In this study, we develop a numerical method to generate images on an observer's screen, formed by radiation from hotspots on any timelike orbits outside a black hole. This method uses the calculation of fractional numbers, enabling us not only to produce the overall image but also to distinguish between primary, secondary, and higher-order images. Building upon this, we compute the images of hotspots from eight potential types of geodesic timelike orbits outside a Kerr black hole, summarizing the properties of both the overall and individual order images. Furthermore, we calculate the centroid motion and lightcurve. Notably, we observe flare phenomena across all orbit types and classify these flares into three categories based on the Doppler and gravitational redshift effects.
Hotspot Images from Magnetic Reconnection Processes in the plunging Region of a Kerr Black Hole
College of Physics and Optoelectronic Engineering, Chongqing Normal University（重庆师范大学物理与光电工程学院）；Department of physics, college of computer science and electronic information engineering, Chongqing Technology and Business University（重庆工商大学计算机科学与电子信息工程学院物理学系）；School of Material Science and Engineering, Chongqing Jiaotong University（重庆交通大学材料科学与工程学院）
We have now entered the new era of high-resolution imaging astronomy with the beginning of the Event Horizon Telescope (EHT). The EHT can resolve the dynamics of matter in the immediate vicinity around black holes at and below the horizon scale. One of the candidate black holes, Sagittarius A* flares 1\-4 times a day depending on the wavelength. A possible interpretation of these flares could be hotspots generated through magnetic reconnection events in the accretion flow. In this paper, we construct a semi-analytical model for hotspots that include the effects of shearing as a spot moves alon…
Autocorrelation in black hole flare movies: Departures from Kerr
Institute of Fundamental Physics and Quantum Technology, and School of Physical Science and Technology, Ningbo University（宁波大学基础物理与量子技术研究所和物理科学与技术学院）；Zhejiang Key Laboratory of Extreme Universe, and BINGO Center, Ningbo University（宁波大学浙江极端宇宙重点实验室和BINGO中心）；School of Physics, and Center for High Energy Physics, Peking University（北京大学物理学院和高能物理研究中心）
Gravitational lensing near a black hole is strong enough that light rays can circle the event horizon multiple times. Photons emitted in multiple directions at a single event, perhaps because of localized, impulsive heating of accreting plasma, take multiple paths to a distant observer. In the Kerr geometry, each path is associated with a distinct light travel time and a distinct arrival location in the image plane, producing black hole glimmer. This sequence of arrival times and locations uniquely encodes the mass and spin of the black hole and can be understood in terms of properties of boun…
Short timescale variability is often associated with a black hole system. The consequence of an electromagnetic outflow suddenly generated near a Kerr black hole is considered assuming that it is described by a solution of a force-free field with a null electric current. We compute charged particle acceleration induced by the burst field. The interaction between the particle and the field is characterized by a large dimensionless number. We show that the particle is instantaneously accelerated to the relativistic regime by the field with a very large amplitude. The typical maximum energy attai…
We investigate the dynamics and emission of a starved magnetospheric region (gap) formed in the vicinity of a Kerr black hole horizon, using a new, fully general relativistic particle-in-cell code that implements Monte Carlo methods to compute gamma-ray emission and pair production through the interaction of pairs and gamma rays with soft photons emitted by the accretion flow. It is found that when the Thomson length for collision with disk photons exceeds the gap width, screening of the gap occurs through low-amplitude, rapid plasma oscillations that produce self-sustained pair cascades, with…
We develop a simple toy model for polarized images of synchrotron emission from an equatorial source around a Kerr black hole by using a semi-analytic solution of the null geodesic equation and conservation of the Penrose-Walker constant. Our model is an extension of Narayan et al. (2021), which presented results for a Schwarzschild black hole, including a fully analytic approximation. Our model includes an arbitrary observer inclination, black hole spin, local boost, and local magnetic field configuration. We study the geometric effects of black hole spin on photon parallel transport and isol…
Influence of quantum decoherence on black hole shadow visibility and time domain echoes
College of Physics and Optoelectronic Engineering, Chongqing Normal University（重庆师范大学物理与电子工程学院）；School of Big Data and Artificial Intelligence, Fuyang University of Technology（阜阳工业大学大数据与人工智能学院）；Universidade Federal de Campina Grande（坎皮纳格兰德联邦大学）；Instituto de Física, Universidade de São Paulo（圣保罗大学物理研究所）；Center for Gravitational Wave Experiment, National Microgravity Laboratory, Institute of Mechanics, Chinese Academy of Sciences（中国科学院力学研究所微重力国家实验室引力波实验中心）
