Studying neutron stars in binaries with large thermonuclear explosions

Hydrogen and helium accreted on a neutron star can undergo unstable thermonuclear burning, which is observable as a flash of X-rays. When fuel is accreted continuously, X-ray bursts occur with recurrence times of hours or days. We discuss what determines this timescale and show the puzzling observations of bursts with recurrence times of only minutes. Hydrogen and helium burning builds up a carbon-rich layer that extends down to the neutron star crust. When this layer burns in a flash, a so-called superburst can be observed. These are much rarer events than ordinary bursts. We place constraints on the suoerburst recurrence time of nine sources and show how they can be used to constrain models of the neutron star interior.