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Title: Detailed investigation of the gamma-ray emission in the vicinity of SNR W28 with Fermi-LAT

We present a detailed investigation of the γ-ray emission in the vicinity of the supernova remnant (SNR) W28 (G6.4–0.1) observed by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. We detected significant γ-ray emission spatially coincident with TeV sources HESS J1800–240A, B, and C, located outside the radio boundary of the SNR. Their spectra in the 2-100 GeV band are consistent with the extrapolation of the power-law spectra of the TeV sources. We also identified a new source of GeV emission, dubbed Source W, which lies outside the boundary of TeV sources and coincides with radio emission from the western part of W28. All of the GeV γ-ray sources overlap with molecular clouds in the velocity range from 0 to 20 km s{sup –1}. Under the assumption that the γ-ray emission toward HESS J1800–240A, B, and C comes from π{sup 0} decay due to the interaction between the molecular clouds and cosmic rays (CRs) escaping from W28, they can be naturally explained by a single model in which the CR diffusion coefficient is smaller than the theoretical expectation in the interstellar space. The total energy of the CRs escaping from W28 is constrained through the samemore » modeling to be larger than ∼2 × 10{sup 49} erg. The emission from Source W can also be explained with the same CR escape scenario.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ; ;  [6] ;  [7] ; ;  [8] ;  [9] ;  [10]
  1. Institute for Cosmic-Ray Research, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8582 (Japan)
  2. College of Science, Ibaraki University, 2-1-1, Bunkyo, Mito 310-8512 (Japan)
  3. CRESST, University of Maryland, Baltimore County, Baltimore, MD 21250 (United States)
  4. Laboratoire AIM, CEA-IRFU/CNRS/Université Paris Diderot, Service d'Astrophysique, CEA Saclay, F-91191 Gif sur Yvette (France)
  5. Department of Physical Sciences, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526 (Japan)
  6. Department of Physics and Astrophysics, Nagoya University, Chikusa-ku Nagoya 464-8602 (Japan)
  7. Centre d'Études Nucléaires de Bordeaux Gradignan, IN2P3/CNRS, Université Bordeaux 1, BP120, F-33175 Gradignan Cedex (France)
  8. Institut de Ciències de l'Espai (IEEE-CSIC), Campus UAB, 08193 Barcelona (Spain)
  9. Max-Planck Institut für extraterrestrische Physik, D-85748 Garching (Germany)
  10. Department of Physics and Mathematics, Aoyama Gakuin University, Sagamihara, Kanagawa 252-5258 (Japan)
Publication Date:
OSTI Identifier:
22356900
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 786; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCELERATION; COSMIC RADIATION; DECAY; DIFFUSION; EMISSION; EXTRAPOLATION; GAMMA RADIATION; GEV RANGE; INTERACTIONS; INTERSTELLAR SPACE; SIMULATION; SPECTRA; SUPERNOVA REMNANTS; TELESCOPES; TEV RANGE