The 0.1-100 keV Spectrum of Centaurus X-3: Pulse Phase Spectroscopy of the Cyclotron Line and Magnetic Field Structure
The 0.1-100 keV Spectrum of Centaurus X-3: Pulse Phase Spectroscopy of the Cyclotron Line and Magnetic Field Structure
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DOI：
10.1086/308336
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发表时间：
2000-02
期刊：
影响因子：
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通讯作者：
L. Burderi;T. di Salvo;N. Robba;A. L. La Barbera;M. Guainazzi
中科院分区：
文献类型：
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作者：
L. Burderi;T. di Salvo;N. Robba;A. L. La Barbera;M. Guainazzi
本文报道了BeppoSAX卫星观测到的X射线脉冲星半人马座X-3的光谱和时间分析。宽带光谱（0.12-100 keV）可以通过吸收幂律很好地描述，该定律由~14 keV的高能翻转（e折叠能量~8 keV）加上~6.7 keV的铁发射线修改。还存在低于1 keV的软过量。解释为黑体（kT <$0.1 keV），它相当于总未吸收通量的58%。这一成分似乎是由位于磁层的不透明壳层对初级辐射进行再处理而产生的。在~30 keV的吸收功能也存在。解释为回旋加速线，经过引力红移校正后，这对应于~3.5 × 1012 G的表面磁场。相位分辨光谱揭示了约8 keV的回旋共振能量沿着脉冲轮廓的变化。特别地，从上升开始，线能量沿着峰从~36 keV沿着减小到~28 keV。回旋线能量的不对称变化可以通过假设偶极磁场相对于中子星星中心的偏移来解释。的光谱结果进行了讨论，从磁帽，软光子发生康普顿化的发射。软光子可能来自磁共振双康普顿散射或来自在磁层表面重新处理的初级辐射对极盖的照射，这是一种类似于黑洞光谱形成的反馈机制。
We report spectral and temporal analysis of the X-ray pulsar Centaurus X-3 out of eclipse observed by BeppoSAX. The broadband spectrum (0.12-100 keV) is well described by an absorbed power law modified by a high-energy rollover at ~14 keV (e-folding energy ~8 keV) plus an iron emission line at ~6.7 keV. A soft excess below 1 keV is also present. Interpreted as a blackbody (kT ≃ 0.1 keV), it corresponds to 58% of the total unabsorbed flux. This component seems to originate from reprocessing of the primary radiation by an opaque shell located at the magnetosphere. An absorption feature at ~30 keV is also present. Interpreted as a cyclotron line, after correction for gravitational redshift, this corresponds to a surface magnetic field of ~3.5 × 1012 G. Phase-resolved spectroscopy reveals a variation by about 8 keV of the cyclotron resonance energy along the pulse profile. In particular, the line energy decreases from ~36 to ~28 keV along the peak, starting from the ascent. The asymmetric variations of the cyclotron line energy can be explained by assuming an offset of the dipolar magnetic field with respect to the neutron star center. The spectral results are discussed in terms of emission from magnetic caps, where Comptonization of soft photons occurs. The soft photons could come from either magnetically resonant double Compton scattering or from illumination of the polar cap by the primary radiation reprocessed at the magnetospheric surface, a feedback mechanism similar to that proposed for the formation of black hole spectra.