The effect of the infrared excess from the Be star on inverse Compton gamma-ray production in PSR B1259-63/SS 2883

TL;DR

This paper investigates how infrared emission from a Be star influences inverse Compton gamma-ray production in the PSR B1259-63 system, finding that infrared increases the gamma-ray flux by over double.

Contribution

It introduces a model incorporating infrared emission effects into inverse Compton gamma-ray calculations for PSR B1259-63.

Findings

Infrared emission from the Be star enhances gamma-ray flux by a factor of at least 2.

The study uses a curve of growth method fitted to optical and infrared data.

Exact scattering calculations confirm the significant impact of infrared photons.

Abstract

The binary system PSR B1259-63 consists of a 48 ms pulsar in a 3.4 year orbit around a Be star and unpulsed TeV gamma-ray emission has been detected near previous periastron passages. A likely source of the gamma-rays is the inverse Compton up-scattering of target photons from the Be star by the ultra-relativistic electron/positron pulsar wind in the region of the plerion shock front. In this study the effect of the infrared emission from the Be star's circumstellar disc on inverse Compton gamma-ray production in PSR B1259-63 is investigated by considering an isotropic photon/electron approximation. The modified photon density distribution is determined by using a curve of growth method fitted to previous optical and infrared observations. The inverse Compton scattering rate is calculated using the modified photon distribution and the exact scattering equation. It is shown that including the infrared emission increase the GeV gamma-ray flux by a factor $\ga 2$.