Fermi Gamma-ray Space Telescope

Gamma-ray emission from globular clusters: more than just millisecond pulsars?

Anthony Brown
(Celine Boehm, Paula Chadwick, Thomas Lacroix, Sheridan Lloyd)


Early in its mission, the Fermi-LAT detector discovered the globular cluster 47 Tuc to be gamma-ray bright, with the observed gamma-ray flux being attributed to a population of unresolved millisecond pulsars. Over the last 10 years since this discovery, the list of known gamma-ray bright globular clusters has grown, and the advent of the PASS 8 data has allowed us study the spectral properties of these globular clusters with unparalleled accuracy and sensitivity. In this talk we present the results of our investigation of the brightest gamma-ray emitting globular clusters, and discuss the growing evidence that the gamma-ray emission is due to an ensemble of source types, rather than just unresolved millisecond pulsars.