Detection of high-energy gamma-ray emission from the globular cluster 47 tucanae with Fermi

Abstract

We report the detection of gamma-ray emissions above 200 megaelectron volts at a significance level of 17s from the globular cluster 47 Tucanae, using data obtained with the Large Area Telescope onboard the Fermi Gamma-ray Space Telescope. Globular clusters are expected to emit gamma rays because of the large populations of millisecond pulsars that they contain. The spectral shape of 47 Tucanae is consistent with gamma-ray emission from a population of millisecond pulsars. The observed gamma-ray luminosity implies an upper limit of 60 millisecond pulsars present in 47 Tucanae.