Fermi/LAT Study of the Cygnus Loop Supernova Remnant: Discovery of a Point-like Source and of Spectral Differences in its gamma-ray emission

TL;DR

This study analyzes 6 years of Fermi/LAT data of the Cygnus Loop SNR, revealing a point-like gamma-ray source and spectral differences that shed light on the remnant's interaction with its environment.

Contribution

It identifies a previously unresolved point-like gamma-ray source and distinguishes spectral variations within the Cygnus Loop SNR using spatially resolved gamma-ray data.

Findings

Discovery of a point-like gamma-ray source southeast of the SNR

Spectral differences correlated with polarization regions

Extended emission aligns with thermal X-ray emission

Abstract

The Cygnus Loop is a nearby supernova remnant (SNR) observed across the electromagnetic spectrum. With the analysis of 6 years of Fermi/LAT data we find that, what previous studies had considered a single source, consists of an extended source plus a point-like source south-east of the SNR. The extended gamma-ray emission is well correlated with the thermal X-ray emission of the SNR, and the energy spectrum displays a pronounced maximum at $\sim0.6$\,GeV. However, in a region where the radio emission is strongly and distinctly polarized, the gamma-ray spectrum shows no sign of a break. Therefore, the spatially resolved gamma-ray emission permits the study of different interaction conditions of the SNR and the surrounding medium.