With the recent release of the black hole image of Sgr A* alongside the earlier image of M87*, one can achieve an in-depth understanding of gravitational physics at the horizon scale. According to the Event Horizon Telescope (EHT) collaboration, the observed image is consistent with the expected appearance of a Kerr black hole. In the present work, we consider Kerr-Newman black holes in Weyl-Cartan theory as a supermassive black hole (BH) and evaluate the parameters of the model with shadow size estimates done by the observations of M87* and Sgr A* from EHT. Such a study can be a possible way to distinguish Weyl-Cartan theory from general relativity and ensure the validity of the idea. Besides, we calculate the energy emission rate for the corresponding BH and discuss how the model's parameters affect the emission of particles around the black hole. With this investigation, we are able to examine the time evolution and lifetime of the black hole in such a theory of gravity.
Probing Kalb-Ramond gravity with charged rotating black holes: constraints from EHT observations
Centre for Theoretical Physics, Jamia Millia Islamia（贾米阿米利亚伊斯兰大学理论物理中心）；Institute for Theoretical Physics and Cosmology, Zhejiang University of Technology（浙江工业大学理论与宇宙学研究所）；Astrophysics and Cosmology Research Unit, School of Mathematics, Statistics and Computer Science, University of KwaZulu-Natal（夸祖鲁-纳塔尔大学数学、统计与计算机科学学院天体物理学与宇宙学研究组）
New analytical model of rotating black hole with dark matter halo: constraints from EHT observations and accretion disk
Harbin Institute of Technology（哈尔滨工业大学）；New Uzbekistan University（新乌兹别克斯坦大学）；Tashkent University of Applied Sciences（塔什干应用科学大学）；National Research University TIIAME（国家研究型大学TIIAME）；Zhejiang University of Technology（浙江工业大学）；Tashkent State Technical University（塔什干国立技术大学）；National University of Uzbekistan（乌兹别克斯坦国立大学）
Stationary scalar clouds, quasinormal ringing, and observational signatures of (near-)extremal rotating Kalb-Ramond black holes: from the superradiant threshold to EHT bounds
Cyprus International University（塞浦路斯国际大学）；Eastern Mediterranean University（东地中海大学）
Shadow of rotating black hole surrounded by dark matter
School of Physics and Electronic Engineering, Shanxi Normal University（山西师范大学物理与电子工程学院）；College of Physics, Guizhou University（贵州大学物理学院）；College of Physical Science and Technology, Hebei University（河北大学物理科学与技术学院）
Shadow and Quasinormal Modes of a Rotating Loop Quantum Black Hole
In this paper, we construct an effective rotating loop quantum black hole (LQBH) solution, starting from the spherical symmetric LQBH by applying the Newman-Janis algorithm modified by Azreg-Aïnou's non-complexification procedure, and study the effects of loop quantum gravity { (LQG) on its shadow}. Given the rotating {LQBH}, we discuss its horizon, ergosurface, and regularity {as} $r \to 0$ . Depending on the values of the specific angular momentum $a$ and the polymeric function $P$ arising from {LQG}, we {find} that the rotating solution we obtained can represent a regular black hole , a reg…
Modelling the Sgr A* Black Hole Immersed in a Dark Matter Spike
研究了银河系中心黑洞Sgr A * 附近的暗物质尖峰效应。我们的主要目标是调查目前和未来的天文观测的Sgr A * 是否可以检测到这样的DM尖峰的存在。首先，我们构造了一个静态球对称黑洞周围的时空度规，然后利用Newman-Janis-Azreg Aïnou算法将这个解推广到旋转黑洞。对于静态BH度规，我们使用的数据的S2星绕Sgr A * 确定和分析的两个自由参数的约束特征的密度和最内边界的DM晕周围的BH。此外，利用银河系中已有的DM尖峰密度$ρ_\text{sp}$和DM尖峰半径$R_\text{sp}$的观测数据，我们考虑了围绕Sgr A * BH的几何厚度的吸积盘模型，并证明了DM分布对BH阴影半径和像的影响在实际DM密度下是相当微弱的.仅当DM密度在BH附近为$ρ_\text{sp} \sim (10^{-19}-10^{-20})$ g/cm $^3$数量级时才变得显著。我们进一步分析了用无线电干涉测量法观察这种效应的可能性，用类似EHT的阵列模拟观察，发现在不久的将来不太可能检测到这种效应。
