Black Hole Binaries in AGN Accretion Discs II: Gas Effects on Black Hole Satellite Scatterings
(2023)
Gas Assisted Binary Black Hole Formation in AGN Discs
(2023)
Search for Correlations of High-energy Neutrinos Detected in IceCube with Radio-bright AGN and Gamma-Ray Emission from Blazars
The Astrophysical Journal American Astronomical Society 954:1 (2023) 75
Resonant dynamical friction around a supermassive black hole: analytical description
Monthly Notices of the Royal Astronomical Society Oxford University Press 525:3 (2023) 4202-4218
Abstract:
We derive an analytical model for the so-called phenomenon of resonant dynamical friction, where a disc of stars around a supermassive black hole interacts with a massive perturber, so as to align its inclination with the disc’s orientation. We show that it stems from a singular behaviour of the orbit-averaged equations of motion, which leads to a rapid alignment of the argument of the ascending node of each of the disc stars, with that of the perturber, p, with a phase difference of 90◦. This phenomenon occurs for all stars whose maximum possible ˙ (maximized over all values of for all the disc stars) is greater than ˙ p; this corresponds approximately to all stars whose semi-major axes are less than twice that of the perturber. The rate at which the perturber’s inclination decreases with time is proportional to its mass and is shown to be much faster than Chandrasekhar’s dynamical friction. We find that the total alignment time is inversely proportional to the root of the perturber’s mass. This persists until the perturber enters the disc. The predictions of this model agree with a suite of numerical N-body simulations, which we perform to explore this phenomenon, for a wide range of initial conditions, masses, etc., and are an instance of a general phenomenon. Similar effects could occur in the context of planetary systems, too.
Quasi-periodic oscillations for spherically symmetric regular black holes
Physical Review D 108 4 044063
Abstract:
We consider the recent data sets of quasi-periodic oscillations from eight different low mass X-ray
binaries. We here interpret their physical features in the context of given regular black hole solutions
and verify their applicability to neutron star configurations. We evaluate the numerical constraints
over the free parameters of Bardeen, Hayward and Dymnikova regular solutions by performing a
set of Markov chain Monte Carlo analyses, based on the Metropolis algorithm. For each source, we
evaluate the best-fit parameters, among which mass and magnetic charge, and compare and contrast
them with the current literature. We also infer the corresponding innermost stable circular orbit
radii and the radial extents of the accretion disks. Focusing on how to identify discrepancies among
theoretical models and observations, our results show that, in most of the cases, regular black holes,
in particular the Bardeen and Hayward spacetimes are slightly more suitable to describe neutron
stars than Schwarzschild geometry, whereas the Dymnikova metric is ruled out.
binaries. We here interpret their physical features in the context of given regular black hole solutions
and verify their applicability to neutron star configurations. We evaluate the numerical constraints
over the free parameters of Bardeen, Hayward and Dymnikova regular solutions by performing a
set of Markov chain Monte Carlo analyses, based on the Metropolis algorithm. For each source, we
evaluate the best-fit parameters, among which mass and magnetic charge, and compare and contrast
them with the current literature. We also infer the corresponding innermost stable circular orbit
radii and the radial extents of the accretion disks. Focusing on how to identify discrepancies among
theoretical models and observations, our results show that, in most of the cases, regular black holes,
in particular the Bardeen and Hayward spacetimes are slightly more suitable to describe neutron
stars than Schwarzschild geometry, whereas the Dymnikova metric is ruled out.