scholarly journals General relativistic effects on Hill stability of multibody systems: Stability of three-body systems containing a massive black hole

2020 ◽  
Vol 102 (12) ◽  
Author(s):  
Haruka Suzuki ◽  
Yusuke Nakamura ◽  
Shoichi Yamada
Keyword(s):  
Black Hole ◽  
Multibody Systems ◽  
Relativistic Effects ◽  
Massive Black Hole ◽  
Hill Stability ◽  
General Relativistic ◽  
Three Body

scholarly journals Relative depolarization of the black hole photon ring in GRMHD models of Sgr A* and M87*

2021 ◽  
Vol 503 (3) ◽  
pp. 4563-4575
Author(s):  
A Jiménez-Rosales ◽  
J Dexter ◽  
S M Ressler ◽  
A Tchekhovskoy ◽  
M Bauböck ◽  
...  
Keyword(s):  
Black Hole ◽  
Relativistic Effects ◽  
Image Features ◽  
Black Hole Mass ◽  
Magnetic Turbulence ◽  
Intensity Images ◽  
General Relativistic ◽  
Sharp Image ◽  
Sgr A ◽  
Magnetohydrodynamic Simulations

ABSTRACT Using general relativistic magnetohydrodynamic simulations of accreting black holes, we show that a suitable subtraction of the linear polarization per pixel from total intensity images can enhance the photon ring feature. We find that the photon ring is typically a factor of ≃2 less polarized than the rest of the image. This is due to a combination of plasma and general relativistic effects, as well as magnetic turbulence. When there are no other persistently depolarized image features, adding the subtracted residuals over time results in a sharp image of the photon ring. We show that the method works well for sample, viable GRMHD models of Sgr A* and M87*, where measurements of the photon ring properties would provide new measurements of black hole mass and spin, and potentially allow for tests of the ‘no-hair’ theorem of general relativity.

scholarly journals High-Frequency QPOs and Overstable Oscillations of Black-Hole Accretion Disks

2012 ◽  
Vol 8 (S290) ◽  
pp. 57-61 ◽  
Author(s):  
Dong Lai ◽  
Wen Fu ◽  
David Tsang ◽  
Jiri Horak ◽  
Cong Yu
Keyword(s):  
Black Hole ◽  
Accretion Disks ◽  
High Frequency ◽  
Oscillation Mode ◽  
Relativistic Effects ◽  
X Ray ◽  
Black Hole Accretion ◽  
General Relativistic ◽  
X Ray Binaries ◽  
Hole Accretion

AbstractThe physical origin of high-frequency QPOs (HFQPOs) in black-hole X-ray binaries remains an enigma despite many years of detailed observational studies. Although there exists a number of models for HFQPOs, many of these are simply “notions” or “concepts” without actual calculation derived from fluid or disk physics. Future progress requires a combination of numerical simulations and semi-analytic studies to extract physical insights. We review recent works on global oscillation modes in black-hole accretion disks, and explain how, with the help of general relativistic effects, the energy stored in the disk differential rotation can be pumped into global spiral density modes in the disk, making these modes grow to large amplitudes under certain conditions (“corotational instability”). These modes are robust in the presence of disk magnetic fields and turbulence. The computed oscillation mode frequencies are largely consistent with the observed values for HFQPOs in BH X-ray binaries. The approximate 2:3 frequency ratio is also expected from this model. The connection of HFQPOs with other disk properties (such as production of episodic jets) is also discussed.

scholarly journals Stellar hardening of massive black hole binaries: the impact of the host rotation

2021 ◽  
Vol 508 (1) ◽  
pp. 1533-1542
Author(s):  
Ludovica Varisco ◽  
Elisa Bortolas ◽  
Massimo Dotti ◽  
Alberto Sesana
Keyword(s):  
Black Hole ◽  
Angular Momentum ◽  
Equal Mass ◽  
Stellar Systems ◽  
Massive Black Hole ◽  
Loss Cone ◽  
Black Hole Binaries ◽  
Influence Radius ◽  
Three Body ◽  
The Impact

