采用Rezzolla-Zhidenko时空的GRMHD模拟中的黑洞吸积与辐射变异性
Black hole accretion and radiation variability in GRMHD simulations with Rezzolla-Zhidenko spacetime
AI总结：
本研究利用Rezzolla-Zhidenko时空的二维GRMHD模拟，探究偏离广义相对论的球对称黑洞时空中的吸积动力学与230GHz辐射涨落特性，发现偏离参数与光变幅度系统性相关，为区分Sgr A*的黑洞解提供新途径。
摘要：
事件视界望远镜（EHT）已揭示了我们银河系中心的超大质量黑洞人马座A*（Sgr A*）的视界尺度辐射，为检验引力理论提供了新平台。下一步工作涉及利用EHT时间变异性数据和广义相对论磁流体动力学（GRMHD）模拟研究黑洞附近的吸积流与时空结构。我们采用Rezzolla-Zhidenko时空的二维GRMHD模拟，研究了偏离广义相对论的球对称黑洞时空中的吸积动力学。本研究基于弱引力场约束和Sgr A*的阴影尺寸，系统探究了非克尔GRMHD模拟得到的光变曲线变幅如何依赖于对施瓦西时空的偏离程度。我们发现吸积流的动力学特性系统性地依赖于该偏离程度。在引力势更深的时空中，流体速度和阿尔芬速度相对于施瓦西度规持续降低，表明动力学行为更弱。我们还通过广义相对论辐射转移模拟计算230 GHz处的光度涨落，检验了时空偏离对辐射特性的影响，该计算与EHT观测结果一致。这些涨落的幅度表现出对偏离参数的系统性依赖：与施瓦西度规相比，引力势越深，涨落幅度越小。我们使用理论预测的度规之一——描述非奇异黑洞的Hayward度规——验证了这些特征。预计该特性在未来纳入更真实吸积盘模型和电子冷却的全面模拟中会产生类似效应，有望助力区分可解释Sgr A*变异性的黑洞解。
英文摘要：
The Event Horizon Telescope (EHT) has revealed the horizon-scale radiation of Sagittarius A* (Sgr A*), our galaxy's central supermassive black hole, offering a new platform to test gravitational theories. The next step involves studying accretion flows and spacetime structures near black holes using EHT time variability data and GRMHD simulations. We study accretion dynamics in spherically symmetric black hole spacetimes deviating from general relativity, using 2D GRMHD simulations with Rezzolla-Zhidenko spacetime. This study systematically investigates how light curve variability amplitudes from non-Kerr GRMHD simulations depend on Schwarzschild spacetime deviations, based on the constraints from weak gravitational fields and Sgr A*'s shadow size. We find that the dynamics of accretion flows systematically depend on the deviation. In spacetimes with a deeper gravitational potential, fluid and Alfvén velocities consistently decrease relative to the Schwarzschild metric, indicating weaker dynamical behavior. We also examine the influence of spacetime deviations on radiation properties by computing luminosity fluctuations at 230 GHz using general relativistic radiative transfer simulations, in line with EHT observations. The amplitude of these fluctuations exhibits a systematic dependence on the deviation parameters, decreasing for deeper gravitational potentials compared to the Schwarzschild metric. These features are validated using one of the theoretically predicted metrics, the Hayward metric, a model that describes nonsingular black holes. This characteristic is expected to have similar effects in future comprehensive simulations that include more realistic accretion disk models and electron cooling in the future, potentially aiding in distinguishing black hole solutions that explain the variability of Sgr A*.
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