Long‐term hard X‐ray monitoring of 2S 0114+65 with INTEGRAL/IBIS
Long‐term hard X‐ray monitoring of 2S 0114+65 with INTEGRAL/IBIS
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DOI：
10.1111/j.1365-2966.2010.18192.x
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发表时间：
2010-12
影响因子：
4.8
通讯作者：
Wei Wang
中科院分区：
文献类型：
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作者：
Wei Wang
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。2S0114 + 65是一个可变硬X射线源，在20~100keV能量范围内，由于吸积率的变化，其X射线亮度为1035~4 × 1036ergs-1。在2S 0114 + 65明亮时的几次观测中，我们发现从2003年到2008年的脉冲周期演化为2.67 h到2.63 h，中子星星的自旋加速率为1.09 x 10 ― 6 s ― 1。与先前报道的自旋上升速率相比，2S 0114 + 65中子星星的自旋上升速率正在加速。2S 0114 + 65在18 - 100 keV波段随轨道相位变化的光谱特性通常可以用高能指数截止的幂律模型来描述。幂律光子指数随轨道位相的变化与硬X射线通量有关，E截的变化与硬X射线通量呈正相关，表明光变曲线最大值处的光谱较硬。光谱性质随轨道相位的变化表明2S0114 + 65是一个高度遮蔽的双星系统。在一些观测革命中，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。2S0114 + 65的3 - 100keV能谱一般用高能截止的吸收幂律模型拟合。我们发现，只有当柱密度很低时，才能探测到硬X射线尾。因此，高的柱密度导致了这种风馈中子星星吸积双星中硬X射线尾的消失。我们的研究结果将有助于理解这类特殊的高质量X射线双星中的超慢脉动中子星的起源、演化和性质。
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 with X-ray luminosities of 10 35 ―4 × 10 36 erg s ―1 from 20 to 100 keV due to accretion rate changes in different orbital phases. In several observations when 2S 0114+65 was bright, we found a pulse period evolution of ∼2.67 h to 2.63 h from 2003 to 2008, with a spin-up rate of the neutron star ∼1.09 x 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 18-100 keV band which changed with the orbital phases generally could be described with a power-law model with a high-energy exponential cut-off. The variation of the power-law photon index over orbital phase anticorrelates with hard X-ray flux, and the variation of E cut has a positive correlation with the hard X-ray flux, implying a 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 cut-off. We discover that the hard X-ray tails are only detected when the column density is very low. Thus, a high column density leads to the disappearance of the hard X-ray tails in this wind-fed neutron star accretion binary. Our results would help to understand the origin, evolution and properties of this peculiar class of superslow pulsation neutron stars in high-mass X-ray binaries.