OBSERVATION AND SPECTRAL MEASUREMENTS OF THE CRAB NEBULA WITH MILAGRO
OBSERVATION AND SPECTRAL MEASUREMENTS OF THE CRAB NEBULA WITH MILAGRO
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DOI：
10.1088/0004-637x/750/1/63
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发表时间：
2011-10
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通讯作者：
A. Abdo;B. Allen;R. Atkins;T. Aune;W. Benbow;D. Berley;E. Blaufuss;E. Bonamente;J. Bussons;C. Chen;G. Christopher;D. Coyne;T. DeYoung;B. Dingus;D. Dorfan;R. Ellsworth;A. Falcone;L. Fleysher;R. Fleysher;J. Galbraith-Frew;M. González;J. Goodman;T. Haines;E. Hays;C. Hoffman;P. Hüntemeyer;L. Kelley;B. Kolterman;C. Lansdell;J. Linnemann;J. Mccullough;J. Mcenery;T. Morgan;A. Mincer;M. Morales;P. Némethy;D. Noyes;J. Pretz;J. Ryan;F. Samuelson;P. S. Saz Parkinson;A. Shoup;G. Sinnis;A. Smith;G. Sullivan;V. Vasileiou;G. Walker;M. Wascko;D. Williams;S. Westerhoff;G. Yodh
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作者：
A. Abdo;B. Allen;R. Atkins;T. Aune;W. Benbow;D. Berley;E. Blaufuss;E. Bonamente;J. Bussons;C. Chen;G. Christopher;D. Coyne;T. DeYoung;B. Dingus;D. Dorfan;R. Ellsworth;A. Falcone;L. Fleysher;R. Fleysher;J. Galbraith-Frew;M. González;J. Goodman;T. Haines;E. Hays;C. Hoffman;P. Hüntemeyer;L. Kelley;B. Kolterman;C. Lansdell;J. Linnemann;J. Mccullough;J. Mcenery;T. Morgan;A. Mincer;M. Morales;P. Némethy;D. Noyes;J. Pretz;J. Ryan;F. Samuelson;P. S. Saz Parkinson;A. Shoup;G. Sinnis;A. Smith;G. Sullivan;V. Vasileiou;G. Walker;M. Wascko;D. Williams;S. Westerhoff;G. Yodh
蟹状星云是用米拉格罗实验发现的，在实验的整个生命周期内，其统计显著性为17个标准差。通过观察到达地面的粒子足迹，该实验对大约100 GeV-100 TeV的伽马射线空气阵雨非常敏感。在地面上记录光子信号的探测器的分数是主粒子能量的合适代表，并已被用于测量蟹状星云在~ 1和~ 100 TeV之间的光子能谱。TeV发射被认为是由高能电子群对环境光子的逆康普顿上散射引起的。在能谱中TeV陡增或截止的位置揭示了潜在电子居群的重要细节。我们描述了从更丰富的强子事件中区分伽马射线事件的实验和技术。我们描述了计算来自蟹状星云的过剩的重要性，以及如何拟合能谱。在~ 1 TeV和~ 100 TeV之间，利用简单幂律假设得到的2005年9月至2008年3月数据的微分光子能谱，包括统计误差，为（6.5±0.4）× 10−14(E/10 TeV)−3.1±0.1(cm2 s TeV)−1。考虑到可能的指数截断，光子能谱拟合为（2.5+0.7−0.4）× 10−12(E/3 TeV)−2.5±0.4exp(−E/32+39−18 TeV) (cm2 s TeV)−1。结果在总通量中有~ 30%的系统不确定度，在引用的幂律指数中有~ 0.1的系统不确定度。总能量标度的不确定性已被这些误差所吸收。将光谱指数固定在IACT实验测量的低于1 TeV的值上（2.4-2.6），与Milagro数据的拟合表明，螃蟹显示出光谱陡峭或在大约20-40 TeV之间的截止。
The Crab Nebula was detected with the Milagro experiment at a statistical significance of 17 standard deviations over the lifetime of the experiment. The experiment was sensitive to approximately 100 GeV–100 TeV gamma-ray air showers by observing the particle footprint reaching the ground. The fraction of detectors recording signals from photons at the ground is a suitable proxy for the energy of the primary particle and has been used to measure the photon energy spectrum of the Crab Nebula between ∼1 and ∼100 TeV. The TeV emission is believed to be caused by inverse-Compton upscattering of ambient photons by an energetic electron population. The location of a TeV steepening or cutoff in the energy spectrum reveals important details about the underlying electron population. We describe the experiment and the technique for distinguishing gamma-ray events from the much more-abundant hadronic events. We describe the calculation of the significance of the excess from the Crab and how the energy spectrum is fitted. The differential photon energy spectrum, including the statistical errors from the fit, obtained using a simple power-law hypothesis for data between 2005 September and 2008 March is (6.5 ± 0.4) × 10−14(E/10 TeV)−3.1±0.1(cm2 s TeV )−1 between ∼1 TeV and ∼100 TeV. Allowing for a possible exponential cutoff, the photon energy spectrum is fitted as (2.5+0.7− 0.4) × 10−12(E/3 TeV)−2.5 ± 0.4exp (− E/32+39− 18 TeV) (cm2 s TeV)−1. The results are subject to an ∼30% systematic uncertainty in the overall flux and an ∼0.1 systematic uncertainty in the power-law indices quoted. Uncertainty in the overall energy scale has been absorbed into these errors. Fixing the spectral index to values that have been measured below 1 TeV by IACT experiments (2.4–2.6), the fit to the Milagro data suggests that Crab exhibits a spectral steepening or cutoff between about 20–40 TeV.