Properties of the pulsar GX 301-2 in the hard x-ray range

In 1993-1994, we performed a series of observations of the X-ray pulsar GX 301-2 with the HEXE instrument of the Mir-Kvant Observatory. We measured the period of the source (it varied between 675 and 678 s) and constructed the pulse profiles in various bands of the energy range 20-75 keV. The measured 20-100-keV luminosity varied between 8 x 10^34 and 7 x 10^35 d^2 erg s-1 (for a point source at distance d kpc). The observed spectrum can be described quite satisfactorily by the `canonical' model for X-ray pulsars with gamma = 1.3, E_c ~ 23keV, and E_f ~ 9 keV. The spectrum changed little from measurement to measurement, but at maximum light, it was slightly softer than that in all the other states. We detected significant variations of the hardness with pulse phase, but the accumulated data were not enough to study the related variations in the spectral parameters. The spectrum exhibited no statistically significant traces of cyclotron lines. The interpretation of the pulse profiles in terms of the model of a rotating neutron star with two emitting polar caps that includes gravitational effects indicates that the most probable inclination of the pulsar's magnetic axis with respect to its spin axis is 40 deg - 70 deg, and that the angle between the observer's direction and the spin axis is ~75 deg - 85 deg.