Related papers: Black Hole or MECO? Decided by a Thin Luminous Rin…

In this manuscript, a 6.4yr optical quasi-periodic oscillations (QPOs) is detected in the quasar SDSS J075217.84+193542.2 (=\obj) at a redshift 0.117, of which 13.6yr-long light curve from CSS and ASAS-SN directly described by a sinusoidal…

The light curves of the two images of the double quasar Q0957+561 as obtained by Kundic et al. (1997) are almost identical, except for an overall time delay and scaling factor. This allows us to put limits on the amount of microlensing that…

In the near future, wide field surveys will discover 1000's of new strongly lensed quasars, and these will be monitored with unprecedented cadence by the Legacy Survey of Space and Time (LSST). Many of these will undergo caustic-crossing…

Q0957+561 was the first discovered gravitationally lensed quasar. The mirage shows two images of a radio-loud quasar at redshift z = 1.41. The time lag between these two images is well established around one year. We detected a very…

We show how direct microlensing-reverberation analysis performed on two well-known Quasars (Q2237 - The Einstein Cross and Q0957 - The Twin) can be used to observe the inner structure of two quasars which are in significantly different…

It has been argued in a number of recent papers that dark matter is in the form of Jupiter mass primordial black holes which betray their presence by microlensing quasars. This lensing accounts for a number of characteristic properties of…

Recent studies of black holes in the nuclei of both active and normal galaxies have yielded relationships that permit a physical interpretation of the principal components of the spectra of QSOs. It is shown that principal component (or…

We map substructure in three strong lensing systems having particularly good image data: the galaxy lens MG J0414+053 and the clusters SDSS J1004+411 and ACO 1689. Our method is to first reconstruct the lens as a pixelated mass map and then…

We investigate the photon sphere and the extremal stable circular orbit (ESCO) for massive particles over a recently proposed regular black holes with sub-Planckian curvature and Minkowskian core. We derive the effective potential for…

Sub-parsec binary massive black holes (BBHs) are long anticipated to exist in many QSOs but remain observationally elusive. In this paper, we propose a novel method to probe sub-parsec BBHs through microlensing of lensed QSOs. If a QSO…

The Event Horizon Telescope (EHT) collaboration has recently released the first image of a black hole (BH), opening a new window onto tests of general relativity in the strong field regime. In this paper, we derive constraints on the nature…

The detailed workings of the central engines of powerful quasars remain a mystery. This is primarily due to the fact that, at their cosmological distances, the inner regions of these quasars are spatially unresolvable. Reverberation mapping…

Powered by supermassive black holes at their centers, quasars are among the most luminous objects in the Universe, serving as important probes of cosmic history and galaxy evolution. The size of the accretion disc surrounding the black hole…

We present an analysis of infrared/optical/ultraviolet spectra of the two images of the first gravitationally lensed quasar Q0957+561A, B. The Hubble Space Telescope observations of Q0957+561A and Q0957+561B are separated in time by the…

We report the results of a multi-year spectroscopic and photometric monitoring campaign of two luminous quasars, PG~0923+201 and PG~1001+291, both located at the high-luminosity end of the broad-line region (BLR) size-luminosity relation…

We intend to use the impact of microlensing on the Fe III emission line blend along with a measure of its gravitational redshift to estimate the mass of the quasar's central supermassive black hole (SMBH). We fit the Fe III feature in…

The measurements of quasi-periodic oscillations (QPOs) provide a quite powerful tool to test the nature of astrophysical black hole candidates in the strong gravitational field regime. In this paper, we use QPOs within the relativistic…

In previous work we have developed a general relativistic, magnetospheric eternally collapsing object (MECO) model for black hole candidates and shown that the model is consistent with broad band spectral and luminosity characteristics and…

In this letter, deep radio observations of the quasar PKS 0743$-$67 are presented that reveal a central engine capable of driving jets with enormous kinetic luminosity, $Q>4.1 \times 10^{46}\mathrm{ergs/s}$. This result is significant…

Simulated images of a black hole surrounded by optically thin emission typically display two main features: a central brightness depression and a narrow, bright "photon ring" consisting of strongly lensed images superposed on top of the…