The Thermal Evolution following a Superburst on an Accreting Neutron Star

Superbursts are very energetic Type I X-ray bursts discovered in recent years by long term monitoring of X-ray bursters, and believed to be due to unstable ignition of carbon in the deep ocean of the neutron star. In this Letter, we follow the thermal evolution of the surface layers as they cool following the burst. The resulting light curves agree very well with observations for layer masses in the range 1025–1026 g expected from ignition calculations, and for an energy release & 1017 erg per gram during the flash. We show that at late times the cooling flux from the layer decays as a power law F ∝ t−4/3, giving timescales for quenching of normal Type I bursting of weeks, in good agreement with observational limits. We show that simultaneous modelling of superburst lightcurves and quenching times promises to constrain both the thickness of the fuel layer and the energy deposited. Subject headings: accretion, accretion disks-X-rays:bursts-stars:neutron