Investigating gamma-ray fluxes from globular clusters

Abstract

Globular clusters are large collections of old stars that are orbiting the core of a galaxy. Our Milky Way Galaxy has about 160 known clusters, with perhaps more to be discovered. We first accumulated the necessary parameters for 16 clusters and ran a numerical model that predicts the inverse Compton gamma-ray flux expected from each cluster. We also reanalysed data from 16 clusters observed by the H.E.S.S. very-high-energy (> 100 GeV) gamma-ray telescopes. We confirmed the detection of Terzan 5 and found flux upper limits for the remaining 15 sources that were consistent with published results. We attempted to constrain some source parameters using X-ray and gamma-ray data. We lastly list the five most promising clusters for future observations by the Cherenkov Telescope Array.