Gamma-Ray and Radio Observations of PSR B1509-58

Abstract

We report concurrent radio and gamma-ray observations of PSR B1509 - 58 carried out by the Parkes Radio Telescope and by the Burst and Transient Source Experiment (BATSE) and the Oriented Scintillation Spectrometer Experiment (OSSE) on the Compton Gamma-Ray Observatory (CGRO). Gamma-ray light curves fitted at several energies between ∼20 and 500 keV yield a phase offset with respect to the radio pulse that is independent of energy, with an average value 0.32±0.02. Although this value is larger by 0.07 than that reported by Kawai et al., the difference is not statistically significant (only ∼2 σ) when account is taken of the uncertainty associated with their result. We briefly discuss the possibility that the energy independence of the gamma-ray pulse phase is a signature of nonthermal radiation in the X-ray/gamma-ray range and the suggestion of a dependence of pulsar radio-gamma-ray phase offset on pulse period.