IGR J22517+2218 = MG3 J225155+2217: A new gamma-ray lighthouse in the distant universe

We report on the identification of a new soft gamma-ray source, namely, IGR J22517+2218, detected with INTEGRAL IBIS. The source, which has an observed 20-100 keV flux of similar to 4 x 10(-11) ergs cm(-2) s(-1), is spatially coincident with MG3 J225155+2217, a quasar at. The Swift XRT 0.5-10 keV continuum is flat (Gamma = 1.5) with evidence for a spectral curvature below 1-2 keV either due to intrinsic absorption (N-H = 3 +/- 2 x 10(22) cm(-2)) or to a change in slope (Delta Gamma = 0.5). X- ray observations indicate flux variability over a 6 day period that is further supported by a flux mismatch between Swift and INTEGRAL spectra. IGR J22517+2218 is radio-loud and has a flat radio spectrum; optically, it is a broad-line emitting quasar with the atypical property of hosting a narrow-line absorption system. The source spectral energy distribution is unusual compared to blazars of similar type: either it has the synchrotron peak in the X- ray/gamma-ray band (i.e., much higher than generally observed) or the Compton peak in the MeV range ( i.e., lower than typically measured). IGR J22517+2218=MG3 J225155+2217 is the second most distant blazar detected above 20 keV and a gamma-ray lighthouse shining from the edge of our universe.