Gamma-ray emission from Puppis A with Fermi-LAT telescope evidence for proton acceleration

Abstract

Supernova Remnants (SNRs) are the primary suspect among Galactic sources to accelerate particles via diffusive shock acceleration up to the necessary PeV energies.The gamma-ray emission of SNRs can provide direct evidence of leptonic (inverse Compton and bremsstrahlung) and hadronic (pion-decay from proton-proton interactions) processes. Puppis A is a middle-aged SNR interacting with interstellar clouds which has been observed in a broad energy band, from radio to gamma-rays. We analyzed its gamma-ray emission with 14 years of Fermi-LAT observations.The remnant shows a clear asymmetry in high-energy flux between East and West sides corresponding to the asymmetry found in its X-ray emission. The same asymmetry has not been found in the spectral analysis, which suggests the same origin for the gamma-ray emission in the global remnant. Moreover, we analyzed two gamma-ray sources located close to the remnant. The hardness of their spectra suggests that the gamma-ray emission can be due to particles escaping from the shock of Puppis A.