THE HIGH-ENERGY EMISSION OF THE CRAB NEBULA FROM 20 keV TO 6 MeV WITH INTEGRAL SPI
THE HIGH-ENERGY EMISSION OF THE CRAB NEBULA FROM 20 keV TO 6 MeV WITH INTEGRAL SPI
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DOI：
10.1088/0004-637x/704/1/17
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发表时间：
2009-09
期刊：
影响因子：
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通讯作者：
E. Jourdain;J. Roques
中科院分区：
文献类型：
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作者：
E. Jourdain;J. Roques
自2003年以来，国际伽马射线天体物理实验室任务上的SPI光谱仪定期观测蟹状星云。我们报告了分布在5.5年内的观测，并研究了这一引人注目的源在硬X射线领域的强度和光谱形状的变异性，最高可达几兆电子伏特。虽然单幂定律模型在X射线域(平均光子指数∼2.05)和MeV域(光子指数∼2.23)中给出了很好的描述，但关键信息包含在斜率随能量介于这两个值之间的演化中。这项研究是通过个人观测和长持续时间(∼400k)平均谱进行的。排放的稳定性是显著的，排除了单一的幂定律模型。在100keV以下和100keV以上测量的斜率分别与X射线和MeV区域报告的最新值完全一致，但没有显示局部断点。这表明发射在100keV附近逐渐变软，因此是一个连续的演化过程，而不是实际的机制参数变化。在MeV区，在5-6 MeV范围内，没有明显偏离所提出的幂定律模型。最后，我们利用仪器的光谱能力来寻找先前报道的覆盖能量范围内的光谱特征，对于400k时间尺度上任何重要的回旋或湮灭发射，结果都是否定的。除了科学结果外，还明确展示了SPI仪器的性能和可靠性，并详细说明了最合适的分析方法。
The SPI spectrometer aboard the International Gamma-Ray Astrophysics Laboratory mission regularly observes the Crab Nebula since 2003. We report on observations distributed over 5.5 years and investigate the variability of the intensity and spectral shape of this remarkable source in the hard X-rays domain up to a few MeV. While single power-law models give a good description in the X-ray domain (mean photon index ∼ 2.05) and MeV domain (photon index ∼ 2.23), crucial information is contained in the evolution of the slope with energy between these two values. This study has been carried out through individual observations and long duration (∼ 400 ks) averaged spectra. The stability of the emission is remarkable and excludes a single power-law model. The slopes measured below and above 100 keV agree perfectly with the last values reported in the X-ray and MeV regions, respectively, but without indication of a localized break point. This suggests a gradual softening in the emission around 100 keV and thus a continuous evolution rather than an actual change in the mechanism parameters. In the MeV region, no significant deviation from the proposed power-law model is visible up to 5–6 MeV. Finally, we take advantage of the spectroscopic capability of the instrument to seek for previously reported spectral features in the covered energy range with negative results for any significant cyclotron or annihilation emission on 400 ks timescales. Beyond the scientific results, the performance and reliability of the SPI instrument is explicitly demonstrated, with some details about the most appropriate analysis method.