Analysis of GeV-bandγ-ray emission from supernova remnant RX J1713.7-3946

Abstract

Context. RX J1713.7-3946 is the brightest shell-type supernova remnant (SNR) of the TeV γ-ray sky. Earlier Fermi-LAT results on low energy γ-ray emission suggested that, despite large uncertainties in the background determination, the spectrum is inconsistent with a hadronic origin. Aims. We update the GeV-band spectra using improved estimates for the diffuse Galactic γ-ray emission and more than double the volume of data. We further investigate the viability of hadronic emission models for RX J1713.7-3946. Methods. We produced a high-resolution map of the diffuse Galactic γ-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 γ-ray emission 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. Results. 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 500 MeV is F = (5.5 ± 1.1) × 10 −9 photons cm −2 s −1 . We demonstrate that scenarios based on hadronic emission from the cosmic-ray precursor region are acceptable for RX J1713.7-3946, 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.

Post-adiabatic supernova remnants in an interstellar magnetic field: oblique shocks and non-uniform environment

“…There are three scenarii for the hadronic γ-rays from SNR-MC complexes. A gamma-ray emission from clouds near SNRs can arise if the shock-accelerated protons diffuse towards an adjacent but physically separated cloud (Gabici & Aharonian 2007;Gabici et al 2009;Telezhinsky et al 2012;Federici et al 2015). One can also envision that the shock moves in a medium which is uniform on large scales but harboring small dense cloudlets and it re-accelerates preexisting cosmic rays (e.g.…”

Evolution of High-Energy Particle Distribution in Mature Shell-Type Supernova Remnants

“…Only recently, very weak thermal X-ray emission has been detected from the inner region of the remnant (Katsuda et al 2015). The spectra observed in radio, X-ray, GeV, and TeV bands, which are shown in Figure 1, are obtained from Acero et al (2009), Tanaka et al (2008), Federici et al (2015, and Aharonian et al (2011), respectively. The nature of its γ-ray emission is still being debated Federici et al 2015).…”

Detection of Two TeV Shell-type Remnants at GeV Energies with FERMI LAT: HESS J1731-347 and SN 1006

“…We need to study all these SNRs at GeV energies to characterize the shape of the spectrum in a wide energy range and be able to identify the mechanism of γ-ray production. Among the five TeV shelltype remnants, three have already been detected and carefully studied at GeV energies: RX J0852.0−4622 (Tanaka et al 2011), RX J1713.7−3946 (Abdo et al 2011Federici et al 2015) and RCW 86 (Ajello et al 2016). However, HESS J1731−347 and SN 1006 remained undetected, though a recent work reported first evidence of γ-ray emission coming from the latter with ∼ 4σ significance (Xing et al 2016).…”