发表机构
Graduate School of Science and Engineering, University of Toyama; Institute for Space-Earth Environmental Research (ISEE), Nagoya University（富山大学理工学研究科; 名古屋大学地球宇宙环境研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
通过分析多个黑洞双星的X射线数据，发现吸积盘内半径快速收缩至最内稳定圆轨道可预示喷流抛射，据此提出监测该半径以预报喷流时机的“喷流预报”方法。
AI 中文摘要
银河系黑洞双星XTE J1859+226的射电至软γ射线数据表明，当吸积盘内半径（$R_{\rm in}$）快速接近最内稳定圆轨道（ISCO）时，会发射离散喷流。鉴于X射线分数变振幅（rms）、$R_{\rm in}$和X射线硬度之间的相关性，先前与喷流抛射相关的现象学发现（“喷流线”和rms的急剧下降）也表明，$R_{\rm in}$快速收缩至ISCO会触发喷流形成。为了明确这些特性在其他天体中的表现，我们研究了XTE J1550-564、GX 339-4和MAXI J1820+070的X射线和射电数据。我们发现，所有四个源在喷流活动前1-10天均表现出$R_{\rm in}$和rms的下降，并且在喷流抛射之前没有出现吸积率的巨大跳跃。XTE J1859和MAXI J1820在亚爱丁顿吸积下表现出喷流活动。需要增强$\dot{M}$或超爱丁顿吸积率的喷流产生模型不太可能。多个源共有的另一个行为是rms-$R_{\rm in}$相关性的弯曲形状。因此，监测$R_{\rm in}$似乎适合预测喷流抛射的时机。当$R_{\rm in}$和rms持续下降且$R_{\rm in}$即将达到ISCO时，可以发出“喷流预报”警报，以触发目标机会观测。
英文摘要
The radio -- soft $γ$-ray data of the Galactic black hole binary XTE J1859+226 showed that discrete jets are launched when the inner radius of the accretion disk ($R_{\rm in}$) rapidly approaches the innermost stable circular orbit (ISCO). Given the correlations among the X-ray fractional variability amplitude (rms), $R_{\rm in}$, and the X-ray hardness, previous phenomenological findings related to jet ejections (``jet line'' and sharp drops of rms) also indicate that the rapid shrinkage of $R_{\rm in}$ down to the ISCO turns on the jet formation. In order to make clear how these properties appear in other objects, we investigated the X-ray and radio data of XTE J1550-564, GX 339-4, and MAXI J1820+070. We found that all the four sources show drops of $R_{\rm in}$ and rms 1-10 days ahead of a jet activity, and exhibit no huge jumps of the accretion rates prior to jet ejections. XTE J1859 and MAXI J1820 show the jet activities under sub-Eddington accretion. Models for the jet production that require an enhancement of $\dot{M}$ or a super-Eddington accretion rate are unlikely. Another behavior common to multiple sources is the curved shape of the rms--$R_{\rm in}$ correlation. Therefore, monitoring of $R_{\rm in}$ seems to be suitable to predict the timing of jet ejections. When both $R_{\rm in}$ and rms continuously decrease and when $R_{\rm in}$ is about to reach the ISCO, alerts can be circulated as a ``jet forecast'' for triggering Target-of-Opportunity observations.
CommentsAccepted for publication in ApJ, 12 pages, 4 figures
