Fermi Large Area Telescope observations of the supernova remnant HESS J1731-347

Abstract

Context: HESS J1731-347 has been identified as one of the few TeV-bright shell-type supernova remnants (SNRs). These remnants are dominated by nonthermal emission, and the nature of TeV emission has been continuously debated for nearly a decade. Aims: We carry out the detailed modeling of the radio to gamma-ray spectrum of HESS J1731-347 to constrain the magnetic field and energetic particles sources, which we compare with those of the other TeV-bright shell-type SNRs explored before. Methods: Four years of data from Fermi Large Area Telescope (LAT) observations for regions around this remnant are analyzed, leading to no detection correlated with the source discovered in the TeV band. The Markov Chain Monte Carlo method is used to constrain parameters of one-zone models for the overall emission spectrum. Results: Based on the 99.9% upper limits of fluxes in the GeV range, one-zone hadronic models with an energetic proton spectral slope greater than 1.8 can be ruled out, which favors a leptonic origin for the gamma-ray emission, making this remnant a sibling of the brightest TeV SNR RX J1713.7-3946, the Vela Junior SNR RX J0852.0-4622, and RCW 86. The best-fit leptonic model has an electron spectral slope of 1.8 and a magnetic field of about 30 muG, which is at least a factor of 2 higher than those of RX J1713.7-3946 and RX J0852.0-4622, posing a challenge to the distance estimate and/or the energy equipartition between energetic electrons and the magnetic field of this source. A measurement of the shock speed will address this challenge and has implications on the magnetic field evolution and electron acceleration driven by shocks of SNRs.

7 pages, 3 fogures, A&A in press

References in corpus (12)

• Primary particle acceleration above 100 TeV in the shell-type Supernova Remnant RX J1713.7-3946 with deep H.E.S.S. observations
• Observations of the young supernova remnant RX J1713.7-3946 with the Fermi Large Area Telescope
• HESS VHE Gamma-Ray Sources Without Identified Counterparts
• H.E.S.S. observations of the supernova remnant RX J0852.0-4622: shell-type morphology and spectrum of a widely extended VHE gamma-ray source
• Measuring the cosmic ray acceleration efficiency of a supernova remnant
• Inverse Compton Emission from Galactic Supernova Remnants: Effect of the Interstellar Radiation Field
• In which shell-type SNRs should we look for gamma-rays and neutrinos from p-p collisions?
• Discovery of the radio and X-ray counterpart of TeV Gamma-ray source HESS J1731-347
• The Slow X-Ray Expansion of the Northwestern Rim of the Supernova Remnant RX J0852.0-4622
• Unified model for the gamma-ray emission of supernova remnants
• Modeling the Multi-Wavelength Emission of Shell-Type Supernova Remnant RX J1713.7-3946
• Stochastic Electron Acceleration in Shell-Type Supernova Remnants II

Cited by in corpus (7)

• Probing The Local Environment of the Supernova Remnant HESS J1731-347 with CO and CS Observations
• Detection of GeV $\gamma$-ray emission in the direction of HESS J1731-347 with Fermi-LAT
• XMM-Newton observations of the non-thermal supernova remnant HESS J1731-347 (G353.6-0.7)
• Evolution of High-Energy Particle Distribution in Mature Shell-Type Supernova Remnants
• A Systematic Study of the Thermal and Nonthermal Emission in the Supernova Remnant RCW 86 with Suzaku
• The structure of TeV-bright shell-type supernova remnants
• Detection of the extended $\gamma$-ray emission from the high Galactic latitude Calvera's SNR candidate