Observations of the young supernova remnant RX J1713.7-3946 with the Fermi Large Area Telescope

Abstract: We present observations of the young Supernova remnant (SNR) RX J1713.7-3946 with the Fermi Large Area Telescope (LAT). We clearly detect a source positionally coincident with the SNR. The source is extended with a best-fit extension of 0.55$^{\circ} \pm 0.04^{\circ}$ matching the size of the non-thermal X-ray and TeV gamma-ray emission from the remnant. The positional coincidence and the matching extended emission allows us to identify the LAT source with the supernova remnant RX J1713.7-3946. The spectrum of the source can be described by a very hard power-law with a photon index of $\Gamma = 1.5 \pm 0.1$ that coincides in normalization with the steeper H.E.S.S.-detected gamma-ray spectrum at higher energies. The broadband gamma-ray emission is consistent with a leptonic origin as the dominant mechanism for the gamma-ray emission.