scholarly journals Brightness Asymmetry of Black Hole Images as a Probe of Observer Inclination

2022 ◽  
Vol 924 (2) ◽  
pp. 46
Author(s):  
Lia Medeiros ◽  
Chi-Kwan Chan ◽  
Ramesh Narayan ◽  
Feryal Özel ◽  
Dimitrios Psaltis
Keyword(s):  
Black Hole ◽  
Necessary Condition ◽  
Flow Models ◽  
Supermassive Black Hole ◽  
The North ◽  
North Side ◽  
Test Particles ◽  
Angular Velocities ◽  
General Relativistic ◽  
Magnetohydrodynamic Simulations

Abstract The Event Horizon Telescope recently captured images of the supermassive black hole in the center of the M87 galaxy, which shows a ring-like emission structure with the south side only slightly brighter than the north side. This relatively weak asymmetry in the brightness profile along the ring has been interpreted as a consequence of the low inclination of the observer (around 17° for M87), which suppresses the Doppler beaming and boosting effects that might otherwise be expected due to the nearly relativistic velocities of the orbiting plasma. In this work, we use a large suite of general relativistic magnetohydrodynamic simulations to reassess the validity of this argument. By constructing explicit counterexamples, we show that low inclination is a sufficient but not necessary condition for images to have low brightness asymmetry. Accretion flow models with high accumulated magnetic flux close to the black hole horizon (the so-called magnetically arrested disks) and low black hole spins have angular velocities that are substantially smaller than the orbital velocities of test particles at the same location. As a result, such models can produce images with low brightness asymmetry even when viewed edge on.

scholarly journals How to tell an accreting boson star from a black hole

2020 ◽  
Vol 497 (1) ◽  
pp. 521-535 ◽  
Author(s):  
Hector Olivares ◽  
Ziri Younsi ◽  
Christian M Fromm ◽  
Mariafelicia De Laurentis ◽  
Oliver Porth ◽  
...  
Keyword(s):  
Black Hole ◽  
Radiative Transfer ◽  
Event Horizon ◽  
Polar Regions ◽  
Radio Observations ◽  
Accretion Flow ◽  
Supermassive Black Hole ◽  
General Relativistic ◽  
Sgr A ◽  
Magnetohydrodynamic Simulations

ABSTRACT The capability of the Event Horizon Telescope (EHT) to image the nearest supermassive black hole candidates at horizon-scale resolutions offers a novel means to study gravity in its strongest regimes and to test different models for these objects. Here, we study the observational appearance at 230 GHz of a surfaceless black hole mimicker, namely a non-rotating boson star, in a scenario consistent with the properties of the accretion flow on to Sgr A*. To this end, we perform general relativistic magnetohydrodynamic simulations followed by general relativistic radiative transfer calculations in the boson star space–time. Synthetic reconstructed images considering realistic astronomical observing conditions show that, despite qualitative similarities, the differences in the appearance of a black hole – either rotating or not – and a boson star of the type considered here are large enough to be detectable. These differences arise from dynamical effects directly related to the absence of an event horizon, in particular, the accumulation of matter in the form of a small torus or a spheroidal cloud in the interior of the boson star, and the absence of an evacuated high-magnetization funnel in the polar regions. The mechanism behind these effects is general enough to apply to other horizonless and surfaceless black hole mimickers, strengthening confidence in the ability of the EHT to identify such objects via radio observations.

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 The effects of resolution on black hole accretion simulations of jets

2020 ◽  
Vol 498 (2) ◽  
pp. 2428-2439
Author(s):  
Christopher J White ◽  
Fiona Chrystal
Keyword(s):  
Black Hole ◽  
Velocity Structure ◽  
Grid Resolution ◽  
Black Hole Accretion ◽  
General Relativistic ◽  
Axisymmetric Structure ◽  
Magnetohydrodynamic Simulations ◽  
Jet Power ◽  
Hole Accretion

ABSTRACT We perform three general-relativistic magnetohydrodynamic simulations of black hole accretion designed to test how sensitive results are to grid resolution in the jet region. The cases differ only in numerics, modelling the same physical scenario of a radiatively inefficient, geometrically thick, magnetically arrested flow on to a rapidly spinning black hole. Properties inferred with the coarsest grid generally agree with those found with higher resolutions, including total jet power and its decomposition into different forms, velocity structure, non-axisymmetric structure, and the appearance of resolved millimetre images. Some measures of variability and magnetization are sensitive to resolution. We conclude that most results obtained by limiting resolution near the jet for computational expediency should still be reliable, at least in so far as they would not be improved with a finer grid.

scholarly journals Disc Tearing and Bardeen-Petterson Alignment in GRMHD Simulations of Highly Tilted Thin Accretion Discs

2020 ◽  
Author(s):  
M Liska ◽  
C Hesp ◽  
A Tchekhovskoy ◽  
A Ingram ◽  
M van der Klis ◽  
...  
Keyword(s):  
Black Hole ◽  
Galactic Nuclei ◽  
Accretion Discs ◽  
Emission Model ◽  
Sharp Drop ◽  
Frame Dragging ◽  
General Relativistic ◽  
Magnetohydrodynamic Simulations ◽  
Future Work ◽  
X Ray Binaries

