Two binary cycles of GX 301-2
The slow X-ray pulsar, GX 301-2, has been observed throughout two full binary cycles of 41.5 days in the energy range 13-170 keV by the UCSD/MIT Hard X-Ray and Low Energy Gamma-Ray Experiment aboard HEAO 1. Increased intensity and variability was observed for about four days near periastron during the two binary cycles, which were separated by six months in 1978. The spectral shape was not observed to vary with binary phase, with the possible exception of a steepening of the continuum above 20 keV near superior conjunction in one of the two observing epochs. Evidence for a spectral line was found in the data at the 1-percent confidence level, but not confirmed in the remaining data. The temporal variability of GX 301-2 was not consistent with simple models of X-ray production by interaction of the stellar wind with the neutron star, implying that future modeling must include effects on wind density and speed caused by shocks in the wind, the X-ray flux from the neutron star, the gravitational influence of the neutron star, and possible mass accumulation near the neutron star.