ABSTRACT Massive black hole binaries (MBHBs) with masses of ∼104 to $\sim 10^{10} \, \mathrm{M}_{\odot {}}$ are one of the main targets for currently operating and forthcoming space-borne gravitational wave observatories. In this paper, we explore the effect of the stellar host rotation on the bound binary hardening efficiency, driven by three-body stellar interactions. As seen in previous studies, we find that the centre of mass (CoM) of a prograde MBHB embedded in a rotating environment starts moving on a nearly circular orbit about the centre of the system shortly after the MBHB binding. In our runs, the oscillation radius is ≈ 0.25 (≈ 0.1) times the binary influence radius for equal mass MBHBs (MBHBs with mass ratio 1:4). Conversely, retrograde binaries remain anchored about the centre of the host. The binary shrinking rate is twice as fast when the binary CoM exhibits a net orbital motion, owing to a more efficient loss cone repopulation even in our spherical stellar systems. We develop a model that captures the CoM oscillations of prograde binaries; we argue that the CoM angular momentum gain per time unit scales with the internal binary angular momentum, so that most of the displacement is induced by stellar interactions occurring around the time of MBHB binding, while the subsequent angular momentum enhancement gets eventually quashed by the effect of dynamical friction. The effect of the background rotation on the MBHB evolution may be relevant for LISA sources, that are expected to form in significantly rotating stellar systems.

scholarly journals RELXILL_NK: A Black Hole Relativistic Reflection Model for Testing General Relativity

Proceedings ◽  
2019 ◽  
Vol 17 (1) ◽  
pp. 7 ◽  
Author(s):  
Askar B. Abdikamalov ◽  
Dimitry Ayzenberg ◽  
Cosimo Bambi  ◽  
Sourabh Nampalliwar
Keyword(s):  
General Relativity ◽  
Black Hole ◽  
Relativistic Effects ◽  
Asymptotically Flat ◽  
X Ray ◽  
Black Hole Accretion ◽  
Reflection Model ◽  
Black Hole Spacetime ◽  
General Relativistic ◽  
Hole Accretion

In this paper, we briefly present RELXILL_NK, the first and currently only readily available model of the relativistic reflection spectrum of black hole accretion disks that includes non-Kerr solutions for the black hole spacetime, thus allowing for tests of the Kerr hypothesis and general relativity (GR). RELXILL_NK makes use of a general relativistic ray-tracing code to calculate the relativistic effects of any well-behaved, stationary, axisymmetric, and asymptotically flat black hole spacetime, while the disk physics is handled through the non-relativistic X-ray reflection code XILLVER. A number of different flavors are available within RELXILL_NK; we summarize and compare these flavors using the Johannsen metric for the black hole spacetime.

scholarly journals Gravitating Disks Around Black Holes

2009 ◽  
Vol 5 (S267) ◽  
pp. 332-332
Author(s):  
Vladimír Karas ◽  
Ladislav Šubr
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Gravitational Field ◽  
Relativistic Effects ◽  
Einstein Equations ◽  
Axially Symmetric ◽  
Disk System ◽  
Massive Black Hole ◽  
Black Hole Binary

AbstractFluid disks and tori around black holes are discussed within different approaches and with the emphasis on the role of disk gravity. We first review the prospects for investigating the gravitational field of a black hole–disk system by analytical solutions of stationary, axially symmetric Einstein equations. More detailed considerations are focused on the middle and outer parts of extended disk-like configurations where relativistic effects are small and the Newtonian description is adequate. As an example, we investigate the case of a torus near a massive black hole that is a member of the black-hole binary system.

scholarly journals Power spectra from spotted accretion discs

2006 ◽  
Vol 2 (S238) ◽  
pp. 425-426
Author(s):  
Tomáš Pecháček ◽  
Michal Dovčiak ◽  
Vladimír Karas
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Binary Systems ◽  
Power Spectra ◽  
Galactic Nuclei ◽  
Relativistic Effects ◽  
Power Spectral ◽  
Power Spectral Densities ◽  
Galactic Black Hole ◽  
General Relativistic

AbstractSome aspects of power-spectral densities (PSD) of active galactic nuclei are similar to those of galactic black hole X-ray binary systems (McHardy et al. 2005). The signal originates near a black hole and its modulation by general-relativistic effects should be taken into account (Życki & Nedźwiecki 2005). We modified the previous calculations of these effects, assuming a model of spots which occur on the disc surface and decay with a certain lifetime.

