Related papers: Time lag in transient cosmic accreting sources
An intervening galaxy acts as a gravitational lens and produces multiple images of a single source such as a remote galaxy. Galaxies have peculiar speeds in addition to the bulk motion arising due to the expansion of the universe. There is…
We investigate the accretion disk geometry in Galactic black hole sources by measuring the time delay between soft and hard X-ray emissions. Similar to the recent discoveries of anti-correlated hard X-ray time lags in Cyg X-3 and GRS…
Here we investigate light curves of the continuum and emission lines of five type 1 active galactic nuclei (AGN) from our monitoring campaign, to test time-evolution of their time delays.Using both modeled and observed AGN light curves we…
Multiple models have been suggested over the years to explain the structure and support of accretion disks around supermassive black holes, from the standard thin thermal-pressure-dominated $\alpha$-disk model to more recent models that…
When a source of gravity waves is conveniently placed between the Earth and some source of light, preferably a pulsating source, the magnitude of time delays induced by the gravity waves could, in optimal situations, be not too far out of…
To understand the physical processes governing accretion discs we can study active galactic nuclei (AGN), X-ray binary systems (XRBs) and cataclysmic variables (CVs). It has been shown that XRBs and CVs show similar observational properties…
Black hole X-ray binaries in their hard and hard-intermediate states display hard and soft time lags between broadband noise variations (high-energy emission lagging low-energy and vice versa), which could be used to constrain the geometry…
The characteristic timescale at which the variability of active galactic nuclei (AGNs) turns from red noise to white noise can probe the accretion physics around supermassive black holes (SMBHs). A number of works have studied the…
We compile a sample of 92 active galactic nuclei (AGNs) at z<0.75 with $gri$ photometric light curves from the archival data of the Zwicky Transient Facility and measure the accretion disk sizes via continuum reverberation mapping. We…
Time variability is a strong probe of energetic phenomena which occur at small spatial scales, like Active Galactic Nuclei (AGN). We use ALMA observations at 100 GHz executed over a period of 2.5 months to look for time variability in the…
We present a Comptonization model for the observed properties of the energy-dependent soft/hard time lags and pulsed fraction (amplitude) associated with the pulsed emission of a neutron star (NS). We account for the soft lags by…
Number of monitoring observations of continuum emission from Active Galactic Nuclei (AGNs) have been made in optical--X-ray bands. The results obtained so far show (i) random up and down on timescales longer than decades, (ii) no typical…
Gas clouds are present in the Galactic centre, where they orbit around the supermassive black hole. Collisions between these clumps reduce their angular momentum, and as a result some of the clumps are set on a plunging trajectory.…
Gravitational microlensing within the Galaxy offers the prospect of probing the details of distant stellar sources, as well as revealing the distribution of compact (and potentially non-luminous) masses along the line-of-sight. Recently, it…
Sari and Piran have demonstrated that the time structure of gamma-ray bursts must reflect the time structure of their energy release. A model which satisfies this condition uses the electrodynamic emission of energy by the magnetized…
We present new evidence of X-ray absorption variability on time scales from a few hours to a few days for several nearby bright AGNs. The observed N_H variations imply that the X-ray absorber is made of clouds eclipsing the X-ray source…
Mass estimates of black holes (BHs) in the centers of Active Galactic Nuclei (AGN) often rely on the radius-luminosity relation. However, this relation, usually probed by reverberation mapping (RM), is poorly constrained in the…
The driving of turbulence in galaxies is deeply connected with the physics of feedback, star formation, outflows, accretion, and radial transport in disks. The velocity dispersion of gas in galaxies therefore offers a promising…
We derive the delay in travel time of photons due to the spin of a body both inside a rotating shell and outside a rotating body. We then show that this time delay by the spin of an astrophysical object might be detected in different images…
Accretion is an essential physical process in black-hole X-ray binaries (BHXRBs) and active galactic nuclei. The properties of accretion flows and their radiation were originally considered to be uniquely determined by the mass accretion…