X-ray observations of unidentified H.E.S.S. γ-ray sources

In a survey of the inner part of the Galaxy, performed with the H.E.S.S. Instrument (High energy stereoscopic system) in 2004 and 2005, a large number of new unidentified very high energy (VHE) γ-ray sources above an energy of 100 GeV was discovered. Often the γ-ray spectra in these sources reach energies of up to ∼ 10 TeV These are the highest energy particles ever attributed to single astrophysical objects. While a few of these sources can be identified at other wavebands, most of these sources remain unidentified so far. A positive identification of these new γ-ray sources with a counterpart object at other wavebands requires a) a positional coincidence between the two sources, b) a viable γ-ray emission mechanism and c) a consistent multiwavelength behaviour of the two sources. X-ray observations with satellites such as XMM-Newton, Chandra or Suzaku provide one of the best channels to studying these enigmatic γ-ray sources at other wavebands, since they combine high angular resolution and sensitivity with the ability to access non-thermal electrons through their synchrotron emission. We therefore have started a dedicated programme to investigate VHE γ-ray sources with high-sensitivity X-ray instruments