HESS and Fermi-LAT discovery of gamma-rays from the blazar 1ES 1312-423

A deep observation campaign carried out by the High Energy Stereoscopic System (HESS) on Centaurus A enabled the discovery of γ -rays from the blazar 1ES 1312 − 423, 2 ◦ away from the radio galaxy. With a differential flux at 1 TeV of φ (1 TeV) = (1.9 ± 0.6 stat ± 0.4 sys ) × 10 − 13 cm − 2 s − 1 TeV − 1 corresponding to 0.5 per cent of the Crab nebula differential flux and a spectral index (cid:5) = 2.9 ± 0.5 stat ± 0.2 sys , 1ES 1312 − 423 is one of the faintest sources ever detected in the very high energy ( E > 100 GeV) extragalactic sky. A careful analysis using three and a half years of Fermi Large Area Telescope ( Fermi -LAT) data allows the discovery at high energies (E > 100 MeV) of a hard spectrum ( (cid:5) = 1.4 ± 0.4 stat ± 0.2 sys ) source coincident with 1ES 1312 − 423. Radio, optical, UV and X-ray observations complete the spectral energy distribution of this blazar, now covering 16 decades in energy. The emission is successfully fitted with a synchrotron self-Compton model for the non-thermal component, combined with a blackbody spectrum for the optical emission from the host galaxy.