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arXiv · 1012.0243

A Decline in the Nonthermal X-ray Emission from Cassiopeia A

Daniel J. Patnaude·Jacco Vink·J. Martin Laming·Robert A. Fesen
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Abstract

We present new Chandra ACIS-S3 observations of Cassiopeia A which, when combined with earlier ACIS-S3 observations, show evidence for a steady ~ 1.5-2%/yr decline in the 4.2-6.0 keV X-ray emission between the years 2000 and 2010. The computed flux from exposure corrected images over the entire remnant showed a 17% decline over the entire remnant and a slightly larger (21%) decline from regions along the remnant's western limb. Spectral fits of the 4.2-6.0 keV emission across the entire remnant, forward shock filaments, and interior filaments indicate the remnant's nonthermal spectral powerlaw index has steepened by about 10%, with interior filaments having steeper powerlaw indices. Since TeV electrons, which give rise to the observed X-ray synchrotron emission, are associated with the exponential cutoff portion of the electron distribution function, we have related our results to a change in the cutoff energy and conclude that the observed decline and steepening of the nonthermal X-ray emission is consistent with a deceleration of the remnant's ~5000 km/s forward shock of ~10--40 km/s/yr

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Daniel J. Patnaude, Jacco Vink, J. Martin Laming, Robert A. Fesen. 2010-12-01. A Decline in the Nonthermal X-ray Emission from Cassiopeia A. https://doi.org/10.1088/2041-8205%2F729%2F2%2Fl28

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