Fermi Study of 5-300 GeV emission from the high-mass pulsar binary PSR B1259-63/LS 2883

TL;DR

This study analyzes Fermi LAT data of the PSR B1259-63/LS 2883 binary, detecting a persistent 5-300 GeV emission component during flares and quiescence, likely from inverse-Compton scattering in the shock region.

Contribution

It provides the first clear detection of a persistent high-energy component in the binary, with detailed spectral analysis and modeling of its origin.

Findings

Detection of 5-300 GeV emission during flares at 5σ significance.

Discovery of the same component during quiescent phases.

The emission is consistent with inverse-Compton scattering from shock-accelerated particles.

Abstract

We report the results from our detailed analysis of the Fermi Large Area Telescope (LAT) data for the pulsar binary PSR B1259-63/LS 2883. During the GeV flares that occurred when the pulsar was in the periastron passages, we have detected a 5--300 GeV component at $\simeq 5\sigma$ in emission from the binary. The detection verifies the presence of the component that has been marginally found in the previous studies of the binary. Furthermore, we have discovered that this component was present even in the quiescent state of the binary, specifically the mean anomaly phase 0.7--0.9. The component can be described by a power law with photon index $\Gamma\sim 1.4$, and the flux in the flares is approximately one order of magnitude higher than that in quiescence. We discuss the origin of this component. It likely arises from the inverse-Compton process: high-energy particles from the shock, due to the interaction between the winds from the pulsar and massive companion, scatter the seed photons from the companion to GeV/TeV energies. Based on this scenario, model fits to the broad-band X-ray--to--TeV spectra of the binary in the flaring and quiescent states are provided.