A Search for Pulsars between 0.3 and 8 MeV using INTEGRAL

TL;DR

This study used the INTEGRAL satellite to search for gamma-ray emissions from pulsars in the 0.3-8 MeV range, setting upper limits on fluxes and contributing to understanding pulsar spectra.

Contribution

First calibration of INTEGRAL SPI spectrometer for pulsar gamma-ray observations, providing upper limits on pulsar fluxes in the 0.3-8 MeV range.

Findings

Detected Crab and Vela pulsars; no other sources found.

Set upper limits on fluxes for 15 pulsars, mostly below previous limits.

Some pulsars detected above 100 MeV by FERMI have constrained spectra at lower energies.

Abstract

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.