Fermi Gamma-ray Space Telescope

Broadband Spectral Modeling of the Galactic Globular Cluster Terzan 5

Hambeleleni Ndiyavala
(H. NDIYAVALA, C. VENTER, T. J. JOHNSON, A. K. HARDING on behalf of the Fermi LAT Collaboration; S. CASANOVA, A.-C. CLAPSON, W. DOMAINKO, M. DYRDA, P. EGER, M. JAMROZY, A. KOPP, and D. J. VAN DER WALT)

Abstract:

Terzan 5 is the only Galactic globular cluster plausibly detected at very high energies (E > 100 GeV) by the High Energy Stereoscopic System (H.E.S.S.) and has an unexpected, asymmetric morphology offset from the cluster center. We present new continuum radio data from Effelsberg Radio Telescope and the Fermi Large Area Telescope on this source. Our fit to the broadband spectral energy distribution assumes that emission originates from a population of embedded millisecond pulsars and their leptonic winds. Our model invokes unpulsed synchrotron and inverse Compton components to model radio and TeV data, cumulative pulsed curvature radiation to fit the Fermi data, and cumulative synchrotron emission by electron-positron pairs within the pulsar magnetospheres to explain the hard Chandra X-ray spectrum. While our model provides reasonable spectral fits, more and higher-quality spectral and spatial data will help discriminate between competing proposed scenarios for the broadband emission, such as a hadronic (short gamma-ray burst remnant) or white-dwarf origin thereof.