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arXiv 1310.0948astro-ph.HEastro-ph.SR
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X射线脉冲星4U 1909+07中回旋共振散射特征的可能探测

Possible detection of a cyclotron resonance scattering feature in the X-ray pulsar 4U 1909+07

Gaurava K. Jaisawal, Sachindra Naik, Biswajit Paul

摘要:

利用2010年11月2-3日的朱雀观测数据对高质量X射线脉冲双星4U 1909+07进行了定时和宽带光谱研究。脉冲星的脉冲周期估计为604.11+/-0.14秒。在高达~70 keV的X射线光变曲线中观察到脉动。脉冲轮廓被发现是强烈的能量依赖性:一个复杂的,多峰结构在低能量,成为一个简单的单峰在较高的能量。我们发现,1-70 keV脉冲平均连续谱可以用一个黑体和一个部分覆盖的指数截止正负幂律(NPEX)模型来拟合。在光谱中检测到6.4 keV处的弱铁荧光发射线。在光谱拟合的残余物中清楚地看到~44 keV处的吸收样特征,与所采用的连续模型无关。为了检查光谱中CRSF的可能存在,我们用蟹状星云的光谱对脉冲星光谱进行了归一化。所得到的Crab比率也显示出以~44 keV为中心的明显下降。我们进行了统计测试的光谱拟合的残留物,也对螃蟹光谱比,以确定的吸收功能的意义,并确定它作为一个CRSF的脉冲星。我们估计脉冲星相应的表面磁场为3.8 x 10^12高斯。

英文摘要:

We present timing and broad-band spectral studies of the high mass X-ray binary pulsar 4U 1909+07 using data from Suzaku observation during 2010 November 2-3. The pulse period of the pulsar is estimated to be 604.11+/-0.14 s. Pulsations are seen in the X-ray light curve up to ~70 keV. The pulse profile is found to be strongly energy-dependent: a complex, multi-peaked structure at low energy that becomes a simple single peak at higher energy. We found that the 1-70 keV pulse averaged continuum can be fitted by the sum of a black body and a partial covering Negative and Positive power-law with EXponential cutoff (NPEX) model. A weak iron fluorescence emission line at 6.4 keV was detected in the spectrum. An absorption like feature at ~44 keV was clearly seen in the residue of the spectral fitting, independent of the continuum model adopted. To check the possible presence of a CRSF in the spectrum, we normalized the pulsar spectrum with the spectrum of the Crab Nebula. The resulting Crab ratio also showed a clear dip centered at ~44 keV. We performed statistical tests on the residue of the spectral fitting and also on the Crab spectral ratio to determine the significance of the absorption like feature and identified it as a CRSF of the pulsar. We estimated the corresponding surface magnetic field of the pulsar to be 3.8 x 10^12 Gauss.

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