100 TeV Gamma-Ray Observation of the Crab Nebula with the Tibet Air Shower Array
2019 July 22
The Tibet air shower (AS) array and underground water-Cherenkov-type muon detector (MD) array have been successfully operated since 2014, at an altitude of 4,300 m in Tibet, China. we observed 24 gamma-ray events with energy greater than 100 TeV against 5.5 background events, which corresponds to 5.6$\sigma$ statistical significance (Amenomori et al. 2019). The highest energy of the detected gamma rays is estimated to be 450 TeV. This is the first detection of gamma rays beyond 100 TeV from an astrophysical source, and a pioneering work opening a new higher energy window in the astronomy and astrophysics.