Fermilarge Area Telescope Observation of Supernova Remnant S147

We present an analysis of gamma-ray data obtained with the Large Area Telescope on board the Fermi Gamma-ray Space Telescope in the region around supernova remnant (SNR) S147 (G180.0−1.7). A spatially extended gamma-ray source detected in an energy range of 0.2–10 GeV is found to coincide with SNR S147. We confirm its spatial extension at >5σ confidence level. The gamma-ray flux is (3.8 ± 0.6) × 10 −8 photons cm −2 s −1 , corresponding to a luminosity of 1.3 × 10 34 ( d /1.3 kpc) 2 erg s −1 in this energy range. The gamma-ray emission exhibits a possible spatial correlation with the prominent Hα filaments of SNR S147. There is no indication that the gamma-ray emission comes from the associated pulsar PSR J0538+2817. The gamma-ray spectrum integrated over the remnant is likely dominated by the decay of neutral π mesons produced through the proton–proton collisions in the filaments. The reacceleration of the pre-existing cosmic rays and subsequent adiabatic compression in the filaments is sufficient to provide the energy density required of high-energy protons.