Soft Gamma-ray Pulsars

Abstract

We propose a model to explain the X-ray and soft gamma-ray spectra and light curves of a class of young pulsars, PSR B1509-58, PSR J1846-0258, PSR J1811-1925, PSR J1617-5055 and PSR J1930+1852. These five spin-down powered pulsars have similar shapes of pulse profiles and spectra of non-thermal X-ray, which can be described by power law with photon index around 1.2. None of them has multi-GeV photon detected. In the outer gap model, most pairs inside the gap are created around the null charge surface and the gap’s electric field separates the two charges to move in opposite directions. Consequently, the region from the null charge surface to the light cylinder is dominated by the outflow of particles and that from the null charge surface to the star is dominated by the inflow of particles. These particles emit curvature photons, and the incoming curvature photons are converted by the strong magnetic field of the neutron star to pairs. We suggest that the outgoing curvature photons of the five pulsars are missed by the lines of sight, and the X-rays and soft gamma-rays of them are the synchrotron radiation of the pairs generated by the magnetic field.