb corrections. The calculated mass abundances and corresponding Y˙e values are enhanced up to 3 orders of magnitude for heavier nuclei once Coulomb corrections were incorporated. This enhancement led to an increment in total Y˙ebd and Y˙eec values, at Ye = 0.425 (ρ = 2.20×109 g/cm3), of 80% and 91%, respectively. After incorporating the Coulomb corrections, we propose a revised interval of Ye = 0.423-0.455, where bd rates surpass the competing ec rates, and is 3.2% bigger than the one suggested by Nabi et al. (2021).