Related papers: New Black Hole Spin Values for Sagittarius A* Obta…
Studies of black hole spin and other parameters as a function of redshift provide information about the physical state and merger and accretion histories of the systems. One way that black hole spin may be estimated is through observations…
The rotational properties of astrophysical black holes are fundamental quantities that characterization the black holes. A new method to empirically determine the spin mass-energy characteristics of astrophysical black holes is presented…
We determine the spin of a supermassive black hole in the context of discseismology by comparing newly detected quasi-periodic oscillations (QPOs) of radio emission in the Galactic centre, Sagittarius A* (Sgr A*), as well as infrared and…
Supermassive black holes may be described by their mass and spin. When supermassive black holes are active, the activity provides a probe of the state of the black hole system. The spin of a hole can be estimated when the black hole mass…
We obtain estimates of Sgr A* accretion flow and black hole parameters by fitting polarized sub-mm observations with spectra computed using three-dimensional (3D) general relativistic (GR) magnetohydrodynamical (MHD) (GRMHD) simulations.…
The polarized mm/sub-mm radiation from Sgr A* is apparently produced by a Keplerian structure whose peak emission occurs within several Schwarzschild radii (r_S=2GM/c^2) of the black hole. The Chandra X-ray counterpart, if confirmed, is…
The bright soft X-ray transient Nova Muscae 1991 was intensively observed during its entire 8-month outburst using the Large Area Counter (LAC) onboard the Ginga satellite. Recently, we obtained accurate estimates of the mass of the black…
The black hole spacetime is described by general relativity and characterized by two quantities: the black hole mass and spin. Black hole spin measurement requires information from the vicinity of the event horizon, which is spatially…
The mass of a black hole is the sum of the irreducible mass and the mass associated with the rotational or spin energy of the black hole. The contribution of spin energy (divided by $c^2$) to the total black hole mass is studied here for…
We study the properties of the dissipative accretion flow around rotating black holes in presence of mass loss. We obtain the complete set of global inflow-outflow solutions in the steady state by solving the underlying conservation…
During its yearlong outburst in 1975--76, the transient source A0620--00 reached an intensity of 50 Crab, an all-time record for any X-ray binary. The source has been quiescent since. We recently determined accurate values for the black…
Relationships between beam power and accretion disk luminosity are studied for a sample of 55 HERG, 13 LERG, and 29 RLQ with powerful outflows. The ratio of beam power to disk luminosity tends to be high for LERG, low for RLQ, and spans the…
Black hole systems, comprised of a black hole, accretion disk, and collimated outflow are studied here. Three AGN samples including 753 AGN, and 102 measurements of 4 GBH are studied. Applying the theoretical considerations described by…
I report the discovery of a new effect of General Relativity which is important to understand very rapidly rotating (Kerr) black holes. The orbital velocity of a test particle is no longer a monotonic function of the orbit radius when the…
MAXI J1820+070 is a newly-discovered black hole X-ray binary, whose dynamical parameters, namely the black hole mass, the inclination angle and the source distance, have been estimated recently. \emph{Insight}-HXMT have observed its entire…
A new approach to constraining or determining the spin of a massive black hole is proposed. A key parameter in the analysis is the dimensionless ratio, r, of the energy released to the mass of the hole. It is shown that the black hole spin,…
We report measurements with the Very Long Baseline Array of the proper motion of Sgr A* relative to two extragalactic radio sources spanning 18 years. The apparent motion of Sgr A* is -6.411 +/- 0.008 mas/yr along the Galactic plane and…
As a key science project of the Square Kilometre Array (SKA), the discovery and timing observations of radio pulsars in the Galactic Center would provide high-precision measurements of the spacetime around the supermassive black hole,…
Millimeter very-long baseline interferometry (mm-VLBI) provides the novel capacity to probe the emission region of a handful of supermassive black holes on sub-horizon scales. For Sagittarius A* (Sgr A*), the supermassive black hole at the…
I review the current status of X-ray reflection (a.k.a. broad iron line) based black hole spin measurements. This is a powerful technique that allows us to measure robust black hole spins across the mass range, from the stellar-mass black…