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ID 14645
file
creator
Bamba, Aya
Yamazaki, Ryo
Yoshida, Tatsuo
Terasawa, Toshio
Koyama, Katsuji
subject
acceleration of particles ISM
individual(Cassiopeia A, Kepler's Supernova Remnant G120.1+1.4, SN 1006, RCW 86)
supernova remnants
X-rays
ISM
NDC
Astronomy. Space sciences
abstract
The outer shells of young supernova remnants (SNRs) are the most plausible acceleration sites of high-energy electrons with the diffusive shock acceleration (DSA) mechanism. We studied spatial and spectral properties close to the shock fronts in four historical SNRs (Cas A, Kepler's remnant, Tycho's remnant, and RCW86) with excellent spatial resolution of Chandra. In all of the SNRs, hard X-ray emissions were found on the rims of the SNRs, which concentrate in very narrow regions ( so-called filaments); apparent scale widths on the upstreamside are below or on the order of the point-spread function of Chandra, while they are 0.'' 5 - 40 '' (0.01 - 0.4 pc) on the downstream side with most reliable distances. The spectra of these filaments can be fitted with both thermal and nonthermal ( power law and SRCUT) models. The former requires unrealistic high temperature (greater than or similar to 2 keV) and low abundances (less than or similar to 1 solar) for emission from young SNRs and may be thus unlikely. The latter reproduces the spectra with best-fit photon indices of 2.1 - 3.8, or roll-off frequencies of (0.1 28) x 10(17) Hz, which reminds us of the synchrotron emission from electrons accelerated via DSA. We consider various physical parameters as functions of the SNR age, including the previous results on SN 1006; the filament width on the downstream side increases with the SNR age, and the spectrum becomes softer, keeping a nonthermal feature. It was also found that a function, that is, the roll-off frequency divided by the square of the scale width on the downstream side, shows negative correlation with the age, which might provide us some information on the DSA theory.
journal title
Astrophysical Journal
volume
Volume 621
issue
Issue 2
start page
793
end page
802
date of issued
2005-03
publisher
University of Chicago Press
issn
0004-637X
publisher doi
language
eng
nii type
Journal Article
HU type
Journal Articles
DCMI type
text
format
application/pdf
text version
publisher
rights
Copyright (c) 2005 The American Astronomical Society
relation url
department
Graduate School of Science



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