Evidence for the detection of gamma rays from Centaurus A at gamma-ray energies above 300 GeV

Abstract

Results of extended observations of the active galaxy NGC 5128 (Cen A) at energies above 100 GeV are presented. Data were recorded from three observing periods (1972-1974) in Australia. The atmospheric Cerenkov technique was used, together with partial cosmic-ray rejection, to search for gamma-ray-initiated extensive air showers from the direction of Cen A. A 4.5 sigma (time-averaged) excess over background was detected. Some implications of this probable gamma-ray flux are discussed.