The Shadow of a Spherically Accreting Black Hole

By Ramesh Narayan, Michael D. Johnson, Charles F. Gammie. Astrophysical Journal, 2019

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We explore a simple spherical model of optically thin accretion on a Schwarzschild black hole, and study the properties of the image as seen by a distant observer. We show that a dark circular region in the center—a shadow—is always present. The outer edge of the shadow is located at the photon ring radius , where is the gravitational radius of the accreting mass M. The location of the shadow edge is independent of the inner radius at which the accreting gas stops radiating. The size of the observed shadow is thus a signature of the spacetime geometry and it is hardly influenced by accretion details. We briefly discuss the relevance of these results for the Event Horizon Telescope image of the supermassive black hole in M87.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/1898ce275f0626e1337a8d2cf2b42432cb9d3257

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Citations in the corpus

Black holes with scalar hair in light of the Event Horizon Telescope (2020, background): “While this concern most certainly holds for the bright ring surrounding the dark region (whose size, morphology, and luminosity all depend very sensitively on the details of the accretion flow), it is known that for advection dominated accretion flow (ADAF) the dark region in VLBI-detected images is”
Influence of quintessence dark energy on the shadow of black hole (2020, background): “So far, the study of shadows of black holes has become a subject of great interest [12–39].”
First Sagittarius A* Event Horizon Telescope Results. IV. Variability, Morphology, and Black Hole Mass (2022, background): “…(e.g., Bardeen 1973; Luminet 1979; de Vries 2000; Falcke et al. 2000; Broderick & Loeb 2006; Broderick & Narayan 2006; Broderick et al. 2011, 2016; Narayan et al. 2019), and a variety of more general accretion flow simulations have demonstrated that the diameter of this ring is typically ∼5…”
Magnetically charged black holes from non-linear electrodynamics and the Event Horizon Telescope (2019, background): “Due to the combination of a photon sphere (where photons travel along unstable circular orbits) and gravitational lensing of photons, an accreting BH surrounded by a geometrically thick, optically thin emission region will lead to the appearance of a so-called shadow, in combination with a bright em”