[en] Cosmic ray interactions can be investigated indirectly in γ ray astronomy, with the observation of spectral and morphological features of certain classes of sources. MAGIC is a stereoscopic system of two γ ray telescopes, located at La Palma (Canaries), with access to the energy window between 50 GeV and 30 TeV. Sources of high relevance for the study of very high energy hadronic interactions are active galactic nuclei, as blazars and radio galaxies. MAGIC has detected about fifty such extragalactic objects; we will present some where the emission is explained with accelerated hadrons in interaction with ambient photons. We will also mention cosmic ray acceleration in galaxy clusters. Other than that, hadron-hadron interactions are supposed to take place in some supernova remnants in interaction with surrounding molecular clouds; we will show some results, in connection with cosmic rays of galactic origin. Finally, about other possible components, we will mention the measurement of the diffuse electron and positron spectrum. Trustingly, the close connection between particle physics and astrophysics will contribute in future years to many new interesting observations. (authors)

[en] Supernova remnants are a probable site of acceleration of particles via diffusive shock processes. High energies carried by electrons or protons are radiated into photons detectable from radio to γ rays. MAGIC has recently observed W51C, one of the most luminous galactic supernova remnants, and completed its spectrum between 50 GeV and 5 TeV. We modelled different processes for high energy photon emission of this source, and compared the predictions with the measured spectral energy distribution. It is plausible that hadrons are accelerated in the expansion front of this source, in interaction with the surrounding molecular cloud, and photons are produced in the decay of neutral mesons created in hadronic collisions.