Physically-Motivated Uncertainty Analysis and Simulation of Nuclear Reactions in X-ray Bursts: Insights from TALYS and CINA

X-ray bursts occur when material from a main sequence star is pulled by gravity onto the surface of a neutron star and causes a thermonuclear explosion. It is critical to understand the nuclear reactions that power these events. Theoretical predictions of nuclear reactions important in X-ray bursts and other astrophysical scenarios are critical to guide measurements but have many challenges. Identifying a range of reaction cross section uncertainties based on uncertainties of the structure of these nuclei would help focus simulations and experiments using these predictions, and are preferred over assigning arbitrary uncertainties such as a factor of 10 or 100.

We used the TALYS reaction code to predict total and partial cross sections using eight different nuclear inputs in the form of alpha-nucleus optical models. These cross section predictions were entered into the Computational Infrastructure for Nuclear Astrophysics (CINA) to simulate the nucleosynthesis occurring in an X-ray burst. In this study, we focused on the reactions ³⁴Ar(α,p)³⁷K , ²²Mg(α,p)²⁵Al, ¹⁸Ne(α,p)²¹Na, ³⁰S(α,p)³³Cl, and ²⁶Si(α,p)²⁹P. Our approach generates more realistic uncertainties in TALYS cross section predictions. Predictions that are used in CINA to estimate uncertainties in the nuclear energy generation rate in X-ray bursts and then compared to the light curves in the Multi-INstrument Burst ARchive (MINBAR). We also use the partial cross sections at multiple energies to identify trends within each predictive optical model.