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arXiv 0801.4679astro-ph
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小麦哲伦云的XMM-牛顿观测:6.85秒脉冲星XTE J0103-728的X射线爆发

XMM-Newton observations of the Small Magellanic Cloud: X-ray outburst of the 6.85 s pulsar XTE J0103-728

F. Haberl, W. Pietsch

摘要:

2006年10月,在小麦哲伦云(SMC)方向的XMM-牛顿观测期间,我们看到了明亮的X射线瞬变。EPIC数据使我们能够准确地定位源,并调查其时间和光谱行为。从EPIC数据中提取了覆盖0.2-10 keV的X射线谱和不同能带的脉冲轮廓。在EPIC-PN数据中检测到的6.85 s脉冲明确地识别了XTE J 0103 -728的瞬变,RXTE发现了6.85 s脉冲星。在XMM-牛顿观测期间的X射线光变曲线显示了源的耀斑活动,其强度在10分钟内变化了两倍。用一个简单的吸收幂律模型的脉冲相位平均光谱表明系统的残差,可以占第二个发射组件。对于包含黑体发射、热等离子体发射或来自吸积盘(盘-黑体)的发射的模型,后者产生物理上敏感的参数。幂律的光子指数约为0.4,表明光谱相对较硬。0.2-10 keV的光度为2x 10 ^{37},其中约3%来自盘黑体分量。过量辐射的一个可能来源是来自中子星的硬X射线被吸积盘内边缘附近的光学厚材料再处理。从时间分析中,我们确定脉冲周期为6.85401(1)s,表明自2003年5月发现XTE J 0103 -728以来,平均每年约0.0017 s的自旋下降。X射线性质和Be星的鉴定证实XTE J 0103 -728是SMC中的Be/X射线双星瞬变。

英文摘要:

A bright X-ray transient was seen during an XMM-Newton observation in the direction of the Small Magellanic Cloud (SMC) in October 2006. The EPIC data allow us to accurately locate the source and to investigate its temporal and spectral behaviour. X-ray spectra covering 0.2-10 keV and pulse profiles in different energy bands were extracted from the EPIC data. The detection of 6.85 s pulsations in the EPIC-PN data unambiguously identifies the transient with XTE J0103-728, discovered as 6.85 s pulsar by RXTE. The X-ray light curve during the XMM-Newton observation shows flaring activity of the source with intensity changes by a factor of two within 10 minutes. Modelling of pulse-phase averaged spectra with a simple absorbed power-law indicates systematic residuals which can be accounted for by a second emission component. For models implying blackbody emission, thermal plasma emission or emission from the accretion disk (disk-blackbody), the latter yields physically sensible parameters. The photon index of the power-law of ~0.4 indicates a relatively hard spectrum. The 0.2-10 keV luminosity was 2x10^{37} with a contribution of ~3% from the disk-blackbody component. A likely origin for the excess emission is reprocessing of hard X-rays from the neutron star by optically thick material near the inner edge of an accretion disk. From a timing analysis we determine the pulse period to 6.85401(1) s indicating an average spin-down of ~0.0017 s per year since the discovery of XTE J0103-728 in May 2003. The X-ray properties and the identification with a Be star confirm XTE J0103-728 as Be/X-ray binary transient in the SMC.

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