Multi-wavelength observations of H.E.S.S. AGN
  Multi-frequency observations are a powerful tool of astrophysical investigation. Not only is data in each wavelength band providing different clues to the objects nature, but taken simultaneously, these data can reveal the mechanisms at work in astrophysical objects. In the past years, joint multi-frequency observations with the H.E.S.S. telescopes in the very high energy (VHE, E>100GeV) band and several other experiments in the radio, optical, X-ray, and high energy (HE, E>100MeV) bands have lead to intriguing results that will ultimately help answering the open questions of the location of the very high energy emission, details of the acceleration mechanism, and the role of the central black hole. 
Martin Tluczykont (for the H.E.S.S. Collaboration)
astro-ph.HE