Molecular Clouds as a Probe of Cosmic-Ray Acceleration in a Supernova Remnant

We study cosmic-ray acceleration in a supernova remnant (SNR) and the escape from it. We model nonthermal particle and photon spectra for the hidden SNR in the open cluster Westerlund 2, and the old-age mixed-morphology SNR W 28. We assume that the SNR shock propagates in a low-density cavity, which...

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Bibliographic Details
Published in:Astrophysical journal. Letters 2009-12, Vol.707 (2), p.L179-L183
Main Authors: Fujita, Yutaka, Ohira, Yutaka, Tanaka, Shuta J, Takahara, Fumio
Format: Article
Language:English
Subjects:
ACCELERATION
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
BOSONS
COSMIC RADIATION
COSMIC RADIO SOURCES
ELEMENTARY PARTICLES
ENERGY DEPENDENCE
EXPLOSIONS
GAMMA SPECTRA
IONIZING RADIATIONS
MASSLESS PARTICLES
MORPHOLOGY
PARTICLES
PHOTONS
RADIATIONS
SPECTRA
STARS
SUPERNOVA REMNANTS
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Summary:We study cosmic-ray acceleration in a supernova remnant (SNR) and the escape from it. We model nonthermal particle and photon spectra for the hidden SNR in the open cluster Westerlund 2, and the old-age mixed-morphology SNR W 28. We assume that the SNR shock propagates in a low-density cavity, which is created and heated through the activities of the progenitor stars and/or previous supernova explosions. We indicate that the diffusion coefficient for cosmic rays around the SNRs is less than ~1% of that away from them. We compare our predictions with the gamma-ray spectra of molecular clouds illuminated by the cosmic rays (Fermi and H.E.S.S.). We found that the spectral indices of the particles are ~2.3. This may be because the particles were accelerated at the end of the Sedov phase, and because energy-dependent escape and propagation of particles did not much affect the spectrum.
ISSN:1538-4357
0004-637X
2041-8205
1538-4357
DOI:10.1088/0004-637X/707/2/L179