There are only a few PeVatron candidates known in our Galaxy which might contribute particles up to the knee of the cosmic-ray spectrum.
HESS J1641.0-4619, a gamma-ray source located in the Galactic plane and detected by H.E.S.S. above 4 TeV, is one of them.
Characterized as a point source with a hard spectral index, HESS J1641.0-4619 remains unidentified but is coincident with a radio SNR G338.5+0.1 and the dense HII region G338.4+0.0.
With an angular extent of only 0.25°, the high energy gamma-ray source HESS J1640.6-4633, coincident with the composite SNR 338.3-0.0 and the pulsar PSR J1640-4631, was originally classified as an extremely powerful SNR. In this context, the escape of cosmic-ray protons accelerated by G338.3-0.0 colliding with the ambient dense gas would be able to produce the emission of HESS J1641.0-619,
providing a self-consistent explanation for the gamma-ray emission of both sources.
Using 9 years of Fermi LAT pass 8 data, we analyzed these two sources from 100 MeV to 800 GeV. Our extensive morphological and spectral analyses provide new constraints on the origin of the gamma-ray emission as well as the efficiency of these two H.E.S.S. sources to accelerate protons and contribute to the galactic cosmic-ray flux around the knee.