A Search for Pulsars between 0.3 and 8 MeV using INTEGRAL

The spectra of only a few pulsars are known in the low-energy gamma-ray region around 1 Mev. We searched for point sources of gamma-radiation in the 0.3-1 and 1-8 Mev bandpasses at the location of known radio and X-ray pulsars. Single channel photometry using the SPI spectrometer on INTEGRAL, obtained using a coded-aperture mask, is feasible if calibrated using known fluxes from point sources. The calibration was carried out using the Crab nebula and verified using the Vela pulsar. The locations of a representative sample of pulsar types were then observed. Other than the Crab and Vela pulsars, no sources were detected. Upper limits are given on the time-averaged flux from the location of 15 other pulsars; most lie below previously published upper limits. Six of the pulsars for which we determine upper limits at 1 MeV have been detected above 100 MeV by FERMI. The upper limits we report here help to describe the spectrum of these pulsars at all wavelengths.