FERMI DISCOVERY OF GAMMA-RAY EMISSION FROM THE GLOBULAR CLUSTER TERZAN 5

Journal Article · Sat Mar 20 04:00:00 EDT 2010 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/712/1/L36; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)· OSTI ID:21305093

Kong, A K. H. ^[1]; Hui, C Y ^[2]

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1. Institute of Astronomy and Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan (China)
2. Department of Astronomy and Space Science, Chungnam National University, Daejeon (Korea, Republic of)

We report the discovery of gamma-ray emission from the Galactic globular cluster (GC) 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 {approx}27{sigma} level. This makes Terzan 5 the second gamma-ray-emitting GC 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 {approx}1.9 and a cutoff energy at {approx}3.8 GeV. By comparing Terzan 5 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.

• OSTI ID: 21305093
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 1 Vol. 712; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
99 GENERAL AND MISCELLANEOUS
COMPTON EFFECT
ELECTRONS
ENERGY SPECTRA
GAMMA RADIATION
PHOTONS
POSITRONS
PULSARS
RELATIVISTIC RANGE
STARS
TELESCOPES