Search for γ rays from the supernova 1987A at energies greater than 100 TeV

We searched for ultrahigh-energy γ rays emitted by the supernova 1987A with a new cosmic-ray facility installed at the Black Birch Range in New Zealand. The observations from 13 October to 3 December 1987 suggest no clear clustering of events around the direction of the supernova. We conclude that an upper limit on the flux γ rays of energies greater than 100 TeV is 1.1×${10}^{\mathrm{-}12}$ ${\mathrm{cm}}^{\mathrm{-}2}$ ${\mathrm{s}}^{\mathrm{-}1}$ (95% confidence limit) for a differential spectral index α=2.0 and source distance d=50 kpc. This value gives an upper bound on the γ-ray luminosity of the supernova of 5.5×${10}^{38}$ erg ${\mathrm{s}}^{\mathrm{-}1}$ for ${10}^{14}$–${10}^{17}$ eV.