PoS - Proceedings of Science
Volume 395 - 37th International Cosmic Ray Conference (ICRC2021) - GAI - Gamma Ray Indirect
Modelling uncertainties in GeV - TeV flux predictions of Galactic globular clusters
C. Venter*, H. Davids, A. Kopp and M. Backes
Full text: pdf
Pre-published on: July 08, 2021
Published on: March 18, 2022
Globular clusters are multi-band emitters, with their gamma-ray emission having been variously attributed to dark matter annihilation, a resident gamma-ray burst, or collective emission from a white-dwarf or millisecond-pulsar population hosted by the cluster. Terzan 5 has plausibly been detected in the gamma-ray band by H.E.S.S., which also produced constraining stacking
upper limits on the integral gamma-ray fluxes of a population of other Galactic globular clusters. Using a leptonic model that invokes host millisecond pulsars in globular clusters as sources of relativistic particles, we perform three case studies. First, we demonstrate that uncertainty in model parameters leads to a large spread in the predicted gamma-ray flux for a population of clusters, yet there are regions in parameter space for which the stringent H.E.S.S. stacking upper limits are satisfied. Two additional case studies on M15 (for which MAGIC recently derived stringent differential flux upper limits) and 𝜔 Cen (from which five pulsars have recently been detected at radio frequencies) indicate that it is vital to increase measurement accuracy on key model parameters to improve precision in predictions of cluster fluxes. This has important implications for the observational strategy of the CTA.
DOI: https://doi.org/10.22323/1.395.0927
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