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Fermi Large Area Telescope Observations of the Supernova Remnant GS.7-0.1We present a detailed analysis of the GeV gamma-ray emission toward the supernova remnant (SNR) G8.7-0.1 with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. An investigation of the relationship among G8.7-0.l and the TeV unidentified source HESS J1804-216 provides us with an important clue on diffusion process of cosmic rays if particle acceleration operates in the SNR. The GeV gamma-ray emission is extended with most of the emission in positional coincidence with the SNR G8.7-0.l and a lesser part located outside the western boundary of G8.7-0.l. The region of the gamma-ray emission overlaps spatially-connected molecular clouds, implying a physical connection for the gamma-ray structure. The total gamma-ray spectrum measured with LAT from 200 MeV-100 GeV can be described by a broken power-law function with a break of 2.4 +/- 0.6 (stat) +/- 1.2 (sys) GeV, and photon indices of 2.10 +/- 0.06 (stat) +/- 0.10 (sys) below the break and 2.70 +/- 0.12 (stat) +/- 0.l4 (sys) above the break. Given the spatial association among the gamma rays, the radio emission of G8.7-0.1, and the molecular clouds, the decay of 1IoS produced by particles accelerated in the SNR and hitting the molecular clouds naturally explains the GeV gamma-ray spectrum. We also find that the GeV morphology is not well represented by the TeV emission from HESS J1804-216 and that the spectrum in the GeV band is not consistent with the extrapolation of the TeV gamma-ray spectrum. The spectral index of the TeV emission is consistent with the particle spectral index predicted by a theory that assumes energy-dependent diffusion of particles accelerated in an SNR. We discuss the possibility that the TeV spectrum originates from the interaction of particles accelerated in G8.7-0.1 with molecular clouds, and we constrain the diffusion coefficient of the particles.
Document ID
20110023494
Acquisition Source
Goddard Space Flight Center
Document Type
Preprint (Draft being sent to journal)
Authors
Ajello, M. (Stanford Univ. CA, United States)
Allafort, A. (Stanford Univ. CA, United States)
Baldini, L. (Istituto Nazionale di Fisica Nucleare Pisa, Italy)
Ballet, J. (Commissariat a l'Energie Atomique Gif-sur-Yvette, France)
Barbiellini, G. (Istituto Nazionale di Fisica Nucleare Trieste, Italy)
Bastieri, D. (Istituto Nazionale di Fisica Nucleare Padova, Italy)
Bechtol, K. (Stanford Univ. CA, United States)
Bellazzini, R. (Istituto Nazionale di Fisica Nucleare Pisa, Italy)
Berenji, B. (Stanford Univ. CA, United States)
Blandford, R. D. (Stanford Univ. CA, United States)
Bloom, E. D. (Stanford Univ. CA, United States)
Bonamente, E. (Istituto Nazionale di Fisica Nucleare Perugia, Italy)
Borgland, A. W. (Stanford Univ. CA, United States)
Bregeon, J. (Istituto Nazionale di Fisica Nucleare Pisa, Italy)
Brigida, M. (Bari Univ. Italy)
Bruel, P. (Centre National de la Recherche Scientifique Palaiseau, France)
Buehler, R. (Stanford Univ. CA, United States)
Buson, S. (Istituto Nazionale di Fisica Nucleare Padova, Italy)
Caliandro, G. A. (Autonoma de Barcelona Univ. Barcelona, Spain)
Cameron, R. A. (Stanford Univ. CA, United States)
Ferrara, E. C. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Harding, A. K. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Hays, E. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Moiseev, A. A. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Troja, E. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
August 25, 2013
Publication Date
January 1, 2011
Subject Category
Astronomy
Report/Patent Number
GSFC.JA.5424.2011
Distribution Limits
Public
Copyright
Public Use Permitted.

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