THE PULSED HARD X-RAY-SPECTRUM OF PSR B1509-58

OSSE observed the 150 ms X-ray pulsar PSR B1509-58 in the supernova remnant MSH 15-52 for 4 weeks in 1992. The pulsed spectrum from 50 keV to 5 MeV is well represented by a single power-law photon spectrum of the form (3.14 +/- 0.16) x 10(-6) x (E/118.5 keV)(-1.68+/-0.09) photons cm(-2) s(-1) keV(-1). This is significantly harder than the Crab pulsar spectrum in this energy range. The Ginga soft X-ray spectrum (2-60 keV) reported by Kawai et al. is significantly harder than the observed OSSE spectrum and predicts a flux 2 times higher than we observe in the similar to 55-170 keV energy band. This requires a break to a steeper spectrum somewhere in the intermediate energy range (similar to 20-80 keV). The spectrum must soften again at higher energies or the pulsar would have easily been detected by EGRET, COS B, and SAS 2.