An OSSE search for the binary radio pulsar 1259-63

We have searched data from the Oriented Scintillation Spectrometer Experiment (OSSE) on the Compton Gamma Ray Observatory (GRO) for evidence of low-energy γ-ray emission from the binary radio pulsar PSR 1259-63. This 47 ms pulsar is in a long-period, highly eccentric orbit around a Be stellar companion and was observed by OSSE approximately 400 days after periastron. The period derivative allowed by the published radio ephemeris (Johnston et al. 1992) suggests that the pulsar might be relatively young, and therefore a γ-ray source. However, the ephemeris is not sufficiently accurate to allow the traditional epochfolding technique over the full OSSE observation. Instead, the OSSE data were analyzed using Fourier transform spectral techniques after applying trial accelerations to correct for a range of possible orbital accelerations. We searched 48 accelerations; each FFT was 2 ²⁹ points sampled at 2 ms, spanning ∼ 10 ⁶ seconds of observation time. There was no evidence of pulsed emission in the 64-150 keV band, with a 99.9% confidence upper limit of 6 × 10 ^-3 photons cm ^-2 s ^-1 MeV ^-1 . or ∼40 mCrab pulsars, which suggests that the pulsar's intrinsic period derivative is small and its magnetic field weak. This work was performed on the Concurrent Supercomputing Consortium's Intel Touchstone Delta parallel supercomputer as part of a GRO Phase 1 Guest Investigation.