ICRC2015

Analysis of GeV-band gamma-ray emission from SNR RX J1713.7-3946

30 Jul 2015, 15:30

1h

Mississippi Foyer (World Forum)

Board: 129

Poster contribution GA-TH Poster 1 GA

Speaker

Robert Brose (DESY)

Description

RX J1713-3946 is the brightest shell-type supernova remnant (SNR) of the TeV gamma-ray sky. Earlier Fermi-LAT results on low energy gamma-ray emission 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 gamma-ray emission and more than double the volume of data. We further investigate the viability of hadronic emission models for RX J1713-3946. We produced a high-resolution map of the diffuse Galactic gamma-ray background 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 gamma-ray emission from RX J1713-3946, 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 J1713-3946 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 J1713-3946 is hard with index $\gamma=1.53\pm0.07$, and the integral flux above 500 MeV is $F = (5.5\pm1.1)\times10^{-9}$ photons cm$^{-2}$ s$^{-1}$. We demonstrate that scenarios based on hadronic emission from the cosmic-ray precursor region are acceptable for RX J1713-3946, 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.