Fast Variability of Nonthermal X-Ray Emission in Cassiopeia A: Probing Electron Acceleration in Reverse-Shocked Ejecta
Fast Variability of Nonthermal X-Ray Emission in Cassiopeia A: Probing Electron Acceleration in Reverse-Shocked Ejecta
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DOI：
10.1086/588190
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发表时间：
2008-03
期刊：
影响因子：
--
通讯作者：
Y. Uchiyama;F. Aharonian
中科院分区：
文献类型：
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作者：
Y. Uchiyama;F. Aharonian
最近发现的超新星遗迹（SNR）RX J1713.7-3946的同步加速器X射线发射的年尺度变化，启动了我们的研究多历元的X射线图像和光谱的年轻SNR仙后座A的基础上，在2000年，2002年和2004年采取的钱德拉档案数据。我们已经发现了一些与反向冲击区有关的X射线丝或结的X射线强度的年尺度时间变化。变化的灯丝的X射线光谱的特征在于由一个无特征的连续，并与光子指数在1.9-2.3的幂律描述。铁K线等效宽度的上限为110 eV，这有利于X射线发射的同步加速器起源。4年的特征变化时间尺度可以解释的影响，快速同步加速器冷却和扩散冲击加速度与一个合理的磁场为1 mG。X射线变率为研究超新星冲击波中的粒子加速提供了一种新的有效途径。
Recent discovery of the year-scale variability in the synchrotron X-ray emission of the supernova remnant (SNR) RX J1713.7–3946 has initiated our study of multiepoch X-ray images and spectra of the young SNR Cassiopeia A based on the Chandra archive data taken in 2000, 2002, and 2004. We have found year-scale time variations in the X-ray intensity for a number of X-ray filaments or knots associated with the reverse-shocked regions. The X-ray spectra of the variable filaments are characterized by a featureless continuum, and described by a power law with a photon index within 1.9-2.3. The upper limits on the iron K-line equivalent width are 110 eV, which favors a synchrotron origin of the X-ray emission. The characteristic variability timescale of 4 yr can be explained by the effects of fast synchrotron cooling and diffusive shock acceleration with a plausible magnetic field of 1 mG. The X-ray variability provides a new effective way of studying particle acceleration at supernova shocks.