Westerlund 1

Westerlund 1 is a young massive stellar cluster in our Galaxy. The H.E.S.S. source HESS J1646–458 emitting very-high-energy gamma-rays is centered on the positon of Westerlund 1. Hence Westerlund I is the likely source of the observed very-high-energy gamma-rays. HESS J1646–458 does not show any cut-off at TeV energies making it a promising PeVatron candidate, i.e. a source where cosmic rays are accelerated up to PeV-energies. Proving that Westerlund 1 is a PeVatron would solve one of the main mysteries in high-energy astrophysics.

The use of the sample mode readout mode with H.E.S.S. is promising to improve the sensitivity at the highest energies helping to investigate a potential cut-off of the energy spectrum.