601 talks across 60 sessions. Search by title, author or full text.
601 results
The quantization of gravity is widely believed to result in gravitons – particles of discrete energy that form gravitational waves. But their detection has so far been considered impossible, in particular Dyson recently analysed whether observing single gravit…
Fast radio burst (FRB) sources show a wide range of repetition rates, with some being able to emit hundreds and even thousands of bursts within hours. This provides a valuable opportunity for studying their burst morphology in detail, investigating their polar…
I will discuss the detection of exotic compact objects, such as primordial black holes, boson stars, etc, with gravitational waves from a binary system where the mass ratio is extremely small (or large), and show that such exteme mass ratio inspirals and mini-…
Unmodeled gravitational-wave signals from magnetars are expected to be weak and challenging to detect in LIGO-Virgo-KAGRA data. We introduce a new method to denoise and stack signals from repetitive magnetar bursts, such as the 2020 SGR 1935+2154 burst storm w…
We present the strategy, analysis, and results of our four-year timing program of RX J0806.4-4123 with NICER. RX J0806.4-4123 belongs to the group of radio-quiet X-ray thermal isolated neutron stars (XTINSs) that are located between the rotation-powered pulsar…
Large-scale cosmic emissions of explosive energy that occur during the explosions of certain supernovae or the merger of compact objects are called gamma-ray bursts. We study the radiation of the ultrarelativistic shell in the diffusion approximation, which ta…
The last century has seen tremendous improvements in our understanding of electromagnetism. An important discovery was made by Einstein in 1916, who combined thermodynamics and atomic physics to predict stimulated emission. The quantization of Maxwell’s Equati…
The origin of the prompt emission in gamma-ray bursts (GRBs) remains debated. Our understanding is primarily derived from wide-field telescopes that operate within the 10 keV-10 MeV range. However, capturing early emissions at higher energies (above 100 GeV) i…
Ultraluminous X-ray sources (ULXs) have captivated researchers for decades due to their exceptionally high luminosities and unique spectral characteristics. Some of these sources defy expectations by exhibiting super-Eddington luminosities with respect to stel…
Compact objects are usually described using the perfect fluid formalism. However, in astrophysical processes out of local equilibrium, dissipative effects become important to realistically describe the dynamics of the system. In this work, we present for the f…
In general relativity, the use of conformal transformation is ubiquitous and leads to two different frames of reference, known as the Jordan and the Einstein frames. Typically, the transformation from the Jordan frame to the Einstein frame involves introducing…
We examine the geometrical difference between non-extremal black hole(NXBH), extremal black hole(XBH) and naked singularity(NS) via Lense-Thirring(LT) effect in spinning modified-gravity(MOG). For NXBH, we find that the LT frequency (ΩLT ) is proportional to t…
Cosmological inflation is a popular paradigm for understanding Cosmic Microwave Background Radiation (CMBR); however, it faces many conceptual challenges. An alternative mechanism to inflation for generating an almost scale-invariant spectrum of perturbations…
Causal sets are locally finite, partially ordered sets (posets), which are considered as discrete models of spacetime. On the one hand, causal sets corresponding to a spacetime manifold are commonly generated with a random process called sprinkling. This proce…
One of the most powerful tests of our cosmological model is to verify the predicted growth of largescale structure with time. Intriguingly, many recent measurements have reported small discrepancies in such tests of structure growth (”the S8 tension”), which c…
In this work, we investigate the impact of the Dark Energy Spectroscopic Instrument (DESI) 2024 data on dark energy scenarios. Specifically, we analyze three typologies of models, the first in which the cosmic speed up is related to thermodynamics, the second…
The no-hair conjecture asserts that all black holes in general relativity (GR) coupled to any matter must be Kerr–Newman type. The three independent externally observable classical parameters— mass, electric charge, and angular momentum —uniquely determine all…
Abstract: Dust is considered to be the simplest form of matter composed of pressureless, radiation and is abundant in galaxies, clusters and superclusters in a cosmological context. It has also been shown that stars are encompassed by these radiating pressurel…
This work investigates the long-term evolution of two bodies in nearby initially coplanar orbits around a central dominant body, perturbed by a fourth body on a distant Keplerian orbit. Previous works on this setup enforced circular orbits by adding a spherica…
We develop a framework to compute the tidal response of a Kerr-like compact object in terms of its reflectivity, compactness, and spin, both in the static and the frequency-dependent case. Here we focus on the low-frequency regime, which can be solved fully an…
In our presentation, we demonstrate the spacetime properties of a monopole within nonlinear σ- models in Eddington inspired Born-Infeld gravity. Specifically, we investigate characteristic circular orbits of test particles and photons, including circular null…
The recently reported transient event ASASSN-20qc (Pasham et al., 2024), which was revealed first by the optical outburst and then the delayed soft X-ray emission, was shown to exhibit a quasiperiodic ultrafast outflow. I will show using analytical as well as…
Quasi-periodic eruptions (QPEs) are an emerging class of high amplitude bursts of X-ray radiation, repeating on a hours-day timescale, recently discovered near the central supermassive black holes (SMBHs) of a few low-mass galaxies. I will briefly review our c…
The Einstein Telescope (ET), third generation gravitational wave (GW) interferometer, will explore a large volume of the universe, detecting up to 105 binary neutron star system mergers (BNS) per year, beyond redshift z ~ 3. This will clearly revolutionize GW…
In this research, we examine the gravitational behavior of dense astronomical bodies, specifically white dwarfs and neutron stars, using Einstein’s gravitational theories. We explore the effects of deviations from spherical symmetry by applying a simplified ma…