Insight-HXMT 对 Scorpius X-1 硬X射线尾的探测
Insight-HXMT Detections of Hard X-ray Tails in Scorpius X-1
AI总结：
本文利用 Insight-HXMT 观测数据在 Scorpius X-1 中发现硬X射线尾，通过多能段谱联合拟合揭示其 HB 和 NB 分支的硬尾可能源于电子康普顿化，并指出 FB 分支硬尾具有不同起源。
摘要：
利用硬X射线调制望远镜（Insight-HXMT）高能（HE）探测器对 Scorpius X-1 在 2018 年的观测数据，我们在约 30-200 keV 的硬X射线谱中搜寻硬X射线尾。在整个硬度-强度图的 Z 轨迹上均发现了硬X射线尾，并且它们从水平分支（HB）经正常分支（NB）到耀发分支（FB）逐渐变硬并减弱。通过比较 Cyg X-1 和 Sco X-1 的硬X射线谱，得出结论：Cyg X-1 的硬X射线谱表现出高能截断，暗示其内部存在热冕，但 Sco X-1 的硬X射线谱中并未显现这种高能截断。将约 2-200 keV 的 HE 谱与 Sco X-1 的中能和低能谱进行联合拟合，结果表明：自由下落至中子星（NS）的高能电子或 NS 与吸积盘之间边界层中的混合电子对 NS 辐射光子的上散射康普顿化，可能导致了 Sco X-1 在 HB 和 NB 上的硬X射线尾，但这两种机制均无法解释 FB 上的硬X射线尾。本文还讨论了 FB 特殊硬X射线尾的一些可能起源。
英文摘要：
Using the observations of the high-energy (HE) detector of the Hard X-ray Modulation Telescope (Insight-HXMT) for Scorpius X-1 in 2018, we search for hard X-ray tails in the hard X-ray spectra in ~30-200 keV. The hard X-ray tails are found throughout the Z-track on the hardness-intensity diagram and they harden and fade away from the horizontal branch (HB), through the normal branch (NB), to the flaring branch (FB). Comparing the hard X-ray spectra between Cyg X-1 and Sco X-1, it is concluded that the hard X-ray spectrum of Cyg X-1 shows high-energy cutoff, implying a hot corona in it, but the high-energy cutoff does not reveal in the hard X-ray spectrum of Sco X-1. Jointly fitting the HE spectrum with the medium-energy and low-energy spectra of Sco X-1 in ~2-200 keV, it is suggested that the upscattering Comptonization of the neutron star (NS) emission photons by the energetic free-falling electrons onto the NS or by the hybrid electrons in the boundary layer between the NS and the accretion disk could be responsible for the hard X-ray tails of Sco X-1 on the HB and NB, but neither of the two mechanisms can be responsible for the hard X-ray tail on the FB. Some possible origins for the peculiar hard X-ray tail of FB are argued.
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