克尔时空中恒星潮汐 disruption 的广义相对论流体动力学：方法、验证与首次应用
General relativistic hydrodynamics of stellar tidal disruptions in Kerr spacetime: methods, validation, and first applications
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中文总结 AI 辅助
该研究开发了适配克尔度规的 SPHINCS 代码，通过18组恒星潮汐 disruption 模拟，明确了冲击强度和黑洞自旋对恒星结构、质量回落率的影响，验证了代码的可靠性。
中文摘要 AI 辅助
超大质量黑洞的潮汐场对恒星的 disruption 可提供关于休眠及其他难以研究的星系核的见解。最先进的数值工具尚未就可能旋转的黑洞对恒星 disruption 中强相对论效应的重要性达成一致。我们提出了一种专用数值工具，用于在弯曲时空中进行恒星潮汐 disruption 的全局流体动力学模拟。我们量化了冲击强度和黑洞自旋对恒星结构及质量回落率的作用。我们对 SPHINCS_BSSN 代码进行了适配，以开展克尔度规下恒星潮汐 disruption 的广义相对论光滑粒子流体动力学（GRSPH）模拟。我们将该代码与牛顿自引力模块耦合，并添加了熵演化公式选项以处理数值上具有挑战性的情况。除了描述实现方式和代码验证外，我们还展示了一组共18个恒星多方球的抛物线潮汐 disruption 模拟，以研究冲击强度和黑洞自旋的影响。我们证明 SPHINCS 能够执行 GRSPH 模拟，以机器精度重现基准测试。我们的恒星潮汐 disruption 模拟显示，回落率与最先进的建模结果一致。深事件会形成自引力不起作用的结构，质量回落率峰值较低，且上升至峰值的时间尺度随冲击强度降低。在这些情况下，黑洞自旋会显著影响这些量，顺行（逆行）自旋会使回落率峰值和上升至峰值的时间尺度增加（减少）。最后，在长时间尺度上，回落率倾向于以特征 t^(-5/3) 衰减。结果表明，SPHINCS 能够在合理的计算时间内对克尔度规下的高分辨率恒星潮汐 disruption 进行模拟。
英文摘要
The disruption of a star by the tidal field of a super-massive black hole may provide insights into dormant and otherwise hard-to-study galactic nuclei. State-of-the-art numerical tools have not converged on the importance of the strong relativistic effects in the disruption of stars by potentially spinning black holes. We present a specialised numerical tool to perform global hydrodynamic simulations of stellar tidal disruptions in curved spacetimes. We quantify the role of impact strength and black hole spin onto the stellar structures and mass fallback rates. We adapted the code SPHINCS_BSSN to perform General Relativistic Smoothed-Particle Hydrodynamics (GRSPH) simulations of stellar tidal disruptions in Kerr metric. We coupled the code with a Newtonian self-gravity module, and we added the option to use an entropy evolution formulation to handle numerically challenging situations. Besides describing the implementation and code validation, we present a set of 18 simulations of parabolic tidal disruptions of stellar polytropes to investigate the effect of impact strength and black hole spin. We demonstrate that SPHINCS is capable of performing GRSPH simulations, reproducing benchmark tests to machine precision. Our stellar tidal disruption simulations show that the fallback rates agree with state-of-the-art modelling. Deep events result into structures where self-gravity plays no role, the mass fallback rates peak at lower values, and rise-to-peak timescales decrease with impact strength. In these cases the black hole spin affects noticeable these quantities increasing (decrease) both fallback rate peak and rise-to-peak timescale for prograde (retrograde) spin. Last, fallback rates tend to decay with the characteristic $t^{-5/3}$ on long timescales. The results show that SPHINCS can simulate high-resolution stellar tidal disruptions in Kerr metric at a reasonable computational time.
