2015A&A...577A..12F

RX J1713.7-3946 is the brightest shell-type supernova remnant (SNR) of the TeV γ-raysky. Earlier Fermi-LAT results on low energy γ-rayemission suggested that, despite large uncertainties in the background determination, the spectrum is inconsistent with a hadronic origin. We update the GeV-band spectra using improved estimates for the diffuse Galactic γ-rayemission and more than double the volume of data. We further investigate the viability of hadronic emission models for RX J1713.7-3946. We produced a high-resolution map of the diffuse Galactic γ-raybackground corrected for the HI self-absorption and used it in the analysis of more than five years worth of Fermi-LAT data. We used hydrodynamic scaling relations and a kinetic transport equation to calculate the acceleration and propagation of cosmic rays in SNR. We then determined spectra of hadronic γ-rayemission from RX J1713.7-3946, separately for the SNR interior and the cosmic-ray precursor region of the forward shock, and computed flux variations that would allow us to test the model with observations. We find that RX J1713.7-3946 is now detected by Fermi-LAT with very high statistical significance, and the source morphology is best described by that seen in the TeV band. The measured spectrum of RX J1713.7-3946 is hard with index γ=1.53±0.07, and the integral flux above 500MeV is F=(5.5±1.1)x10^–9photons/cm2/s. We demonstrate that scenarios based on hadronic emission from the cosmic-ray precursor region are acceptable for RX J1713.7-3946, and we predict a secular flux increase at a few hundred GeV at the level of around 15% over ten years, which may be detectable with the upcoming Cherenkov Telescope Array (CTA) observatory.