Hard X-Ray Spectra from Gap Accretion onto Neutron Stars

摘要: Weakly magnetized neutron stars undergoing disk accretion are found to emit copious hard X-rays if the marginally stable orbit lies outside stellar surface. In this general relativistic picture (impossible in Newtonian gravity) terminates well Accreting matter crosses gap between and star free fall; it then strikes surface at a shallow angle, creating hot equatorial belt with temperature inversion. A typical emergent spectrum, which was obtained self-consistent manner by one-plus-one-dimensional radiative transfert hydro code, is presented.