Dependence of X-Ray Burst Models on Nuclear Reaction Rates

TL;DR

This study examines how uncertainties in specific nuclear reaction rates influence the accuracy of X-ray burst models, highlighting key reactions that impact observable features and guiding future nuclear physics research.

Contribution

It introduces a comprehensive method combining single-zone and multi-zone models to identify nuclear reaction rates that critically affect X-ray burst predictions.

Findings

Certain reaction rates significantly alter burst light curves.

Uncertain reaction rates influence the composition of burst ashes.

The study guides future nuclear physics efforts to refine models.

Abstract

X-ray bursts are thermonuclear flashes on the surface of accreting neutron stars and reliable burst models are needed to interpret observations in terms of properties of the neutron star and the binary system. We investigate the dependence of X-ray burst models on uncertainties in (p,$\gamma$), ($\alpha$,$\gamma$), and ($\alpha$,p) nuclear reaction rates using fully self-consistent burst models that account for the feedbacks between changes in nuclear energy generation and changes in astrophysical conditions. A two-step approach first identified sensitive nuclear reaction rates in a single-zone model with ignition conditions chosen to match calculations with a state-of-the-art 1D multi-zone model based on the {\Kepler} stellar evolution code. All relevant reaction rates on neutron deficient isotopes up to mass 106 were individually varied by a factor of 100 up and down. Calculations of the 84 highest impact reaction rate changes were then repeated in the 1D multi-zone model. We find a number of uncertain reaction rates that affect predictions of light curves and burst ashes significantly. The results provide insights into the nuclear processes that shape X-ray burst observables and guidance for future nuclear physics work to reduce nuclear uncertainties in X-ray burst models.