Sensitivity studies on the thermal beta+decay and thermal neutrino loss rates in the multizone X-ray burst model mesa

Abstract

ABSTRACT Recently, it has been discovered that the beta+decay rates and neutrino loss rates of 64Ga and 68Se greatly affect the light curves and final abundances of X-ray bursts in a one-zone model in all circumstances. Here we further expand the study to the multizone model mesa and compare the results with observations of the bursting source GS 1826–24. It was found that the light curve of the modified beta decay rates of 64Ga is more comparable to observations than the standard beta decays. The final mass fractions of the ashes of the X-ray bursts for elements with a mass number of 38 (38Ar, 38Ca) are greatly modified because of the beta+decay rate and neutrino loss rate of 68Se. They also produce more URCA nuclei, which may lead to stronger cooling in the neutron star crusts. Both the modified rates of 68Se and 64Ga make the recurrence times of the simulated X-ray bursts longer because they cause more energy loss than the standard rates and more time is needed to accumulate energy to trigger the bursts.