Gamow-Teller transitions from 24Mg and its impact on the electron capture rates in the O + Ne + Mg cores of stars

TL;DR

This paper uses the pn-QRPA method to calculate Gamow-Teller transition strengths and electron capture rates for 24Mg, revealing significant differences from previous models and implications for supernova core collapse simulations.

Contribution

It introduces a new calculation of electron capture rates on 24Mg using pn-QRPA, showing enhanced rates compared to shell model predictions.

Findings

Calculated rates differ from previous shell model and F2N rates.

Good agreement with experimental Gamow-Teller strength distributions.

Enhanced electron capture rates up to four times at high temperatures and densities.

Abstract

Electron captures on nuclei play an important role in the collapse of stellar core in the stages leading to a type-II supernova. Recent observations of subluminous Type II-P supernovae (e.g. 2005cs, 2003gd, 1999br) were able to rekindle the interest in 8 - 10 which develop O+Ne+Mg cores. We used the proton-neutron quasiparticle random phase approximation (pn-QRPA) theory to calculate the B(GT) strength for 24Mg \rightarrow 24Na and its associated electron capture rates for incorporation in simulation calculations. The calculated rates, in this letter, have differences with the earlier reported shell model and Fuller, Fowler, Newman (hereafter F2N) rates. We compared Gamow-Teller strength distribution functions and found fairly good agreement with experiment and shell model. However, the GT centroid and the total GT strength, which are useful in the calculation of electron capture rates in the core of massive pre-supernova stars, lead to the enhancement of our rate up to a factor of four compared to the shell model rates at high temperatures and densities.