Abstract Luminous active galactic nuclei (AGN) and X-Ray binaries (XRBs) often contain geometrically thin, radiatively cooled accretion discs. According to theory, these are – in many cases – initially highly misaligned with the black hole equator. In this work, we present the first general relativistic magnetohydrodynamic simulations of very thin (h/r∼0.015-0.05) accretion discs around rapidly spinning (a∼0.9) black holes and tilted by 45-65 degrees. We show that the inner regions of the discs with h/r≲0.03 align with the black hole equator, though out to smaller radii than predicted by analytic work. The inner aligned and outer misaligned disc regions are separated by a sharp break in tilt angle accompanied by a sharp drop in density. We find that frame-dragging by the spinning black hole overpowers the disc viscosity, which is self-consistently produced by magnetized turbulence, tearing the disc apart and forming a rapidly precessing inner sub-disc surrounded by a slowly precessing outer sub-disc. We find that the system produces a pair of relativistic jets for all initial tilt values. At small distances the black hole launched jets precess rapidly together with the inner sub-disc, whereas at large distances they partially align with the outer sub-disc and precess more slowly. If the tearing radius can be modeled accurately in future work, emission model independent measurements of black hole spin based on precession-driven quasi-periodic oscillations may become possible.

scholarly journals General Relativistic Magnetohydrodynamic Simulations of Collapsars: Rotating Black Hole Cases

2004 ◽  
Vol 615 (1) ◽  
pp. 389-401 ◽  
Author(s):  
Yosuke Mizuno ◽  
Shoichi Yamada ◽  
Shinji Koide ◽  
Kazunari Shibata
Keyword(s):  
Black Hole ◽  
Rotating Black Hole ◽  
General Relativistic ◽  
Magnetohydrodynamic Simulations

scholarly journals Particle acceleration and the origin of the very high energy emission around black holes and relativistic jets

2020 ◽  
Vol 14 (S342) ◽  
pp. 13-18
Author(s):  
Elisabete M. de Gouveia Dal Pino ◽  
Grzegorz Kowal ◽  
Luis Kadowaki ◽  
Tania E. Medina-Torrejón ◽  
Yosuke Mizuno ◽  
...  
Keyword(s):  
Black Hole ◽  
Particle Acceleration ◽  
Magnetic Reconnection ◽  
High Energy ◽  
Black Hole Binaries ◽  
Mhd Instabilities ◽  
Test Particles ◽  
Very High Energy ◽  
General Relativistic ◽  
Very High

AbstractParticle acceleration induced by fast magnetic reconnection may help to solve current puzzles related to the interpretation of the very high energy (VHE) and neutrino emissions from AGNs and compact sources in general. Our general relativistic-MHD simulations of accretion disk-corona systems reveal the growth of turbulence driven by MHD instabilities that lead to the development of fast magnetic reconnection in the corona. In addition, our simulations of relativistic MHD jets reveal the formation of several sites of fast reconnection induced by current-driven kink turbulence. The injection of thousands of test particles in these regions causes acceleration up to energies of several PeVs, thus demonstrating the ability of this process to accelerate particles and produce VHE and neutrino emission, specially in blazars. Finally, we discuss how reconnection can also explain the observed VHE luminosity-black hole mass correlation, involving hundreds of non-blazar sources like Perseus A, and black hole binaries.

scholarly journals HOŘAVA–LIFSHITZ GRAVITY: TIGHTER CONSTRAINTS FOR THE KEHAGIAS–SFETSOS SOLUTION FROM NEW SOLAR SYSTEM DATA

2011 ◽  
Vol 20 (06) ◽  
pp. 1079-1093 ◽  
Author(s):  
L. IORIO ◽  
M. L. RUGGIERO
Keyword(s):  
Black Hole ◽  
Solar System ◽  
Lower Bounds ◽  
Modified Gravity ◽  
The Sun ◽  
Supermassive Black Hole ◽  
The Earth ◽  
Test Particles ◽  
The Galaxy ◽  
System Data

We analytically work out the perturbation Δρ induced by the Kehagias–Sfetsos (KS) spacetime solution of the Hořava–Lifshitz (HL) modified gravity at long distances on the two-body range ρ for a pair of test particles A and B orbiting the same mass M. We apply our results to the most recently obtained range residuals δρ for some planets of the solar system (Mercury, Mars, Saturn) ranged from the Earth to effectively constrain the dimensionless KS parameter ψ0 for the Sun. We obtain [Formula: see text] (Mercury), [Formula: see text] (Mars), and [Formula: see text] (Saturn). Such lower bounds are tighter than others existing in the literature by several orders of magnitude. We also preliminarily obtain [Formula: see text] for the system constituted by the S2 star orbiting the supermassive black hole (SBH) in the center of the galaxy.

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