Pulse phase studies of x-ray emission from GX301-2

Abstract

Observations of GX301-2 by Tenma have been analyzed to study spectral changes which occur through the 701 second pulse period. Significant spectral dependence on pulse phase is found which varies from observation to observation. Due to the large column densities observed for GX301-2, effects on the observed spectrum caused by scattering in the circumstellar material are important. These were quantified by Monte Carlo simulations. Such effects can account for a significant part, but not all, of the observed variations. The variation of pulse fraction, allowing for scattering effects, implies that the beaming of radiation from the source fluctuates in a way which is not simply dependent on source intensity. Intrinsic dependence on pulse phase is found for spectral index, cutoff energy and e-folding energy. The dependence of spectral index is different for different observations, and shows an asymmetry indicating a significantly non-dipolar magnetic field for GX301-2. The intensity of the iron line has a pulse phase dependence.