蟹状星云Chndra卫星观测数据的X射线谱分析

首次用Chandra卫星资料详尽的对蟹状星云弧秒尺度区域以及主要的活动区进行了X射线谱分析．测得了蟹状星云中的主要活动区：如环面(torus)，结节(knots)，亮条纹(wisp)，喷流(东南方向)，反向喷流(西北方向)的光子谱指数(photon index)．同时在环面区，分析了光子谱指数随径向的分布．有迹象表明，在内环中可能存在一个在理论和观测上以前都没有提及到的粒子加速区．结节是整个蟹状星云中光子谱指数最低的地方，这表明粒子在这些区域得到加速．东南方向的喷流的谱指数和环面内暗区的谱指数类似，而西北方向的反向喷流具有最大的光子谱指数．得到的结果同XMM(X—Ray Multi—Mirror Mission)卫星的结果进行比较，两基本一致．

Spatially Resolved X-ray Photon Index of the Crab Nebula with Chandra Data

The X-ray synchrotron spectra of the Crab Nebula at arc-second scale were measured from observations with the Chandra X-ray Observatory. In addition to the Crab Nebula as a whole, we measured the spectra of the torus, the knots, the wisp, the jet (southeast) and its counter-jet (northwest). We obtained the radial distribution of the photon index of the torus. We find evidence for an acceleration region between the Crab pulsar and the X-ray inner ring that has not been anticipated by previous observations and theories. The knots have the lowest spectral index, which indicates that they are the sites of particle acceleration. The photon index of the main (southeast) jet is similar to that in the faintest area of the torus. The northwest counter-jet has the greatest photon index in the Crab Nebula. The variations of the photon index are obvious along the radial distribution of the torus and the ejecting direction of the jet (southeast). We compared our results with those of XMM(X-Ray Multi-Mirror Mission) and find that the main data match quite well. The data we used, released by the CXC (Chandra X-ray Center), is OID (observe ID) 2000, taken on April 6, 2001. Its observation time is 27.292 ks imaged on the ACIS (Advanced Camera for Imaging and Spectroscopy) -7 CCD chip. We analyzed these data with the CIAO (Chandra Interactive Analysis of Observations) version 2.3 analysis package, the CALDB version 2.21 calibration database, the ACISSPEC spectrum-extracting tool, and the Sherpa spectrum-fitting program. In every selected area of the Crab Nebula, we fit the 0.4 - 5 keV spectrum with a single power-law continuum with interstellar absorption. The smallest area we measured is larger than Chandra's PSF (Point Spread Function) with 0.5 arc-second.