HESS (High Energy Stereoscopic System), a ground-based Cerenkov array telescopes has been operated since a few years and in 2004 has performed the ?rst Galactic plane scan with a sensitivity of a few percent of the Crab at energies above 100 GeV, resulting in the discoveryofeightsources, mostofwhichwithoutanycounterpartatdifferentenergies 1,2]. ParticularattentionwasdevotedtoHESSJ1813-178, notidenti?edwithanyknownX/gamma ray emitter and hypothesised to be a dark particle accelerator. Independently, and at the same time, INTEGRAL discovered a new soft gamma-ray source, namely IGR J18135-1751,...