NBIA Seminar: Silvia Celli

Since its discovery more than hundred years ago, the origin of the cosmic-ray flux measured on Earth is still unknown. In order to explain the energy region below the knee, at few PeV, supernova remnants (SNRs) are usually addressed as main cosmic accelerators. So far, no clear indication of PeV energies has been observed in such a kind of sources: in fact, even the brightest TeV SNR, namely RX J1713.7-3946, shows a spectrum with a cut-off at gamma-ray energies of few TeVs. However, such non-observations do not prevent SNRs to have acted as PeVatrons in the past. Indeed, the highest energy particles are expected to escape the SNR shock at the end of the free expansion stage, eventually propagating in the surrounding interstellar medium. The interaction of these particles with massive clouds located in our Galaxy would give rise to very-high-energy gamma rays and neutrinos, which would then propagate almost unaffected towards Earth. I will discuss the physics of such processes, in the context of the acceleration, escape and propagation of high-energy particles in SNRs, highlighting related radiative observations.