Related papers: Modelling absorption and emission profiles from ac…
Accretion discs in strong gravity ubiquitously produce winds, seen as blueshifted absorption lines in the X-ray band of both stellar mass X-ray binaries (black holes and neutron stars), and supermassive black holes. Some of the most…
We present the analysis of seven \emph{Chandra} High Energy Transmission Grating Spectrometer and six simultaneous \emph{RXTE} Proportional Counter Array observations of the persistent neutron star (NS) low-mass X-ray binary GX 13+1 on its…
We have studied several neutron star high-mass X-ray binaries (HMXBs) with super-giant (SG) companions using a wind-fed binary model associated with the magnetic field. By using the concept of torque balance, the magnetic field parameter…
Using two-dimensional radiation hydrodynamic simulations, we investigate origin of the ultra fast outflows (UFOs) that are often observed in luminous active galactic nuclei (AGNs). We found that the radiation force due to the spectral lines…
In some radio-quiet active galaxies (AGN), high-energy absorption features in the x-ray spectra have been interpreted as Ultrafast Outflows (UFOs) -- highly ionised material (e.g. Fe XXV and Fe XXVI) ejected at mildly relativistic…
Variable X-ray absorption has been observed in active galactic nuclei (AGN) on several time scales. Observations allow us to identify the absorber with clouds associated either with the clumpy torus (parsec scales, long timescales) or with…
We use a combination of radiation hydrodynamics (rad-HD) and photoionization modeling to study line-driven disc winds for a range of black hole masses. We refined previous models by incorporating heating, cooling, and radiation forces from…
Multiple spectroscopic lines of different elements observed in winds from X-ray binaries (XRBs), based on one zone model, indicate super-solar abundance of elements, e.g. Mg, Si, S, Ar, Ca, Cr, Mn, Co. The one zone model considers similar…
Continuing our study of the role and evolution of accretion disc winds in the microquasar GRS 1915+105, we present high-resolution spectral variability analysis of the beta and gamma states with the Chandra High Energy Transmission Grating…
Wind-fed models offer a unique way to form predictive models of the accretion flow surrounding Sagittarius A*. We present 3D, wind-fed MHD and GRMHD simulations spanning the entire dynamic range of accretion from parsec scales to the event…
Ultraviolet (UV) line driven winds may be an important part of the active galactic nucleus (AGN) feedback process, but understanding their impact is hindered by the complex nature of the radiation hydrodynamics. Instead, we have taken the…
Protostellar discs play an important role in star formation, acting as the primary mass reservoir for accretion onto young stars and regulating the extent to which angular momentum and gas is released back into stellar nurseries through the…
We discuss a model for the central region of radio-quiet AGN in which coronal accretion is the source of energy for X-ray emission. We start from the Haardt & Maraschi model but supplement it with pressure balance condition, two…
Active galactic nuclei (AGN) are massive black holes (BHs) caught in the act of accreting gas at the centre of their host galaxies. Part of the accreting mass is converted to energy and released into the surrounding medium, in a process…
Warm absorbers are present in many Active Galactic Nuclei (AGN), seen as mildly ionised gas outflowing with velocities of a few hundred to a few thousand kilometres per second. These slow velocities imply a large launch radius, pointing to…
X-ray binary accretion disk winds can carry away a significant fraction of the matter transferred from the companion and hence strongly affect the accretion flow and the long-term evolution of the binary. However, accurate mass outflow rate…
X-ray observations of the tidal disruption event (TDE) candidate AT 2019avd show drastic variabilities in flux and spectral shape over hundreds of days, providing clues on the accretion disc-corona evolution. We utilize a disc-corona model,…
We study an accretion disc with a hot continuous corona. We assume that the corona itself accretes and therefore it is powered directly by the release of the gravitational energy and cooled by radiative interaction with the disc. We…
In order to provide an explanation for the unexpected radial brightness distribution of the steady accretion discs seen in nova-like variables, Nixon & Pringle (2019) proposed that the accretion energy is redistributed outwards by means of…
I present the elements of accretion-disc physics applied to active galactic nuclei. The accretion driving mechanisms are discussed, then models of geometrically-thin discs, both stationary and time-dependent, are addressed. Disc's…