Related papers: The Accretion Disc-Jet Connection in Blazars
We propose a simple dynamical model that may account for the observed spectral and temporal properties of GRS 1915+105 and XTE J1550-5634. The model is based on the assumption that a fraction of the radiation emitted by a hot spot lying on…
Episodic jets are usually observed in the intermediate state of black hole transients during their X-ray outbursts. Here we report the discovery of a strong positive correlation between the peak radio power of the episodic jet $P_{\rm jet}$…
Black-hole driven relativistic astrophysical jets, such as blazars and gamma-ray bursts (GRBs), are powerful sources of electromagnetic radiation. Their emission is powered by some energy dissipation and particle acceleration mechanism…
The fundamental plane for black hole activity constitutes a tight correlation between jet power, X-ray luminosity, and black hole mass. Under the assumption that a Blandford-Znajek-type mechanism, which relies on black hole spin,…
Blazar jet structure can be indirectly resolved by analyzing the multiwavelength variability. In this work, we analyze the long-term variability of blazars in radio, optical and X-ray energies with the Gaussian process (GP) method. The…
Accretion discs are present around both stellar-mass black holes in X-ray binaries and supermassive black holes in active galactic nuclei. A wide variety of circumstantial evidence implies that many of these discs are warped. The standard…
We analyze X-ray light curves of the blazars Mrk 421, PKS 2155-304, and 3C 273 using observations by the Soft X-ray Telescope on board AstroSat and archival XMM-Newton data. We use light curves of length 30-90 ks each from 3-4 epochs for…
Our understanding of the unification of jetted AGN has evolved greatly as jet samples have increased in size. Here, based on the largest-ever sample of over 2000 well-sampled jet spectral energy distributions, we examine the synchrotron…
We study the X-ray variability properties of distant AGNs in the Chandra Deep Field-South region over 17 years, up to $z\sim 4$, and compare them with those predicted by models based on local samples. We use the results of Monte Carlo…
Several properties of the standard alpha-disc model for active galactic nuclei (AGN) are not entirely consistent with AGN observations. As well as such discrepencies, observations show evidence for the existence of high mass outflow winds…
X-ray inter-band time lags are observed during the outbursts of black hole X-ray binaries (BHXRBs). Timing analysis of fast variability in low Fourier frequency bands shows that high-energy photons lag behind low-energy photons, a…
Recurring outbursts associated with matter flowing onto compact stellar remnants (black-holes, neutron stars, white dwarfs) in close binary systems, provide strong test beds for constraining the poorly understood accretion process. The…
We develop the power spectral density (PSD) model to explain the nature of the X-ray variability in IRAS 13224-3809, including the full effects of the X-ray reverberation due to the lamp-post source. We utilize 16 XMM-Newton observations…
We consider the broadband spectral energy distribution of the high energy peaked (HBL) blazar Mkn 501 using $\textit{Swift}$-XRT/UVOT, NuSTAR and $\textit{Fermi}$-LAT observations taken between 2013 and 2022. The spectra were fitted with a…
The three X-ray states of active accretion in black-hole binaries have been re-defined to focus attention on different physical elements that may contribute radiation: the accretion disk, a jet, and a compact and radio-quiet corona.…
We study the outbursts of the black hole X-ray binaries MAXI J1659-152, SWIFT J1753.5--0127 and GX 339-4 with the Swift X-ray Telescope. The bandpass of the X-ray Telescope has access to emission from both components of the accretion flow:…
The X-ray spectra of black hole binaries in the low/hard state first harden as the flux decreases, then soften. This change in behaviour has been variously attributed to either the X-rays switching from being produced in the flow to being…
We simulate the viscous evolution of an accretion disc around a spinning black hole. In general any such disc is misaligned, and warped by the Lense-Thirring effect. Unlike previous studies we use effective viscosities constrained to be…
Blazars, a class of active galactic nuclei (AGN) powered by supermassive black holes, are known for their remarkable variability across multiple timescales and wavelengths. Despite significant advancements in our understanding of AGN…
Black holes are the simplest possible objects, characterised by only mass and spin. We see them via accretion, so there is one more fundamental parameter which is the mass accretion rate. Here I will review how the data from both stellar…