Résumé
Some core-collapse supernovae are likely to be efficient cosmic-ray accelerators upto the PeV range,and therefore, to potentially play an important role in the overallGalactic cosmic-ray population. TheTeV gamma-ray domain can be used to study particle acceleration in the multi-TeV and PeV range. Thismotivates the study of the detectability of such supernovae by current and future gamma-rayfacilities. The gamma-ray emission of core-collapse supernovae strongly depends on the level of thetwo-photon annihilation process: high-energy gamma-ray photons emitted at the expanding shockwave following the supernova explosion can interact with soft photons from the supernovaphotosphere through the pair production channel, thereby strongly suppressing the flux of gammarays leaving the system. In the case of SN 1993J, whose photospheric and shock-related parameters arewell measured, we calculate the temporal evolution of the expected gamma-ray attenuation byaccounting for the temporal and geometrical effects. We find the attenuation to be of about 10 ordersof magnitude in the first few days after the SN explosion. The probability of detection of a supernovasimilar to SN 1993J with the Cherenkov Telescope Array is highest if observations are performed eitherearlier than 1 day, or later than 10 days after the explosion, when the gamma-ray attenuationdecreases to about 2 orders of magnitude.