发表机构
Johns Hopkins University; University of Pennsylvania; NASA Goddard Space Flight Center（约翰斯·霍普金斯大学; 宾夕法尼亚大学; 美国国家航空航天局戈达德太空飞行中心）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文通过HARM3D模拟后处理，研究分离度20M的双SMBH系统的热与非热辐射，发现软X射线占比约40%，X射线连续谱与Fe Kα等效宽度呈同周期相位差约π/2的变化。
AI 中文摘要
寻找超大质量黑洞（SMBH）双星系统的电磁信号是多信使天体物理学的基石之一，它可通过脉冲星计时阵列和LISA补充这类系统的引力波观测。尽管已开展大量模拟以理解吸积双SMBH系统的热光度时变，但光谱预测相对较少，且均未超出简单发射模型范畴。本文对一个分离度为20M、以0.01爱丁顿率吸积的双星的HARM3D模拟快照进行后处理。针对黑洞质量为10^6、10^7和10^8 M☉的情况，我们基于时稳辐射转移、热平衡和电离平衡自洽求解辐射光谱，包含所有相关相对论效应及发射、吸收过程。尽管大部分热光度由盘热辐射产生，但双星四极矩排空的低密度区域产生大量X射线，观测到的光度中约40%为软X射线幂律（Γ=2.3）。我们识别出两种观测到的方位变化模式：X射线连续谱因盘中螺旋激波气体温度的固有不对称性变化约10%；当视线被团块部分遮挡内盘时，Fe Kα等效宽度下降约25%。这两种效应周期相同，相位差约π/2；对于典型活动星系核（AGN）质量和20M分离度，该周期为天量级到周量级。
英文摘要
The search for electromagnetic signals from supermassive black hole (SMBH) binary systems is one of the cornerstones of multi-messenger astrophysics, complementing gravitational wave observations of such systems by pulsar timing arrays and LISA. Although extensive simulations have been run to understand the time variability of the bolometric luminosity from accreting binary SMBH systems, comparatively few spectral predictions have been made, and none that go beyond simple emission models. In this paper, we post-process a \texttt{HARM3D} simulation snapshot of a binary at $20 M$ separation accreting at 0.01 Eddington. For black hole masses $10^6$, $10^7$, and $10^8\, M_\odot$, we self-consistently solve for the radiated spectrum on the basis of time-steady radiation transfer, thermal balance, and ionization equilibrium, including all relevant relativistic effects as well as emission and absorption processes. Although most of the bolometric luminosity is radiated thermally by the disk, the low density regions evacuated by the binary's quadrupole moment produce copious X-rays, with $\sim40\%$ of the observed luminosity in a soft X-ray power law ($Γ= 2.3$). We identify two modes of observed azimuthal variation. The X-ray continuum varies by $\sim10\%$ due to an underlying asymmetry in the gas temperature of spiral shocks in the disk. The Fe~K$α$ equivalent width dips by $\sim25\%$ when the line of sight to the inner disk is partially obscured by the lump. These two effects share the same period and are $\sim π/2$ out of phase; the period is order days to weeks for typical AGN masses and a 20$M$ separation.
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