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Coalescing black-hole binaries are expected to be the strongest sources of gravitational waves for ground-based interferometers as well as the space-based interferometer LISA. Recent progress in numerical relativity now makes it possible to…
Gravitational waves are rapidly becoming a very reliable tool for testing alternative theories of gravity. In particular, features in the gravitational wave emission during black hole ringdown phase provide a direct probe of the spacetime…
We briefly consider the data of collaboration LIGO/VIRGO for gravitational waves (GW) and the recent observations of Event Horizon Telescope (EHT), and we discuss difficulties for finding the right theory of gravity and the nature of the…
We study time evolution and gravitational wave emission properties of a black hole orbiting {\it inside} an accretion disk surrounding a massive black hole. We simultaneously solve the structure equations of the accretion disk in presence…
Using the Teukolsky and Sasaki-Nakamura equations for the gravitational perturbation of the Kerr spacetime, we calculate the post-Newtonian expansion of the energy and angular momentum luminosities of gravitational waves from a test…
We use data from the second science run of the LIGO gravitational-wave detectors to search for the gravitational waves from primordial black hole (PBH) binary coalescence with component masses in the range 0.2--$1.0 M_\odot$. The analysis…
Our aim in this work is to outline some physical consequences of the interaction between black holes and scalar field halos in terms of gravitational waves. In doing so, the black hole is taken as a static and spherically symmetric…
We report results of a numerical-relativity simulation for the merger of a black hole-neutron star binary with a variety of equations of state (EOSs) modeled by piecewise polytropes. We focus in particular on the dependence of the…
We produce the gravitational waveforms for the extreme mass ratio inspiral systems (EMRIs) of binary stars moving around central supermassive black hole (SBH), or called B-EMRIs. We calculate the external orbits of the binary stars via the…
Traditionlly, gravitational wave emission from a coalescing binary system is computed using point mass approximations without considering any accretion disk. However, it is believed that in many of the galactic nuclei, there are…
This is the second in a series of papers whose aim is to generate ``adiabatic'' gravitational waveforms from the inspiral of stellar-mass compact objects into massive black holes. In earlier work, we presented an accurate (2+1)D…
Using black hole perturbation theory, we calculate the gravitational waves produced by test particles moving on bound geodesic orbits about rotating black holes. The orbits we consider are generic - simultaneously eccentric and inclined.…
The metrics of gravitational shock waves for a Schwarzschild black hole in ordinary coordinates and for a Kerr black hole in Boyer-Lindquist coordinates are derived. The Kerr metric is discussed for two cases: the case of a Kerr black hole…
In this thesis, we use numerical relativity to investigate gravitational waves from binary black holes in extensions of GR. We first study spherically symmetric gravitational collapse in cubic Horndeski theories of gravity. By varying the…
The measurement of gravitational waves produced by binary black-hole mergers at the Advanced LIGO has encouraged extensive studies on the stochastic gravitational wave background. Recent studies have focused on gravitational wave sources…
Using the cross-correlation data from the first three observing runs of the LIGO-Virgo-KAGRA Collaboration, we search for a gravitational-wave background (GWB) from primordial black holes, arising from the superposition of compact binary…
Gravitational wave astronomy has opened an unprecedented window onto tests of gravity and fundamental physics in the strong-field regime. In this study, we examine a series of well-motivated deviations from the classical Kerr solution of…
The tentative Gravitational Wave Echo (GWE) at a frequency of about $72\,Hz$ has been recently claimed at $4.2\sigma$ significance level in the GW170817 event. GWEs can be used as a tool to study the characteristics of ultra-compact stellar…
A new version of the Teukolksy Master Equation, describing any massless field of different spin $s=1/2,1,3/2,2$ in the Kerr black hole, is presented here in the form of a wave equation containing additional curvature terms. These results…
We compute the gravitational waveform emitted during the transition from quasi-spherical inspiral to plunge, merger and ringdown for a system of two black holes in the extreme mass ratio limit, where the primary is spinning and the…