Proceedings, Volume 17, Issue 1

The search for periodic signals from blazars has become an actively pursued field of research in recent years. This is because periodic signals bring us information about the processes occurring near the innermost regions of blazars, which are mostly...

The continuous X-ray flux of stellar-mass black holes provides an excellent source of data to learn about the astrophysics of accretion disks and about the spacetime itself. The extraction of information, however, depends heavily on our ability to co...

Properties of charged particle motion in the field of magnetized black holes (BHs) imply four possible regimes of behavior of ionized Keplerian disks: survival in regular epicyclic motion, transformation into chaotic toroidal state, destruction due t...

We present results regarding the disc response functions and the corresponding time lags assuming a standard Novikov–Thorne accretion disc illuminated by a point-like X-ray source. We took into account all relativistic effects in the light prop...

A compact object captured by a supermassive black hole, named as extreme-mass-ratio inspiral (EMRI), is one of the most important gravitational wave sources for low-frequency interferometers such as LISA, Taiji, and TianQin. EMRIs can be used to accu...

TV Cassiopeia (TV Cas) is a well-known eclipsing Algol-type binary comprising a B9V primary and F7 IV secondary in an orbit with a period of 1.81 days, together with a purported low-mass companion in a wide orbit. Despite the considerable attention T...

The nearby M87 hosts an exceptional relativistic jet. It has been regularly monitored in radio to TeV bands, but little has been done in hard X-rays ≳10 keV. For the first time, we have successfully detected hard X-rays up to 40 keV from its X-ray co...

X-ray time lags are complicated in nature. The exact reasons for complex lag spectra are as yet unknown. However, the hard lags, in general, are believed to be originated due to inverse Comptonization process. However, the origin of soft lags remaine...

In this paper, we briefly present RELXILL_NK, the first and currently only readily available model of the relativistic reflection spectrum of black hole accretion disks that includes non-Kerr solutions for the black hole spacetime, thus allowing for...

In this work, we obtain the deflection angle for a boosted Kerr black hole in the weak field approximation using the optics in a curved spacetime developed by J. L. Synge in 1960. We study the behavior of light in the presence of plasma by considerin...

Gravitational wave observations offer unique opportunities to probe gravity in the strong and dynamical regime, which was difficult to access previously. We here review two theory-agnostic ways to carry out tests of general relativity with gravitatio...

Gravitational waves (GWs) encode important information about the mass of the source. For binary black holes (BBHs), the templates that are used to retrieve the masses normally are developed under the assumption of a vacuum environment. However, theor...

Is there an unknown long-range force between dark matter (DM) and ordinary matters? When such a fifth force exists and in the case that it is ignored, the equivalence principle (EP) is violated apparently. The violation of EP was severely constrained...

In this paper, we review our current efforts to test General Relativity in the strong field regime by studying the reflection spectrum of supermassive black holes. So far we have analyzed 11 sources with observations of NuSTAR, Suzaku, Swift, and XMM...

The recent detections of gravitational waves from binary systems of black holes are in remarkable agreement with the predictions of General Relativity. In this pedagogical mini-review, I go through the physics of the different phases of the evolution...