人马座A* 的倾斜黑洞吸积盘模型：时变毫米到近红外辐射
Tilted black hole accretion disc models of Sagittarius A*: time-variable millimetre to near-infrared emission
摘要：
对银河系中心黑洞候选者Sgr A* 的高分辨率、多波长和时域观测，可以直接检验当代吸积理论。到目前为止，所有的模型都假设吸积盘和黑洞角动量轴之间是对齐的，但这对于像Sgr A* 上那样的几何厚吸积流是不合理的。相反，我们计算的图像和光谱从一组模拟的吸积流错位（“倾斜”）15度的黑洞自旋轴，并将它们与毫米（mm）近红外（NIR）观测。来自偏心流体轨道的非轴对称驻波占主导地位的排放，导致广泛的可能的图像形态。这些影响使先前通过模型拟合得到的参数估计无效，包括对无量纲黑洞自旋的估计，除非自旋或倾斜值可能较低。在1.3毫米时，图像具有新月形的形态，黑洞阴影可能仍然可以用于未来的毫米VLBI观测。冲击加热导致高能电子（T > 10^12 K），这可以自然地产生观察到的近红外通量，光谱指数和快速变化（“耀斑”）。这种近红外发射与毫米中的发射不相关，这也与观测结果一致。这些是第一个模型，自洽地解释了时间变量毫米到近红外发射的Sgr A*。该模型的预测，包括显着的结构变化与毫米VLBI观察到的动力学（小时）和透镜-Thirring岁差（日-年）的时间尺度;和30-50微弧秒的变化，质心位置从极端的引力透镜事件在近红外耀斑，未来的VLT仪器重力检测。如果观测到的近红外辐射是由倾斜的吸积盘中的激波加热引起的，那么银河系中心的黑洞就有一个正的、非零的自旋参数（a > 0）。
英文摘要：
High-resolution, multi-wavelength, and time-domain observations of the Galactic centre black hole candidate, Sgr A*, allow for a direct test of contemporary accretion theory. To date, all models have assumed alignment between the accretion disc and black hole angular momentum axes, but this is unjustified for geometrically thick accretion flows like that onto Sgr A*. Instead, we calculate images and spectra from a set of simulations of accretion flows misaligned ('tilted') by 15 degrees from the black hole spin axis and compare them with millimetre (mm) to near-infrared (NIR) observations. Non-axisymmetric standing shocks from eccentric fluid orbits dominate the emission, leading to a wide range of possible image morphologies. These effects invalidate previous parameter estimates from model fitting, including estimates of the dimensionless black hole spin, except possibly at low values of spin or tilt. At 1.3mm, the images have crescent morphologies, and the black hole shadow may still be accessible to future mm-VLBI observations. Shock heating leads to high energy electrons (T > 10^12 K), which can naturally produce the observed NIR flux, spectral index, and rapid variability ('flaring'). This NIR emission is uncorrelated with that in the mm, which also agrees with observations. These are the first models to self-consistently explain the time-variable mm to NIR emission of Sgr A*. Predictions of the model include significant structural changes observable with mm-VLBI on both the dynamical (hour) and Lense-Thirring precession (day-year) timescales; and ~30-50 microarcsecond changes in centroid position from extreme gravitational lensing events during NIR flares, detectable with the future VLT instrument GRAVITY. If the observed NIR emission is caused by shock heating in a tilted accretion disc, then the Galactic centre black hole has a positive, non-zero spin parameter (a > 0).
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
