High spectral resolution gamma ray astronomy in the energy region 50keV to l0MeV

Abstract

Observations of the Crab nebula region and of the unusual active galaxy NGC1275 made during a balloon flight of the Durham high spectral resolution gamma ray telescope are described. From the Crab, spectral line fluxes were detected at 79 keV (transient), 405 keV, and at 1050 keV. The first two are possible confirmation of previous results. From NGC1275, evidence of two-photon electron-positron annihilation radiation with the expected redshifted energy of 502 keV was observed. Possible interpretations are suggested.