Identifying the brightest Galactic globular clusters for future observations by H.E.S.S. and CTA
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Date
2018Author
Ndiyavala, Hambeleleni
Krüger, Petrus Paulus
Venter, Christo
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We present results from an emission code that assumes millisecond pulsars to be sources
of relativistic particles in globular clusters (GCs) and models the resulting spectral energy
distribution of Galactic GCs due to these particles’ interaction with the cluster magnetic and
soft-photon fields.We solve a transport equation for leptons and calculate inverse Compton and
synchrotron radiation tomake predictions for the flux expected fromGalactic GCs.We perform
a parameter study and also constrain model parameters for three GCs using γ -ray and X-ray
data. We next study the detectability of 16 Galactic GCs for the High Energy Stereoscopic
System (H.E.S.S.) and the Cherenkov Telescope Array (CTA), ranking them according to their
predicted TeV flux. The spectrum of each cluster and therefore the detectability ranking is very
sensitive to the choice of parameters.We expect H.E.S.S. to detect two more GCs (in addition
to Terzan 5), i.e. 47 Tucanae and NGC 6388, if these clusters are observed for 100 h. The five
most promising GCs for CTA are NGC 6388, 47 Tucanae, Terzan 5, Djorg 2 and Terzan 10.We
lastly expect CTA to detect more than half of the known Galactic GC population, depending
on observation time and model parameters
URI
http://hdl.handle.net/10394/26239https://doi.org/10.1093/mnras/stx2336
https://academic.oup.com/mnras/article-pdf/473/1/897/21383598/stx2336.pdf