Related papers: Radiatively Inefficient Accretion Flow Models of S…
The super-massive 4 million solar mass black hole (SMBH) SgrA* shows variable emission from the millimeter to the X-ray domain. A detailed analysis of the infrared light curves allows us to address the accretion phenomenon in a statistical…
Two independent sets of Chandra and HST images of the nuclear region of M31 allow registration of X-ray and optical images to 0.1''. This registration shows that none of the bright (10^{37} erg/s) X-ray sources near the nucleus is…
We study the properties of rotating accretion flows onto supermassive black holes (SMBHs) using axisymmetric two-dimensional hydrodynamical simulations with radiative cooling and BH feedback. The simulations resolve the accretion dynamics…
The candidate supermassive black hole in the Galactic Centre, Sagittarius A* (Sgr A*), is known to be fed by a radiatively inefficient accretion flow (RIAF), inferred by its low accretion rate. Consequently, radiative cooling has in general…
Accretion in black hole X-ray binaries is commonly believed to be supplied by the Roche lobe overflow or the stellar wind. The former is thought to form a geometrically thin disc while the diffuse wind could form a geometrically thick hot…
We present a new code for performing general-relativistic radiation-hydrodynamics simulations of accretion flows onto black holes. The radiation field is treated in the optically-thick approximation, with the opacity contributed by Thomson…
We develop an analytic, steady-state model for the gas environment in quiescent galactic nuclei. We assume that the mass is constantly supplied by a spherically symmetric distribution of wind emitting stars, and that gravity is solely due…
Sgr A*, the 4 x 10^6 solar-mass supermassive black hole at the Galactic Center, exhibits frequent flaring with X-ray luminosities of L_X ~ 10^35--10^36 erg s^-1, while its ultraviolet (UV) emission remains unconstrained due to extreme…
Hydrodynamic simulations of the stellar winds from Wolf-Rayet stars within the Galactic Center can provide predictions for the X-ray spectrum of supermassive black hole Sgr A*. Herein, we present results from updated smooth particle…
Sgr A* is an ideal target to study low-luminosity accreting systems. It has been recently proposed that properties of the accretion flow around Sgr A* can be probed through its interactions with the stellar wind of nearby massive stars…
In this paper, we present the classical Bondi accretion theory for the case of non-isothermal accretion processes onto a supermassive black hole (SMBH), including the effects of X-ray heating and the radiation force due to electron…
The X-ray and near-IR emission from Sgr A* is dominated by flaring, while a quiescent component dominates the emission at radio and sub-mm wavelengths. The spectral energy distribution of the quiescent emission from Sgr A* peaks at sub-mm…
(Abridged) Among the various issues that remain open in the field of accretion onto black hole X-ray binaries (BHBs) is the way the gas accretes at very low Eddington ratios, in the so-called quiescent regime. While there is general…
The centre of our Galaxy harbours a 4 million solar mass black hole that is unusually quiet: its present X-ray luminosity is more than 10 orders of magnitude less than its Eddington luminosity. The observation of iron fluorescence and hard…
The supermassive black hole in the center of the Milky Way, Sgr A*, displays a nearly flat radio spectrum that is typical for jets in active galactic nuclei. Indeed, time-dependent magnetized models of radiatively inefficient accretion…
We present Athena++ grid-based, hydrodynamic simulations of accretion onto Sagittarius A* via the stellar winds of the $\sim 30$ Wolf-Rayet stars within the central parsec of the galactic center. These simulations span $\sim$ 4 orders of…
The low-luminosity black hole Sgr A* provides a testbed for models of Radiatively Inefficient Accretion Flows (RIAFs). Recent sub-millimeter linear polarization measurements of Sgr A* have provided evidence that the electrons in the…
The quiescent state is the dominant accretion mode for black holes on all mass scales. Our knowledge of the X-ray spectrum is limited due to the characteristic low luminosity in this state. Herein, we present an analysis of the sample of…
The Event Horizon Telescope (EHT) Collaboration produced the first image of the apparent shadow of the central black hole of Sagittarius\,A$^*$ (\sgra). \sgra source structure varies significantly on timescales shorter than the duration of…
The Galaxy's supermassive black hole, Sgr A*, produces an outburst of infrared radiation about once every 6 hours, sometimes accompanied by an even more energetic flurry of X-rays. The NIR photons are produced by nonthermal synchrotron…