Fermi Gamma-ray Space Telescope

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

Ignasi Reichardt

Abstract:

The Cygnus Loop is a nearby supernova remnant (SNR) observed across the electromagnetic spectrum, and a bright and very extended source for Fermi/LAT. We report on a comprehensive multi-wavelength study of this object, focused on a reanalysis of the 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. Moreover, we find that in the south-west of the SNR, where the radio emission is strongly and distinctly polarized, the gamma-ray spectrum is harder than for the rest of the shell. We discuss possible scenarios that could explain these spectral differences.