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

Abstract

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.

Authors:
 [1];  [2]
  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)
Publication Date:
OSTI Identifier:
21305093
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal Letters
Additional Journal Information:
Journal Volume: 712; Journal Issue: 1; Other Information: DOI: 10.1088/2041-8205/712/1/L36; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 2041-8205
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; 99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE; COMPTON EFFECT; ELECTRONS; ENERGY SPECTRA; GAMMA RADIATION; PHOTONS; POSITRONS; PULSARS; RELATIVISTIC RANGE; STARS; TELESCOPES

Citation Formats

Kong, A K. H., Hui, C Y, and Cheng, K. S. FERMI DISCOVERY OF GAMMA-RAY EMISSION FROM THE GLOBULAR CLUSTER TERZAN 5. United States: N. p., 2010. Web. doi:10.1088/2041-8205/712/1/L36; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA).
Kong, A K. H., Hui, C Y, & Cheng, K. S. FERMI DISCOVERY OF GAMMA-RAY EMISSION FROM THE GLOBULAR CLUSTER TERZAN 5. United States. doi:10.1088/2041-8205/712/1/L36; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA).
Kong, A K. H., Hui, C Y, and Cheng, K. S. Sat . "FERMI DISCOVERY OF GAMMA-RAY EMISSION FROM THE GLOBULAR CLUSTER TERZAN 5". United States. doi:10.1088/2041-8205/712/1/L36; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA).
@article{osti_21305093,
title = {FERMI DISCOVERY OF GAMMA-RAY EMISSION FROM THE GLOBULAR CLUSTER TERZAN 5},
author = {Kong, A K. H. and Hui, C Y and Cheng, K. S.},
abstractNote = {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.},
doi = {10.1088/2041-8205/712/1/L36; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)},
journal = {Astrophysical Journal Letters},
issn = {2041-8205},
number = 1,
volume = 712,
place = {United States},
year = {2010},
month = {3}
}