The light ring and the appearance of matter accreted by black holes

Abstract

The geometry of black hole spacetimes can be probed with exquisite precision in the gravitational-wave window, and possibly also in the optical regime. We study the accretion of bright spots -- objects which emit strongly in the optical or in gravitational waves -- by non-spinning black holes. The emission as the object falls down the hole is dominated by photons or gravitons orbiting the light ring, causing the total luminosity to decrease exponentially as ${\mathcal{L}}_o\sim e^{-t/(3\sqrt{3}M)}$. Late-time radiation is blueshifted, due to its having been emitted during the infall, trapped at the light ring and subsequently re-emitted. These universal properties are a clear signature of the existence of light rings in the spacetime, and not particularly sensitive to near horizon details.

11 pages, 10 figures, revtex4. v2: Several improvements, relation between geometric optics and quasinormal modes clarified. To appear in Physical Review D

References in corpus (12)

• First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole
• Echoes of ECOs: gravitational-wave signatures of exotic compact objects and of quantum corrections at the horizon scale
• Detection of the Schwarzschild precession in the orbit of the star S2 near the Galactic centre massive black hole
• Light rings as observational evidence for event horizons: long-lived modes, ergoregions and nonlinear instabilities of ultracompact objects
• The Shape of the Black Hole Photon Ring: A Precise Test of Strong-Field General Relativity
• Testing the black hole "no-hair" hypothesis
• Quasinormal-mode spectrum of Kerr black holes and its geometric interpretation
• Towards adiabatic waveforms for inspiral into Kerr black holes: I. A new model of the source for the time domain perturbation equation
• Modeling the orbital motion of Sgr A*'s near-infrared flares
• A new gravitational wave generation algorithm for particle perturbations of the Kerr spacetime
• The Flux Distribution of Sgr A*
• Relating Black Hole Shadow to Quasinormal Modes for Rotating Black Holes

Cited by in corpus (22)

• Shadows of boson and Proca stars with thin accretion disks
• Shadows and rings of the Kehagias-Sfetsos black hole surrounded by thin disk accretion
• Analytical study of higher-order ring images of accretion disk around black hole
• Observational properties of relativistic fluid spheres with thin accretion disks
• Observational signatures of hot spots orbiting horizonless objects
• Shape of higher-order images of equatorial emission rings around a Schwarzschild black hole: Analytical description with polar curves
• Holography of the Photon Ring
• Light Ring behind Wormhole Throat: Geodesics, Images and Shadows
• Photon Ring Astrometry for Superradiant Clouds
• Geodesics and gravitational waves in chaotic extreme-mass-ratio inspirals: the curious case of Zipoy-Voorhees black-hole mimickers
• Shadows and optical appearance of quantum-corrected black holes illuminated by static thin accretions
• Quasinormal Modes and Universality of the Penrose Limit of Black Hole Photon Rings
• Observational Appearance of a Freely-falling Star in an Asymmetric Thin-shell Wormhole
• Extreme lensing induces spectro-temporal correlations in black-hole signals
• Divergences in gravitational-wave emission and absorption from extreme mass ratio binaries
• Measuring Black Hole Light Echoes with Very Long Baseline Interferometry
• Forward Ray Tracing and Hot Spots in Kerr Spacetime
• Photon emissions from near-horizon extremal and near-extremal Kerr equatorial emitters
• Photon emission from inside the innermost stable circular orbit
• Observability of Zero-angular-momentum Sources Near Kerr Black Holes
• Dynamical Lensing Tomography of Black Hole Ringdown
• Resonances, black hole mimickers and the greenhouse effect: consequences for gravitational-wave physics