Large collection of astrophysical S-factors and its compact representation

TL;DR

This paper presents a large, compact database of astrophysical S-factors for about 5000 nuclear reactions relevant to neutron star crust phenomena, using an analytic model for easy interpolation and uncertainty estimation.

Contribution

It extends previous S-factor databases with a new, compact analytic parameterization applicable to a wide range of isotopic reactions in dense astrophysical environments.

Findings

Created a database of ~5000 reactions with S-factors.

Developed an analytic S(E) model with three parameters per reaction.

Demonstrated the model's use in uncertainty estimation for neutron star reactions.

Abstract

Numerous nuclear reactions in the crust of accreting neutron stars are strongly affected by dense plasma environment. Simulations of superbursts, deep crustal heating and other nuclear burning phenomena in neutron stars require astrophysical S-factors for these reactions (as a function of center-of-mass energy E of colliding nuclei). A large database of S-factors is created for about 5000 non-resonant fusion reactions involving stable and unstable isotopes of Be, B, C, N, O, F, Ne, Na, Mg, and Si. It extends the previous database of about 1000 reactions involving isotopes of C, O, Ne, and Mg. The calculations are performed using the Sao Paulo potential and the barrier penetration formalism. All calculated S-data are parameterized by an analytic model for S(E) proposed before [Phys. Rev. C 82, 044609 (2010)] and further elaborated here. For a given reaction, the present S(E)-model contains three parameters. These parameters are easily interpolated along reactions involving isotopes of the same elements with only seven input parameters, giving an ultracompact, accurate, simple, and uniform database. The S(E) approximation can also be used to estimate theoretical uncertainties of S(E) and nuclear reaction rates in dense matter, as illustrated for the case of the 34Ne+34Ne reaction in the inner crust of an accreting neutron star.