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 bremsstrahlung^2–6. 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.