Discovery of gamma-ray emission from the shell-type supernova remnant RCW 86 with H.E.S.S

TL;DR

This paper reports the discovery of very high energy gamma-ray emission from the supernova remnant RCW 86 using H.E.S.S., revealing extended emission and providing insights into its possible particle acceleration mechanisms.

Contribution

First detection of VHE gamma-ray emission from RCW 86 with detailed morphological and spectral analysis using H.E.S.S.

Findings

RCW 86 detected at 8.5 sigma significance

Gamma-ray flux is about 10% of the Crab nebula

Gamma-ray emission is more extended than the H.E.S.S. point spread function

Abstract

The shell-type supernova remnant (SNR) RCW 86, possibly associated with the historical supernova SN 185, with its relatively large size (about 40' in diameter) and the presence of non-thermal X-rays is a promising target for gamma-ray observations. The high sensitivity, good angular resolution of a few arc minutes and the large field of view of the High Energy Stereoscopic System (H.E.S.S.) make it ideally suited for the study of the gamma-ray morphology of such extended sources. H.E.S.S. observations have indeed led to the discovery of the SNR RCW 86 in very high energy (VHE; E > 100 GeV) gamma-rays. With 31 hours of observation time, the source is detected with a statistical significance of 8.5 sigma and is significantly more extended than the H.E.S.S. point spread function. Morphological studies have been performed and show that the gamma-ray flux does not correlate perfectly with the X-ray emission. The flux from the remnant is ~10% of the flux from the Crab nebula, with a similar photon index of about 2.5. Possible origins of the very high energy gamma-ray emission, via either Inverse Compton scattering by electrons or the decay of neutral pions produced by proton interactions, are discussed on the basis of spectral features obtained both in the X-ray and gamma-ray regimes.