INTEGRAL IGR J18135-1751=HESS J1813-178: A new cosmic high energy accelerator from keV to TeV

We report the discovery of a soft gamma ray source, namely IGR J18135-1751, detected with the IBIS imager on board the INTEGRAL satellite. The source is persistent and has a 20-100 keV luminosity of $\sim$5.7 $\times$ 10$^{34}$ erg s$^{-1}$ (assuming a distance of 4kpc). This source is coincident with one of the eight unidentified objects recently reported by the HESS collaboration as part of the first TeV survey of the inner part of the Galaxy. Two of these new sources found along the Galactic plane, HESS J1813-178 and HESS J1614-518, have no obvious lower energy counterpart, a fact that motivated the suggestion that they might be dark cosmic ray accelerators. HESS J1813-178 has a strongly absorbed X-ray counterpart, the ASCA source AGPS273.4-17.8, showing a power law spectrum with photon index $\sim$ 1.8 and a total (galactic plus intrinsic) absorption corresponding to N$_H$ $\sim$5 $\times$ 10$^{22}$ cm$^{-2}$. We hypothesize that the source is a pulsar wind nebula embedded in its supernova remnant. The lack of X/gamma-ray variability, the radio morphology and the ASCA spectrum are all compatible with this interpretation. In any case we rule out the hypothesis that HESS J1813-178 belongs to a new class of TeV objects or that it is a cosmic "dark particle" accelerator.