We investigate time variations and detailed spatial structures of X-ray synchrotron emission in the northeastern limb of SN 1006, using two Chandra observations taken in 2000 and 2008. We extract spectra from a number of small (about 10") regions. After taking account of proper motion and isolating the synchrotron from the thermal emission, we study time variations in the synchrotron emission in the small regions. We find that there are no regions showing strong flux variations. Our analysis shows an apparent flux decline in the overall synchrotron flux of about 4% at high energies, but we suspect that this is mostly a calibration effect, and that flux is actually constant to about 1%. This is much less than the variation found in other remnants where it was used to infer magnetic-field strengths up to 1 mG. We attribute the lack of variability to the smoothness of the synchrotron morphology, in contrast to the small-scale knots found to be variable in other remnants. The smoothness is to be expected for a Type Ia remnant encountering uniform material. Finally we find a spatial correlation between the flux and the cut-off frequency in synchrotron emission. The simplest interpretation is that the cut-off frequency depends on the magnetic-field strength. This would require that the maximum energy of accelerated electrons is not limited by synchrotron losses, but by some other effect. Alternatively, the rate of particle injection and acceleration may vary due to some effect not yet accounted for, such as a dependence on shock obliquity.
The loss-limited electron energy in SN 1006: effects of the shock velocity and of the diffusion process
SN 1006同步加速器X射线辐射的光谱形状揭示了辐射损失在形成电子光谱的高能尾部中所起的基本作用。我们分析了XMM-牛顿SN 1006大型程序的数据，并确认在两个非热肢的损失限制模型正确地描述了所观察到的光谱。我们研究了观测到的同步辐射截止能量在壳层上变化的物理根源。我们调查的冲击速度和电子陀螺因子所起的作用。我们发现，同步加速器X射线辐射的截止能量在激波经历最高平均速率的区域达到最大值。这一结果与损失限制框架一致。我们还发现，在两个非热肢体的SN 1006的电子加速收益接近玻姆扩散极限，陀螺因子在1.5-4的范围内。最后，我们调查可能的解释，在热肢的截止能量测量值低。
X-rays Emission: a novel tool to detect Extensive Air Showers
Gran Sasso Science Institute（格兰萨索科学研究所）；INFN-Laboratori Nazionali del Gran Sasso（意大利国家核物理研究所格兰萨索国家实验室）；NASA Goddard Space Flight Center（美国宇航局戈达德太空飞行中心）；Columbia University（哥伦比亚大学）；Pennsylvania State University（宾夕法尼亚州立大学）
The connection between supernova remnants and the Galactic magnetic field: An analysis of quasi-parallel and quasi-perpendicular cosmic ray acceleration for the axisymmetric sample
