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arXiv 1012.3211astro-ph.HEastro-ph.SR
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用INTEGRAL/IBIS对2S 0114+65进行长期硬X射线监测

Long-term Hard X-ray Monitoring of 2S 0114+65 with INTEGRAL/IBIS

Wei Wang

摘要:

介绍了2003 - 2008年利用INTEGRAL/IBIS对高质量X射线双星2S 0114+65进行长期硬X射线监测的结果。2S 0114+65是一个变硬X射线源,当2S 0114+65亮时,脉冲周期从2003 - 2008年的$\sim 2.67$小时到2.63小时,中子星的自旋速率为$\sim 1.09\times 10^{-6}$ s s $^{-1}$ .与以前报道的自旋上升速率相比,2S 0114+65中的中子星的自旋上升速率正在加速。2S 0114+65在18 - 100 keV波段的光谱性质随轨道相位的变化而变化。幂律光子指数随轨道位相的变化与硬X射线通量有关,$E_{\rm cut}$随轨道位相的变化与硬X射线通量呈正相关,说明硬谱在光变曲线的最大值处。光谱性质随轨道相位的变化表明2S 0114+65是一个高度遮蔽的双星系统。在某些观测革命中,探测到70 keV以上的硬X射线尾。结合JEM-X和IBIS数据,研究了3 - 100 keV能量范围内硬X射线尾的特征。2S 0114+65的3 - 100 keV能谱符合高能量截止的吸收幂律模型。我们发现,只有在柱密度很低的情况下,才能探测到硬X射线尾。因此,高的柱密度导致了这个风馈中子星吸积双星中硬X射线尾的消失。

英文摘要:

(abridged) We present the results of the long-term hard X-ray monitoring of the high mass X-ray binary 2S 0114+65 with INTEGRAL/IBIS from 2003 to 2008. 2S 0114+65 is a variable hard X-ray source, when 2S 0114+65 was bright, we found a pulse period evolution of $\sim 2.67$ hour to 2.63 hour from 2003 -- 2008, with a spin-up rate of the neutron star $\sim 1.09\times 10^{-6}$ s s$^{-1}$. Compared with the previous reported spin-up rate, the spin-up rate of the neutron star in 2S 0114+65 is accelerating. The spectral properties of 2S 0114+65 in the band of 18 -- 100 keV which changed with the orbital phases. The variation of the power-law photon index over orbital phase anticorrelates with hard X-ray flux, and the variation of $E_{\rm cut}$ has a positive correlation with the hard X-ray flux, implying that the harder spectrum at the maximum of the light curve. The variations of spectral properties over orbital phase suggested 2S 0114+65 as a highly obscured binary system. In some observational revolutions, hard X-ray tails above 70 keV are detected. We study the characteristics of the hard X-ray tails combining JEM-X and IBIS data in the energy range of 3 -- 100 keV. The 3 -- 100 keV spectra of 2S 0114+65 are generally fitted by an absorbed power-law model with high energy cutoff. We discover that the hard X-ray tails are only detected when column density is very low. Thus, high column density leads to disappearance of the hard X-ray tails in this wind-fed neutron star accretion binary.

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