X‐ray scattering in x‐ray binary pulsars

Abstract

In x‐ray pulsars, the emission from the bottom of the accretion column in the magnetic pole propagates to the observers through the surrounding environment: the magnetosphere, the accretion disk and the disk corona, the stellar wind, the companion’s atmosphere, and finally the interstellar medium. The photoionization zone of the stellar wind, which is formed surrounding the neutron star by x‐ray irradiation, plays an important role as a reprocessing site. The spectrum originating from the polar caps is modified by the photoelectric absorption and subsequent fluorescent emission, Thomson/Compton scattering and synchrotron resonant scattering that occur in these environments. Modifications in the spectrum due to the reprocessing are briefly reviewed based on the recent results obtained from observations by Tenma, EXOST, and Ginga. A preliminary result from Vela X‐1 with ASCA is presented, exhibiting a new aspect in studying x‐ray pulsars.