相关论文: Forward Ray Tracing and Hot Spots in Kerr Spacetim…
The efforts to probe the horizon-scale structure of black holes, such as Event Horizon Telescope and GRAVITY interferometer, might provide valuable insights into the strong-field regime of Einstein's theory of gravity. In the near field…
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…
We extract elegant and concise analytic formulae for the mass and rotation parameters of the Kerr black hole as well as its distance from the Earth only in terms of directly measurable quantities of the accretion disk revolving in the black…
General relativity makes clear predictions about the spacetime geometry around black holes. In the near future, new facilities will have the capability to explore the metric around SgrA$^*$, the supermassive black hole candidate at the…
The images of supermassive black holes surrounded by optically-thin, radiatively-inefficient accretion flows, like those observed with the Event Horizon Telescope, are characterized by a bright ring of emission surrounding the black-hole…
This Thesis describes the basic framework and applications of a relativistic ray-tracing code for analyzing accretion processes around Kerr black holes. We begin in Chapter 1 with a brief historical summary of the major advances in black…
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…
The Kerr spacetime is one of the most widely known solutions to Einstein's vacuum field equations and is commonly used to describe a black hole with mass $m$ and spin $a$. Astrophysical observations in the electromagnetic spectrum as well…
Intense flaring events in the near-infrared and X-ray wavebands of our Galactic Center have been the subject of research for decades. In recent years, the GRAVITY instrument of the Very Large Telescope captured the motion and polarimetric…
We model the light-curves from radiation-driven clouds near an accreting black hole. Taking into account the multiple images due to strong gravitational lensing, we find that sharp spikes can significantly enhance the observed flux.…
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…
Sub milli-arcsecond astrometry and imaging of the black hole Sgr A* at the Galactic centre may become possible in the near future at infrared and sub-millimetre wavelengths. Motivated by observations of short-term infrared and X-ray…
Light passing near a black hole can follow multiple paths from an emission source to an observer due to strong gravitational lensing. Photons following different paths take different amounts of time to reach the observer, which produces an…
The strong gravitational field of a black hole bends light, forming multi-level images, yet extracting precise spacetime information from them remains challenging. In this study, we investigate how gravitational lensing leaves unique and…
Ongoing astronomical efforts extract physical properties of black holes from electromagnetic emissions in their near-vicinity. This requires finding the null geodesics which extend from the near-horizon region out to a distant observatory.…
Future X-ray instrumentation is expected to allow us to significantly improve the constraints derivedfrom the Fe K lines in AGN, such as the black-hole angular momentum (spin) and the inclination angle of the putative accretion disk. We…
Interpreting horizon-scale observations of astrophysical black holes demands a general understanding of null geodesics in the Kerr spacetime. These may be divided into two classes: "direct" rays that primarily determine the observational…
In at least two black hole binary systems, the Rossi X-Ray Timing Explorer has detected high frequency quasi-periodic oscillations (HFQPOs) with a 2:3 frequency commensurability. We propose a simple hot spot model to explain the positions,…
Using the Kerr-Schild formalism to solve the Einstein-Maxwell equations, we study energy transport due to time-dependent electromagnetic perturbations around a Kerr black hole, which may work as a mechanism to illuminate a disk located on…
The spatiotemporal content of a black-hole movie is set jointly by source variability and by the distribution of light-travel times across the image. In the slow-light prescription, an image evaluated at fixed observer time contains photons…