OSSE Observations of X-Ray Pulsars

We report on OSSE observations of the Be binary pulsars A0535+26, GRO J1008--57, and 4U 0115+63 at energies above 50 keV. The spectra are generally thermal, with exponential folding energies of 15--25 keV, and no evidence for hard power-law tails. We have clearly detected a strong cyclotron absorption line at 110 keV from A0535+26 [1], and we find a suggestion of an absorption line near 90 keV from GRO J1008--57. Introduction We report on GRO/OSSE observations of three X-ray pulsars with Betype stellar companions, namely A0535+26, GRO J1008--57, and 4U 0115+63. Be binary systems are known to be transient hard X-ray emitters, with the increased emission usually interpreted as episodic mass transfer to the neutron star from the Be companion. Outbursts may vary dramatically in intensity from orbit to orbit, and they can last for a significant fraction of the binary period. A0535+26 The Be binary A0535+26 is a recurrent transient pulsar with pulse period ß104 s and recurrence period ß..