标题： SgrA*多频耀斑的物理起源和时间延迟 显示英文标题

标题： The Physical Origin and Time Lag of Multi-Frequency Flares from SgrA*

摘要： 射手座A$^*$，位于我们星系中心的超大质量黑洞，在各种波长上表现出耀斑，但其起源仍然神秘。 我们进行了三维双温度广义相对论磁流体动力学（GRMHD）模拟，模拟了从多环磁场配置初始化的磁化吸积流，并在旋转黑洞上进行了广义相对论辐射传输（GRRT）计算，考虑了热和非热同步辐射发射过程的贡献。 我们的结果表明，在非热辐射的帮助下，多环磁场配置的极性反转事件可以产生与观测一致的$138\,\rm THz$耀斑。 通过追踪GRRT计算中光线强度的变化，我们确定了耀斑区域的精确位置，并确认其来源于大规模的极性反转事件。 我们观察到不同频率之间的时延，由于盘中的等离子体自吸收，低频射电耀斑滞后于高频。 近红外和43 GHz耀斑之间的时延可达$\sim 50$分钟，在此期间，耀斑区域逐渐向外移动，变得在较低频率下可见。 我们的研究证实，在具有多环初始磁场配置的标准和正常演化（SANE）吸积流中，大规模的极性反转可能是驱动Sgr~A$^*$耀斑的潜在机制。 显示英文摘要

摘要： Sagittarius~A$^*$, the supermassive black hole at the center of our galaxy, exhibits flares across various wavelengths, yet their origins remain elusive. We performed 3D two-temperature General Relativistic Magnetohydrodynamic (GRMHD) simulations of magnetized accretion flows initialized from multi-loop magnetic field configuration onto a rotating black hole and conducted General Relativistic Radiative Transfer (GRRT) calculations considering contributions from both thermal and non-thermal synchrotron emission processes. Our results indicate that the polarity inversion events from the multi-loop magnetic field configurations can generate $138\,\rm THz$ flares consistent with observations with the help of non-thermal emission. By tracing the intensity evolution of light rays in GRRT calculations, we identify the precise location of the flaring region and confirm that it originates from a large-scale polarity inversion event. We observe time delays between different frequencies, with lower-frequency radio flares lagging behind higher frequencies due to plasma self-absorption in the disk. The time delay between near-infrared and 43 GHz flares can reach up to $\sim 50$ min, during which the flaring region gradually shifts outward, becoming visible at lower frequencies. Our study confirms that large-scale polarity inversion in a Standard And Normal Evolution (SANE) accretion flow with a multi-loop initial magnetic configuration can be a potential mechanism driving flares from Sgr~A$^*$.