2FHL J0826.1-4500: Discovery of a Possible Shock-Cloud Interaction on the Western Edge of the Vela Supernova Remnant

Abstract

We report on the investigation of a very high-energy, Galactic γ-ray source recently discovered at >50 GeV using the Large Area Telescope on board Fermi. This object, 2FHL J0826.1-4500, displays one of the hardest >50 GeV spectra (photon index Γ _γ ∼ 1.6) in the 2FHL catalog, and a follow-up observation with XMM-Newton has uncovered diffuse, soft thermal emission at the position of the γ-ray source. A detailed analysis of the available multi-wavelength data shows that this source is located on the western edge of the Vela supernova remnant (SNR): the observations and the modeling of the spectral energy distribution support a scenario where this γ-ray source is the byproduct of the interaction between the SNR shock and a neutral hydrogen cloud. If confirmed, this shock-cloud interaction would make 2FHL J0826.1-4500 a promising candidate for efficient particle acceleration.