论文标题
X射线极化测量值的中子恒星低质量X射线二进制CYG X-2的积聚几何形状
Accretion geometry of the neutron star low mass X-ray binary Cyg X-2 from X-ray polarization measurements
论文作者
论文摘要
我们报告了ixpe，nicer和Integrally同时观察到的明亮中性恒星低质量X射线二进制二进制二进制二进制二进制二进制CYG X-2的观察性运动的光谱极光结果。与先前的结果一致，宽带频谱的特征是低能量的成分，归因于$ kt _ {\ rm in} \ in} \ $ 1 keV的积聚光盘，加上温度$ kt _ {\ rm e} = 3 $ kev and optical $ kev and optical $ $ $ $ $ $ $ $ $ $ 4的热等离子体中的不饱和血浆中的不饱和综合。我们测量2-8 kev频段$ p = 1.8 \ pm 0.3 $ 0.3 $ and偏振角$ ϕ = 140^{\ circ} \ pm 4^{\ circ} $的极化度，与以前通过OSO-8的X射线极化测量结果一致，与以前从该电台开始的无线电喷射方向相一致。虽然圆盘频谱分量的极化与IXPE数据的约束较差，但构成的发射度具有极化度$ p = 4.0 \ pm 0.7 $ 0.7 $ 0.7 $ 0.7 $ 0.7 $ 0.7 $，并且与无线电射流对齐的极化角度。我们的结果强烈利用中子星表面的扩散层作为极化信号的主要来源。但是，如铁荧光线的存在所示，我们不能排除积聚盘反射的重大贡献。
We report spectro-polarimetric results of an observational campaign of the bright neutron star low-mass X-ray binary Cyg X-2 simultaneously observed by IXPE, NICER and INTEGRAL. Consistently with previous results, the broad-band spectrum is characterized by a lower-energy component, attributed to the accretion disc with $kT_{\rm in} \approx$ 1 keV, plus unsaturated Comptonization in thermal plasma with temperature $kT_{\rm e} = 3$ keV and optical depth $τ\approx 4$, assuming a slab geometry. We measure the polarization degree in the 2-8 keV band $P=1.8 \pm 0.3$ per cent and polarization angle $ϕ= 140^{\circ} \pm 4^{\circ}$, consistent with the previous X-ray polarimetric measurements by OSO-8 as well as with the direction of the radio jet which was earlier observed from the source. While polarization of the disc spectral component is poorly constrained with the IXPE data, the Comptonized emission has a polarization degree $P =4.0 \pm 0.7$ per cent and a polarization angle aligned with the radio jet. Our results strongly favour a spreading layer at the neutron star surface as the main source of the polarization signal. However, we cannot exclude a significant contribution from reflection off the accretion disc, as indicated by the presence of the iron fluorescence line.
