The cooling of quasi-persistent neutron star transients
Michigan State University
Neutron star transients with outburst durations of several years allow observations to constrain the cooling rate of the heated neutron star crust. Pycnonuclear reactions in the crust heat the neutron star interior and can elevate the crust temperature considerably with respect to that of the core if the thermal conductivity is sufficiently low. For various scenarios of the physics of the crust and core, we have computed families of quiescent lightcurves for different outburst durations, accretion rates, and quiescent intervals. I will compare these lightcurves with observations, and highlight recent efforts to compute the nuclear reaction chains in the crust for a realistic distribution of rp-process ashes. The unstable ignition of carbon, which powers superbursts, is strongly dependent on the temperature in the neutron star crust and is thus also sensitive to the physics of the crust and core. Interestingly, KS1731-260 had at least one superburst during its protracted accr!
etion outburst but also had a rapidly declining quiescent luminosity. I will compare the superburst ignition conditions from our time-dependent calculations with observations.
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