SIMBAD references

Globular clusters are a source of γ-ray radiation. AtGeV energies, their emission is attributed to magnetospheric activity of millisecond pulsars residing in the clusters. Inverse Compton scattering (ICS) of ambient photon fields on relativistic particles diffusing through cluster environment is thought to be the source ofGeV to TeV emission of globular clusters. Using pair starved polar cap model, γ-ray emission from synthetic millisecond pulsar was modelled. In addition to pulsar emission characteristics, the synthetic pulsar model yielded spectra of electrons escaping pulsar magnetosphere. To simulate γ-ray emission of globular cluster, both products of synthetic millisecond pulsar modelling were used. γ-ray spectra of synthetic millisecond pulsars residing in the cluster were summed to produce the magnetospheric component of cluster emission. Electrons ejected by these pulsars were injected into synthetic globular cluster environment. Their diffusion and interaction, both, with cluster magnetic field and ambient photon fields, were performed with Bednarek and Sitarek model yielding ICS component of cluster emission. The sum of the magnetospheric and ICS components gives the synthetic γ-ray spectrum of globular cluster. The synthetic cluster spectrum stretches fromGeV to TeV energies. Detailed modelling was performed for two globular clusters: Terzan 5 and 47 Tucanae. Simulations are able to reproduce (within errors) the shape and the flux level of theGeV part of the spectrum observed for both clusters with the Fermi/Large Area Telescope instrument. The synthetic flux level obtained in the TeV part of the clusters' spectrum is in agreement with an High Energy Stereoscopic System (HESS) upper limit determined for 47 Tucanae, and with emission level recently detected for Terzan 5 with HESS telescope. The synthetic globular cluster model, however, is not able to reproduce the exact shape of the TeV spectrum observed for Terzan 5.