The Crab pulsar in the 0.75-30 MeV range as seen by CGRO COMPTEL -: A coherent high-energy picture from soft X-rays up to high-energy γ-rays
The Crab pulsar in the 0.75-30 MeV range as seen by CGRO COMPTEL -: A coherent high-energy picture from soft X-rays up to high-energy γ-rays
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DOI：
10.1051/0004-6361:20011256
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发表时间：
2001-11-01
影响因子：
6.5
通讯作者：
McConnell, ML
中科院分区：
文献类型：
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作者：
Kuiper, L;Hermsen, W;McConnell, ML
我们使用康普顿伽马射线天文台 (CGRO) 上的成像康普顿望远镜 COMPTEL 在其 9 年任务中收集的数据，展示了蟹状脉冲星在 0.75-30 MeV 能量窗口中的时间平均特征。利用蟹状星云上超长时间的 COMPTEL 曝光，我们能够获得显着改进的蟹状星云和脉冲星发射的 COMPTEL 光谱，并首次准确确定低能伽马射线下作为能量函数的脉冲轮廓。这些定时数据显示了著名的主脉冲和第二脉冲，其相距约为 0.4，具有强桥发射，与 ROSAT HRI、BeppoSAX LECS、MECS 和 PDS 的软/硬 X 射线能量、CGRO BATSE 的软伽马射线和 CGRO EGRET 的高能伽马射线获得的数据一起进行研究，以便获得蟹状脉冲星的相干高能图像0.1 keV 至 10 GeV。蟹状脉冲星的脉冲轮廓形态随着能量的变化而不断变化：第二个脉冲和桥发射的强度相对于第一个脉冲的强度增加，能量增加到大约 1 MeV。在高于 1 MeV 的 COMPTEL 能量范围内，会发生突然的形态变化：第一个脉冲再次主导第二个脉冲，并且桥发射失去重要性，使得高于 30 MeV 的脉冲轮廓与在光学波长处观察到的脉冲轮廓相似。在 0.1 keV-10 GeV 能量间隔上一致应用的 7 个窄相位切片中进行的脉冲相位分辨光谱分析表明，脉冲发射可以凭经验用 3 个不同的光谱分量来描述： i) 幂律发射分量（1 keV-5 GeV；光子指数 2.022+/-0.014），存在于两个脉冲的相位间隔中； ii) 描述相同脉冲相位间隔中存在的软（小于或类似于 100 keV）过量发射所需的弯曲光谱分量； iii) 反映从 0.1 keV 到类似于 10 MeV 的桥发射的宽曲线光谱分量。该宽光谱分量以近似三角形的形式在整个脉冲轮廓上同相延伸，在第二个脉冲下达到峰值。 Cheng 等人最近对具有外磁层间隙加速的三维脉冲星磁层进行了模型计算。 (2000)目前看来在解释蟹状脉冲星的上述复杂高能特征方面最成功。
We present the time-averaged characteristics of the Crab pulsar in the 0.75-30 MeV energy window using data from the imaging Compton Telescope COMPTEL aboard the Compton Gamma-Ray Observatory (CGRO) collected over its 9 year mission. Exploiting the exceptionally long COMPTEL exposure on the Crab allowed us to derive significantly improved COMPTEL spectra for the Crab nebula and pulsar emissions, and for the first time to accurately determine at low-energy gamma -rays the pulse profile as a function of energy. These timing data, showing the well-known main pulse and second pulse at a phase separation of similar to0.4 with strong bridge emission, are studied together with data obtained at soft/hard X-ray energies from the ROSAT HRI, BeppoSAX LECS, MECS and PDS, at soft gamma -rays from CGRO BATSE and at high-energy gamma -rays from CGRO EGRET in order to obtain a coherent high-energy picture of the Crab pulsar from 0.1 keV up to 10 GeV. The morphology of the pulse profile of the Crab pulsar is continuously changing as a function of energy: the intensities of both the second pulse and the bridge emission increase relative to that of the first pulse for increasing energies up to similar to1 MeV. Over the COMPTEL energy range above 1 MeV an abrupt morphology change happens: the first pulse becomes again dominant over the second pulse and the bridge emission loses significance such that the pulse profile above 30 MeV is similar to the one observed at optical wavelengths. A pulse-phase-resolved spectral analysis performed in 7 narrow phase slices consistently applied over the 0.1 keV-10 GeV energy interval shows that the pulsed emission can empirically be described with 3 distinct spectral components: i) a power-law emission component (1 keV-5 GeV; photon index 2.022+/-0.014), present in the phase intervals of the two pulses; ii) a curved spectral component required to describe soft (less than or similar to 100 keV) excess emission present in the same pulse-phase intervals; iii) a broad curved spectral component reflecting the bridge emission from 0.1 keV to similar to 10 MeV. This broad spectral component extends in phase over the full pulse profile in an approximately triangular shape, peaking under the second pulse. Recent model calculations for a three-dimensional pulsar magnetosphere with outer magnetospheric gap acceleration by Cheng et al. (2000) appear at present most successful in explaining the above complex high-energy characteristics of the Crab pulsar.