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arXiv 1102.1213astro-ph.HE
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用朱雀卫星观测异常X射线脉冲星4U 0142+61的软、硬X射线辐射

Soft and Hard X-Ray Emissions from the Anomalous X-ray Pulsar 4U 0142+61 Observed with Suzaku

Teruaki Enoto, Kazuo Makishima, Kazuhiro Nakazawa, Motohide Kokubun, Madoka Kawaharada, Jun'ichi Kotoku, Noriaki Shibazaki

摘要:

2007年8月15日,朱雀号对异常X射线脉冲星4U 0142+61进行了观测,净曝光量为-100 ks,在0.4至~70 keV的能量带内被探测到。固有脉冲周期确定为8.68878 \pm 0.00005 s,与以前测量的外推法一致。宽带朱雀光谱使得第一次通过一颗卫星同时精确测量该物体的软硬成分成为可能。前者可以用两个黑体来再现,或者用共振回旋散射模型稍微好一点。当用共振回旋散射模型表示软分量时,硬分量可以用光子指数为Γh ~0.9的幂律近似,其高能截止被限制为>180 keV。假设在3.6 kpc的距离处的各向同性发射,软和硬分量的未吸收的1-10 keV和10-70 keV的亮度分别计算为2.8e+35 erg s^{-1}和6.8e+34 erg s^{-1}。它们的总和大约是估计的自旋下降光度的10^3倍。在30 ks的时间尺度上,硬组分表现出变化的证据,无论是在其正常化或脉冲形状。

英文摘要:

The anomalous X-ray pulsar 4U 0142+61 was observed with Suzaku on 2007 August 15 for a net exposure of -100 ks, and was detected in a 0.4 to ~70 keV energy band. The intrinsic pulse period was determined as 8.68878 \pm 0.00005 s, in agreement with an extrapolation from previous measurements. The broadband Suzaku spectra enabled a first simultaneous and accurate measurement of the soft and hard components of this object by a single satellite. The former can be reproduced by two blackbodies, or slightly better by a resonant cyclotron scattering model. The hard component can be approximated by a power-law of photon index Γh ~0.9 when the soft component is represented by the resonant cyclotron scattering model, and its high-energy cutoff is constrained as >180 keV. Assuming an isotropic emission at a distance of 3.6 kpc, the unabsorbed 1-10 keV and 10-70 keV luminosities of the soft and hard components are calculated as 2.8e+35 erg s^{-1} and 6.8e+34 erg s^{-1}, respectively. Their sum becomes ~10^3 times as large as the estimated spin-down luminosity. On a time scale of 30 ks, the hard component exhibited evidence of variations either in its normalization or pulse shape.

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