WATCH GRANAT OBSERVATIONS OF THE X-RAY PULSAR GX-301-2

Results of observations of the X-ray pulsar GX 301-2 carried out with the WATCH instrument of the GRANAT Orbiting Observatory between Januar y 1990 and October 1993 are reported. The deduced mean light curve of this X-ray source exhibits a flare near orbital phase 0.94, which virt ually terminates before the X-ray source reaches the periastron. The t ime of the X-ray flare derived from the WATCH data has made it possibl e to refine the period of the pulsar's flares. The deduced value, with in the limits of the errors, closely matches the orbital period of GX 301-2 previously obtained from the Doppler shift in the source's rotat ion period. The luminosity of GX 301-2 at maximum light, its mean lumi nosity, and the total energy released by the pulsar during the flare n ear the periastron have been determined. The pulsation period of the s ource during the WATCH observations has been evaluated. The correspond ence of the observed evolution of the rotation period with various acc retion models is checked. The premature turnoff of the flare is interp reted in terms of the formation of a rarefaction zone around the neutr on star due to heating of the stellar wind by X-ray emission from the pulsar during the flare.