Models of crustal heating in accreting neutron stars

Aims. Heating associated with non-equilibrium nuclear reactions in accreting neutron-star crusts is reconsidered, taking into account suppression of neutrino losses demonstrated recently by Gupta et al. Two initial compositions of the nuclear burning ashes, Ai = 56 and Ai = 106, are considered. Dependence of the integrated crustal heating on uncertainties plaguing pycnonuclear reaction models is studied. Methods. One-component plasma approximation is used, with compressible liquid-drop model of Mackie and Baym to describe nuclei. Evolution of a crust shell is followed from 10 g cm to 10 g cm. Results. The integrated heating in the outer crust agrees nicely with results of self-considtent multicomponent plasma simulations of Gupta et al.; their results fall between our curves obtained for Ai = 56 and Ai = 106. Total crustal heat per one accreted nucleon ranges between 1.5 MeV/nucleon to 1.9 MeV/nucleon for Ai = 106 and Ai = 56, respectively. The value of Qtot depends weakly on the presence of pycnonuclear reactions at 10 12 −10 g cm. Remarkable insensitivity of Qtot on the details of the distribution of nuclear processes in accreted crust is explained.