Cosmic rays and gamma radiation from the shell of SN1987A

Abstract

Detection of high-energy gamma rays from young supernovae shells1,2 can directly prove the hypothesis that the main sources of cosmic rays (CR) in our Galaxy are supernovae. This radiation is produced in nuclear collisions of accelerated protons and nuclei, through the decay of pions. On 13 April 1987 an attempt was made to measure the gamma radiation from SN1987A between 50 and 500 MeV in energy by an international team from Australia, UK, FRG and USA (R. Stauberg, personal communication). Spark chamber measurements from a balloon gave a preliminary upper limit to the flux of jγ< 3 x 10−4 cm−2 s−1. The search for high-energy gamma rays is also possible using the ground-based Cerenkov-light detectors at Potchefstroom (S. Africa) and White Cliff station (Australia) for Eγ ≳ 1 TeV, and by means of the extensive air shower (EAS) array at Buckland Park (Australia) for Eγ≳ 106 GeV. Such observations, we show here, can discover CR in the SN1987A shell if they are produced inside the shell with luminosity down to Lp ∼ 1039 erg s−1. This can support or reject a very wide class of the models of CR production by supernovae. We argue that such measurements for SN1987A will be possible during the next 1–2 years, enough time to move Cerenkov detectors from the Northern to the Southern Hemisphere.