CHARACTERIZATION OF THE INNER KNOT OF THE CRAB: THE SITE OF THE GAMMA-RAY FLARES?
CHARACTERIZATION OF THE INNER KNOT OF THE CRAB: THE SITE OF THE GAMMA-RAY FLARES?
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螃蟹内结的特征：伽马射线耀斑的位置？
DOI：
10.1088/0004-637x/811/1/24
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发表时间：
2015
期刊：
影响因子：
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通讯作者：
M. Weisskopf
中科院分区：
文献类型：
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作者：
A. Rudy;D. Horns;A. deLuca;J. Kolodziejczak;A. Tennant;Yajie Yuan;Rolf Buehler;Jonathon Arons;R. Blandford;P. Caraveo;E. Costa;S. Funk;E. Hays;A. Lobanov;C. Max;M. Mayer;R. Mignani;S. O’Dell;R. Romani;M. Tavani;M. Weisskopf
最近γ射线天文学任务的一个特别有趣的结果是探测到蟹状星云的强大耀斑，这对目前对脉冲星风星云和加速机制的理解提出了挑战。为了寻找这些耀斑的产生地点，我们使用Keck，哈勃太空望远镜（HST）和钱德拉X射线天文台进行了多波长观测活动。由于γ射线耀斑的短时间尺度（γ 1？>天）表明一个小的发射区域，蟹状星云的内结（距离脉冲星约0.6弧秒）是这种耀斑的候选地点。本文描述了对内结的观测，试图了解它的性质以及与γ射线耀斑的可能关系。使用奇异值分解，HST图像的分析产生了与传统方法一致的结果，同时大大减少了一些不确定性。这些分析表明，结的内在属性（特别是大小和亮度）与其（预计）与脉冲星的分离有关。内结的这种表征有助于在假设结位于冲击表面附近的情况下约束标准冲击模型参数。虽然标准激波模型在几个方面给出了很好的一致性，但仍然存在两个难题：（a）观测到的相对于脉冲星-结分离的结角尺寸比预期的小得多;（B）可变的高度偏振（由其他人报道）很难与高度相对论性的下游流相协调。然而，内结的红外光通量与加速星云大部分光发射粒子的激波略微一致。
A particularly intriguing recent result from γ-ray astronomy missions is the detection of powerful flares from the Crab Nebula, which challenges the current understanding of pulsar wind nebulae and acceleration mechanisms. To search for the production site(s) of these flares, we conducted a multi-wavelength observing campaign using Keck, the Hubble Space Telescope (HST), and the Chandra X-ray Observatory. As the short timescales of the γ-ray flares ( ≲ 1 ?> day) suggest a small emitting region, the Crab’s inner knot (about 0.6 arcsec from the pulsar) is a candidate site for such flaring. This paper describes observations of the inner knot, seeking to understand its nature and possible relationship with γ-ray flares. Using singular-value decomposition, analysis of the HST images yielded results consistent with traditional methods while substantially reducing some uncertainties. These analyses show that the knot’s intrinsic properties (especially size and brightness) are correlated with its (projected) separation from the pulsar. This characterization of the inner knot helps in constraining standard shock model parameters, under the assumption that the knot lies near the shocked surface. While the standard shock model gives good agreement in several respects, two puzzles persist: (a) the observed angular size of the knot relative to the pulsar–knot separation is much smaller than expected; and (b) the variable high degree of polarization (reported by others) is difficult to reconcile with a highly relativistic downstream flow. However, the IR–optical flux of the inner knot is marginally consistent with the shock accelerating most of the Nebula’s optical-emitting particles.