The First Measurement of Cassiopeia A’s Forward Shock Expansion Rate
نویسندگان
چکیده
منابع مشابه
The First Measurement of Cassiopeia A’s Forward Shock Expansion Rate
We have obtained a second epoch observation of the Cassiopeia A supernova remnant (SNR) with the Chandra X-ray Observatory to measure detailed X-ray proper motions for the first time. Both epoch observations are 50 ks exposures of the ACIS-S3 chip and they are separated by 2 years. Measurements of the thin Xray continuum dominated filaments located around the edge of the remnant (that are ident...
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We have for the first time measured the overall expansion rate of the supernova remnant Cas A as seen in Xrays using ROSAT and Einstein HRI images with time differences up to almost 17 years. The overall expansion timescale of Cas A is found to be 501±15 yr. This is significantly shorter than the timescale based on high resolution radio data. Although the results clearly indicate that Cas A is ...
متن کاملThe expansion of Cassiopeia A as seen in X-rays
We have for the first time measured the overall expansion rate of the supernova remnant Cas A as seen in X-rays using ROSAT and Einstein HRI images with time differences up to almost 17 years. The overall expansion timescale of Cas A is found to be 501 ± 15 yr. This is significantly shorter than the timescale based on high resolution radio data. Although the results clearly indicate that Cas A ...
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We present the first X-ray expansion measurement of the SNR Cas A. We compared new ROSAT to archived Einstein HRI images with a separation of 17 years. The remnant is seen to be expanding, on average, at a rate of 0.20± 0.01 % yr−1, which is twice as fast as the expansion of the bright radio ring and two-thirds as fast as the ensemble of optical Fast Moving Knots. This argues that we are observ...
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We study the entropy rate of a hidden Markov process, defined by observing the output of a symmetric channel whose input is a first order Markov process. Although this definition is very simple, obtaining the exact amount of entropy rate in calculation is an open problem. We introduce some probability matrices based on Markov chain's and channel's parameters. Then, we try to obtain an estimate ...
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ژورنال
عنوان ژورنال: The Astrophysical Journal
سال: 2003
ISSN: 0004-637X,1538-4357
DOI: 10.1086/374813