Nuclear reactions in the crust of an accreting neutron star

Recently there have been many discoveries from observations of accreting neutron stars in x-ray binaries. Many of the observed phenomena such as superbursts or the cooling of quasi-persistent transients during their quiescent state are affected by the thermal properties and the composition of the crust. To model the nuclear energy release and crust compositions, we run a consistent nuclear reaction network that follows the evolution of an accreted fluid element from the atmosphere down to the inner crust, where free neutrons exist in beta-equilibrium. We take into account a majority of the most important nuclear processes including electron capture, neutron capture, neutron emissions, $\beta $ decay, and pycnonuclear fusion reactions. Our calculations show that pycnonuclear fusion reactions can occur at a shallower depth than previously thought, depending on the nuclear mass model used.