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

Journal Article · Sat May 10 04:00:00 EDT 2014 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/786/2/145· OSTI ID:22356900

Hanabata, Y. ^[1]; Katagiri, H. ^[2]; Hewitt, J. W. ^[3]; Ballet, J. ^[4]; Fukazawa, Y. ^[5]; Fukui, Y.; Hayakawa, T. ^[6]; Lemoine-Goumard, M. ^[7]; Pedaletti, G.; Torres, D. F. ^[8]; Strong, A. W. ^[9]

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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)

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 same 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.

• OSTI ID: 22356900
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 786; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ACCELERATION
COSMIC RADIATION
DECAY
DIFFUSION
EMISSION
EXTRAPOLATION
GAMMA RADIATION
GEV RANGE
INTERACTIONS
INTERSTELLAR SPACE
SIMULATION
SPECTRA
SUPERNOVA REMNANTS
TELESCOPES
TEV RANGE