The Pulsed Hard X-Ray Spectrum of PSR B1509-58

OSSE observed the 150 ms X-ray pulsar PSR B1509\Gamma58 in the supernova remnant MSH 15\Gamma52 for four weeks in 1992. The pulsed spectrum from 50 keV to 5 MeV is well-fit by a single power law photon spectrum of the form (3:14 \Sigma 0:16) \Theta 10 \Gamma6 \Theta (E=118:5 keV) \Gamma1:68\Sigma0:09 photons cm \Gamma2 s \Gamma1 keV \Gamma1 . 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 two times higher than we observe in the ¸ 55 -- 170 keV energy band. This requires a break to a steeper spectrum somewhere in the intermediate energy range (¸ 40 -- 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. Subject headings: gamma rays: observations --- pulsars: individual (PSR B1509\Gamma58) --- X-rays: stars 1 Mailing addr..