Testing the Schwarzschild metric in a strong field region with the Event Horizon Telescope

Abstract

Testing gravity theory in the strong field region becomes a reality due to the observations of gravitational waves and black hole shadows. In this paper, we discuss how to constrain the possible deviations of the classical general relativity with the image of M87* observed by the Event Horizon Telescope. More precisely, we want to know where is the event horizon for a non-rotating black hole. General relativity predicts the horizon is located at the Schwarzschild radius $r_{\text{s}}$, while other gravity theories may give different predictions. We propose a parameterized Schwarzschild metric (PSM) in which the horizon is located at $r=n{r}_{\text{s}}$, where $n$ is a real free parameter, and prove general relativity with nonlinear electrodynamics allows $n\ne 1$. In the weak field region, the PSM is equivalent to the Schwarzschild metric regardless of the value of $n$. In the strong field region, the difference between the PSM and Schwarzschild metric would leave an imprint on the shadow image. We present detailed calculations and discussions on the black hole shadows with large background light source and accretion disk in the PSM framework. More importantly, we point out that $n\approx 2$ can be used to explain why the black hole mass measured by the shadow is a factor of about two larger than the previous gas dynamics measurements. If this explanation is confirmed to be right, then this phenomenon, together with the late-time cosmological acceleration, will be very important to test gravity theories.

14 pages, 9 figures, PRD accepted

References in corpus (38)

• Unified cosmic history in modified gravity: from F(R) theory to Lorentz non-invariant models
• First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole
• The Confrontation between General Relativity and Experiment
• First M87 Event Horizon Telescope Results. VI. The Shadow and Mass of the Central Black Hole
• First M87 Event Horizon Telescope Results. IV. Imaging the Central Supermassive Black Hole
• First M87 Event Horizon Telescope Results. V. Physical Origin of the Asymmetric Ring
• Beyond the Cosmological Standard Model
• First M87 Event Horizon Telescope Results. II. Array and Instrumentation
• Dark Energy after GW170817: dead ends and the road ahead
• First M87 Event Horizon Telescope Results. III. Data Processing and Calibration
• Strong constraints on cosmological gravity from GW170817 and GRB 170817A
• Implications of the Neutron Star Merger GW170817 for Cosmological Scalar-Tensor Theories
• Jet Launching Structure Resolved Near the Supermassive Black Hole in M87
• Shadow of a black hole surrounded by dark matter
• Solar System constraints to general f(R) gravity
• A new method for shadow calculations: application to parameterised axisymmetric black holes
• The Newtonian Limit of F(R) gravity
• The Black Hole Mass, Stellar M/L, and Dark Halo in M87
• Spontaneously scalarised Kerr black holes
• Non-Spinning Black Holes in Alternative Theories of Gravity
• Shadow of a Kaluza-Klein rotating dilaton black hole
• New parametrization for spherically symmetric black holes in metric theories of gravity
• Ultra Light Boson Dark Matter and Event Horizon Telescope Observations of M87*
• Fundamental photon orbits: black hole shadows and spacetime instabilities
• Black hole shadow in a general rotating spacetime obtained through Newman-Janis algorithm
• Vainshtein mechanism after GW170817
• Shadow casted by a Konoplya-Zhidenko rotating non-Kerr black hole
• Asymptotic safety casts its shadow
• Analytical representation for metrics of scalarized Einstein-Maxwell black holes and their shadows
• Regular Multi-Horizon Black Holes in Modified Gravity with Non-Linear Electrodynamics
• Simulations of imaging the event horizon of Sagittarius A* from space
• Testing General Relativity with Accretion-Flow Imaging of Sgr A*
• Regular multihorizon black holes in $f(G)$ gravity with nonlinear electrodynamics
• Black Hole Spin Signature in the Black Hole Shadow of M87 in the Flaring State
• Comments on "Solar System constraints to general f(R) gravity"
• Experimental Relativity with Accretion Disk Observations
• Newtonian approximation and possible time-varying $G$ in nonlocal gravities
• Constraints on Black Hole Jet Models Used As Diagnostic Tools of Event Horizon Telescope Observations of M87

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