Published online by Cambridge University Press: 21 July 2022
Thermal x-rays from neutron stars are mainly radiated by accretion discs originating in the flux of material from a companion star. The companions are white dwarf stars with a range of masses, and some black holes. X-ray bursts are attributed to catastrophic nuclear events on the neutron star surface following accretion from the companion. Structure in the rotating accretion disc is observed as quasi-periodic oscillations (QPOs).