Mechanism of the X-ray and Soft Gamma-ray Emissions from High Magnetic Field Pulsar: PSR B1509-58

TL;DR

This paper explains the X-ray and soft gamma-ray emissions of pulsar PSR B1509-58 using the outer gap model, highlighting how pair creation and magnetic fields shape the observed energy-dependent pulse profiles.

Contribution

It applies the outer gap model to PSR B1509-58, revealing how magnetic pair creation and pitch angles influence the pulsar's emission spectra and pulse profiles.

Findings

The second peak at >10MeV originates near the star where magnetic fields are stronger.

Pulse profile differences across energy bands are due to varying pitch angles of secondary pairs.

The model successfully reproduces observed energy-dependent light curves.

Abstract

We use the outer gap model to explain the spectrum and the energy dependent light curves of the X-ray and soft gamma-ray radiations of the spin-down powered pulsar PSR B1509-58. 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 current while that from the null charge surface to the star is dominated by the inflow current. We suggest that the viewing angle of PSR B1509-58 only receives the inflow radiation. The incoming curvature photons are converted to pairs by the strong magnetic field of the star. The X-rays and soft gamma-rays of PSR B1509-58 result from the synchrotron radiation of these pairs. Magnetic pair creation requires a large pitch angle, which makes the pulse profile of the synchrotron radiation distinct from that of the curvature radiation. We carefully trace the pulse profiles of the synchrotron radiation with different pitch angles. We find that the differences between the light curves of different energy bands are due to the different pitch angles of the secondary pairs, and that the second peak appearing at E>10MeV comes from the region near the star, where the stronger magnetic field allows pair creation to happen with a smaller pitch angle.