The Crab Nebula as a standard candle in very high-energy astrophysics
The Crab Nebula as a standard candle in very high-energy astrophysics
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DOI：
10.1051/0004-6361/201014108
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发表时间：
2010-08
期刊：
影响因子：
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通讯作者：
M. Meyer;D. Horns;H. Zechlin
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文献类型：
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作者：
M. Meyer;D. Horns;H. Zechlin
在~ 100 GeV以下的费米大面积望远镜（Fermi/LAT）和~ 60 GeV以上的地面成像空气切伦科夫望远镜（IACTs）首次在重叠能带上测量了蟹状星云在1 ~ 100 TeV之间的连续高能伽玛射线发射。为了跟进Hillas等人（1998）提出的现象学方法，使用宽带光谱和空间测量（从射电到< 1 GeV的低能伽马射线）来提取电子能谱的形状。虽然该模型可以很好地描述能量< 1 GeV的数据，但在包括所有相关的种子光子场并将平均磁场拟合为B = (124 +/- 6 (stat.) +15 /- 6 (sys.)) {\mu}G之后，预测的逆康普顿分量与费米/LAT和IACT的联合测量结果非常吻合。得到的宽频带逆康普顿分量与Fermi/LAT和IACTs数据的紧密匹配用于推导仪器特定的能量校准因子。这些因素可以用来结合Fermi/LAT和IACTs的数据，而不会受到共同能量尺度上的系统不确定性的影响。作为交叉校准的第一个应用，我们基于Fermi/LAT和H.E.S.S.地面切伦科夫望远镜的联合测量，得出了250 GeV到1 TeV之间的漫射伽马射线发射上限。最后，将Kennel & Coroniti（1984）的磁流体动力流动模型的预测结果与实测SED进行了比较。
The continuum high-energy gamma-ray emission between 1 GeV and 100 TeV from the Crab Nebula has been measured for the first time in overlapping energy bands by the Fermi large-area telescope (Fermi/LAT) below ~ 100 GeV and by ground-based imaging air Cherenkov telescopes (IACTs) above ~ 60 GeV. To follow up on the phenomenological approach suggested by Hillas et al. (1998), the broad band spectral and spatial measurement (from radio to low-energy gamma-rays < 1 GeV) is used to extract the shape of the electron spectrum. While this model per construction provides an excellent description of the data at energies < 1 GeV, the predicted inverse Compton component matches the combined Fermi/LAT and IACT measurements remarkably well after including all relevant seed photon fields and fitting the average magnetic field to B = (124 +/- 6 (stat.) +15 / -6 (sys.)) {\mu}G. The close match of the resulting broad band inverse Compton component with the combined Fermi/LAT and IACTs data is used to derive instrument specific energy-calibration factors. These factors can be used to combine data from Fermi/LAT and IACTs without suffering from systematic uncertainties on the common energy scale. As a first application of the cross calibration, we derive an upper limit to the diffuse gamma-ray emission between 250 GeV and 1 TeV based upon the combined measurements of Fermi/LAT and the H.E.S.S. ground-based Cherenkov telescopes. Finally, the predictions of the magneto-hydrodynamic flow model of Kennel & Coroniti (1984) are compared to the measured SED.