Thermonuclear heating of accreting neutron stars

Abstract

We describe a new method to incorporate thermonuclear heating in the envelope of accreting neutron stars into long-term simulations of their thermal evolution. We obtain boundary conditions for the heat exchange between the envelope and the crust based on stationary models, which include nuclear burning, and validate these values by comparing them to the results of the time-dependent code MESA. These simple boundary conditions allow us to explore a large parameter space. We quantify the amount of heat flowing from the envelope into the crust, or vice versa, depending on the mass accretion rate, outburst duration, and duty cycle, and especially crust/core physical parameters such as impurities, crustal heating, and neutrino cooling rate.

M.N.-C. acknowledges the support from a fellowship of CONACYT. M.N.-C.'s work was also supported by the Fonds de la Recherche Scientifique-FNRS under grant No. IISN 4.4502.19. M.N.-C. and D.P.’s work is also supported by a UNAM-DGAPA grant PAPIIT-IN114424. Y.C. acknowledges support from the grant RYC2021-032718-I, financed by MCIN/AEI/10.13039/501100011033 and the European Union NextGenerationEU/PRTR. We thank the referee for the useful suggestions, which helped improve this manuscript.

Postprint (published version)