Interactions of type I X-ray bursts with thin accretion disks

Abstract

Careful observations of X-ray spectra during type I X-ray bursts have hinted at changes occurring in the inner regions of the accretion disks around the neutron-star component of the binary system. Here, we perform a set of numerical experiments studying the interaction of such bursts with thin, Shakura–Sunyaev-type accretion disks. We now clearly demonstrate a number of key effects that take place simultaneously, including evidence for weak, radiation-driven outflows along the surface of the disk; substantial levels of Poynting–Robertson (PR) drag, leading to enhanced accretion; and prominent heating in the disk, which increases the height, while lowering the density and optical depth. The PR drag causes the inner edge of the disk to retreat from the neutron-star surface toward larger radii and then recover on the timescale of the burst. We conclude that the rich interaction of an X-ray burst with the surrounding disk provides a novel way to study the physics of accretion onto compact objects. Fragile et al. study the physics of accretion onto a neutron star from a thin accretion disk when interacting with an X-ray burst. A number of processes occur in the inner disk, including a reflexive retreat of the inner edge of the disk from the star, on the timescale of the burst.