Galactic hadronic CR-accelerators as seen with H.E.S.S.

The High Energy Stereoscopic System (H.E.S.S.) is up to now the only facility available for studying the Very High Energy (VHE) sky in the Southern Hemisphere. This gives H.E.S.S. a unique position in investigating the various galactic CR-accelerators by means of their gamma-ray emission. In this talk, we give an overview on the recent detections of VHE-emission from the recurrent nova RS Ophuichi, the young massive stellar cluster Westerlund 1 and the SNRs Kepler and N132D and conclusions that can be drawn upon the efficiency of hadronic CR-acceleration from these sources.

RS Ophuichi underwent its latest eruption in August 2021 and was established by H.E.S.S. as the first recurrent nova with gamma-ray emission extending into the TeV regime. The observations constrain models of time-dependent particle energization, favoring a hadronic origin of the emission.

Westerlund 1 is the most massive known young stellar cluster in our Galaxy and the position of the cluster coincides with the extended VHE source HESS J1646−458. We carried out a deep spectromorphological study of the region and conclude that an association between the cluster and the VHE-emission is viable. In a hadronic scenario, the emission indicates proton-acceleration beyond several 100s of TeV.

Deep observations of the region around Kepler’s SN revealed a gamma-ray excess coincident with the position of Kepler’s SNR. The spectral energy distribution of the SNR emission resembles that of Tycho's SNR, which is at a similar evolutionary stage and likely has sizable hadronic emission at least at lower energies. Further, deep observations of the Oxygen-rich LMC SNR N132D reveal a VHE-spectrum extending beyond 8 TeV with no indication of a cutoff. Its gamma-ray emission is best explained by a dominant hadronic component.