Black hole shadow in the view of freely falling observers

Abstract

First sketch of black hole from M87 galaxy was obtained by Event Horizon Telescope, recently. As appearance of black hole shadow reflects space-time geometry of black holes, observations of black hole shadow may be a promising way to test general relativity in strong field regime. In this paper, we focus on angular radius of spherical black hole shadow with respect to freely falling observers. In the framework of general relativity, aberration formulation and angular radius-gravitational redshift relation are presented. For the sake of intuitive, we consider parametrized Schwarzschild black hole and Schwarzschild-de Sitter black hole as representative examples. We find that the freely in-falling observers would observe finite size of shadow, when they go through inner horizon. For observers freely falling from the outer horizon of Schwarzschild-de Sitter black hole, we find that the angular radius of the shadows could increase even when the observers move farther from the black hole.

v1: 21 pages, 6 figures; v2: 31 pages, 11 figures, a revised version for publishing in JCAP

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• Shadow of a Spinning Black Hole in an Expanding Universe
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• Analytical study of higher-order ring images of accretion disk around black hole
• Shape of higher-order images of equatorial emission rings around a Schwarzschild black hole: Analytical description with polar curves
• Deflection of light rays by spherically symmetric black hole in dispersive medium
• Shadow cast by a rotating and nonlinear magnetic-charged black hole in perfect fluid dark matter
• Shadows of rotating Hayward-de Sitter black holes with astrometric observables
• The observer-dependent shadow of the Kerr black hole
• Dynamics of null particles and shadow for general rotating black hole
• Light from Schwarzschild Black Holes in de Sitter expanding universe
• Do black hole shadows merge?
• Observational signatures from higher-order images of moving hotspots in accretion disks
• Light from Reissner-Nordstrom-de Sitter black holes
• Aberration effect on lower-order images of thin accretion disk in the astrometric approach
• Shadows of quintessence black holes: spherical accretion, photon trajectories, and geodesic observers