Flux and spectrum variability in Her X‐1

Abstract

Hercules X‐1 was observed by the Large Area Counters (LAC) on the Ginga satellite during several periods in 1988 and 1989. The spectrum of Her X‐1 was measured on a timescale of several minutes, and the flux measured on a timescale of a few seconds. Large changes in flux and in spectral shape were observed, on short and on long timescales. The spectrum has been modeled consistently using a model with two continuum components plus iron emission line and absorption by cold matter. Spectral parameters are derived for pre‐eclipse absorption dips and for eclipse ingress. The changes in spectral parameters are given a physical interpretation in terms of the emission region around the neutron star and in terms of the absorbing matter in the system.