Physical Sciences: Two New Point Sources of High Energy Cosmic Gamma Rays

Abstract

MORRISON1 was the first to suggest that certain astronomical objects might emit a measurable flux of γ-rays. By the middle of the last decade much theoretical work had been done on the flux to be expected from neutral pion decay, inverse Compton collisions and bremsstrahlung2–6. Evidence for the detection of such a point source of cosmic γ-rays above 50 MeV, Sgr γ-1, was reported by the CWRU–Melbourne collaboration7 and Fazio8 reviewed high energy γ-ray astronomy in early 1970, but as far as we know, no other observation of this source has been made at γ-ray, X-ray or longer wavelengths. The identification of Sgr γ-1 was based on preliminary analysis of spark chamber data from two high altitude flights in Australia and a third flight has confirmed this source. The combined data from the three flights make possible the identification of two other point sources of high energy γ-rays which agree in position with known hard X-ray sources. We find no evidence on any flight for a diffuse line source along the galactic plane.