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arXiv · 1002.2431

Fermi Discovery of Gamma-ray Emission from the Globular Cluster Terzan 5

A. K. H. Kong·C. Y. Hui·K. S. Cheng
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Abstract

We report the discovery of gamma-ray emission from the Galactic globular cluster Terzan 5 using data taken with the Fermi Gamma-ray Space Telescope, from 2008 August 8 to 2010 January 1. Terzan 5 is clearly detected in the 0.5-20 GeV band by Fermi at ~27σlevel. This makes Terzan 5 as the second gamma-ray emitting globular cluster seen by Fermi after 47 Tuc. The energy spectrum of Terzan 5 is best represented by an exponential cutoff power-law model, with a photon index of ~1.9 and a cutoff energy at ~3.8 GeV. By comparing to 47 Tuc, we suggest that the observed gamma-ray emission is associated with millisecond pulsars, and is either from the magnetospheres or inverse Compton scattering between the relativistic electrons/positrons in the pulsar winds and the background soft photons from the Galactic plane. Furthermore, it is suggestive that the distance to Terzan 5 is less than 10 kpc and > 10 GeV photons can be seen in the future.

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A. K. H. Kong, C. Y. Hui, K. S. Cheng. 2010-02-11. Fermi Discovery of Gamma-ray Emission from the Globular Cluster Terzan 5. https://doi.org/10.1088/2041-8205%2F712%2F1%2Fl36

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