scholarly journals General-relativistic instability in hylotropic supermassive stars

2020 ◽  
Vol 644 ◽  
pp. A154
Author(s):  
L. Haemmerlé
Keyword(s):  
Black Hole ◽  
Stellar Evolution ◽  
Total Mass ◽  
Hole Formation ◽  
Massive Black Hole ◽  
Core Mass ◽  
Accretion Rates ◽  
General Relativistic ◽  
High Level ◽  
Stellar Masses

Context. The formation of supermassive black holes by direct collapse would imply the existence of supermassive stars (SMSs) and their collapse through the general-relativistic (GR) instability into massive black hole seeds. However, the final mass of SMSs is weakly constrained by existing models, in spite of the importance of this value for the consistency of the direct collapse scenario. Aims. We estimate the final masses of spherical SMSs within the whole parameter space that is relevant to these objects. Methods. We built analytical stellar structures (hylotropes) that mimic existing numerical SMS models, accounting for full stellar evolution with rapid accretion. From these hydrostatic structures, we determine ab initio the conditions for GR instability and compare the results with the predictions for full stellar evolution. Results. We show that hylotropic models predict the onset of GR instability with a high level of precision. The mass of the convective core appears as a decisive quantity. The lower it is, the larger the total mass required for GR instability. The typical conditions for GR instability feature a total mass of ≳105 M⊙ with a core mass of ≳104 M⊙. If the core mass remains below 104 M⊙, total masses in excess of 106 − 107 M⊙ can be reached. Conclusions. Our results confirm that spherical SMSs forming in primordial, atomically cooled haloes collapse at masses below 500 000 M⊙. On the other hand, accretion rates in excess of 1000 M⊙ yr−1, leading to final stellar masses of ≳106 M⊙, are required for massive black hole formation in metal-rich gas. Thus, the different channels of direct collapse imply distinct final masses for the progenitor of the black hole seed.

scholarly journals A study on tidal disruption event dynamics around an Sgr A*-like massive black hole

2020 ◽  
Vol 642 ◽  
pp. A111
Author(s):  
A. Clerici ◽  
A. Gomboc
Keyword(s):  
Black Hole ◽  
Relativistic Effects ◽  
Dynamical Behaviour ◽  
Return Rate ◽  
Newtonian Potential ◽  
Tidal Disruption ◽  
Massive Black Hole ◽  
Orbital Parameters ◽  
Sgr A ◽  
Disruption Event

Context. The number of observed tidal disruption events is increasing rapidly with the advent of new surveys. Thus, it is becoming increasingly important to improve tidal disruption event models using different stellar and orbital parameters. Aims. We study the dynamical behaviour of tidal disruption events produced by an Sgr A*-like massive black hole by changing different initial orbital parameters, taking into account the observed orbits of S stars. Investigating different types of orbits and penetration factors is important since their variations lead to different timescales of the tidal disruption event debris dynamics, making mechanisms such as self-crossing and pancaking act strongly or weakly and thus affecting the circularisation and accretion disc formation. Methods. We performed smoothed particle hydrodynamics simulations. Each simulation consisted of modelling the star with 105 particles, and the density profile is described by a polytrope with γ = 5/3. The massive black hole was modelled with a generalised post-Newtonian potential, which takes into account the relativistic effects of the Schwarzschild space-time. Results. Our analyses find that mass return rate distributions of solar-like stars and S-like stars with the same eccentricities have similar durations, but S-like stars have higher mass return rate distributions, as expected due to their larger masses. Regarding debris circularisation, we identify four types of evolution related to the mechanisms and processes involved during circularisation: in type 1, the debris does not circularise efficiently, hence a disc is not formed or is formed after a relatively long time; in type 2, the debris slowly circularises and eventually forms a disc with no debris falling back; in type 3, the debris circularises relatively quickly and forms a disc while there is still debris falling back; in type 4, the debris quickly and efficiently circularises, mainly through self-crossings and shocks, and forms a disc with no debris falling back. Finally, we find that the standard relation of circularisation radius rcirc = 2rt holds only for β = 1 and eccentricities close to parabolic.

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