Extreme gravitational lensing near rotating black holes

By Kristian Beckwith, C. Done. 2004

139 citations recorded by the source corpus.

We describe a new approach to calculating photon trajectories and gravitational lensing effects in the strong gravitational field of the Kerr black hole. These techniques are applied to explore both the imaging and spectral properties of photons emitted from an accretion disc, which perform multiple orbits of the central mass before escaping to infinity. Viewed at large inclinations, these higher-order photons contribute ∼20 per cent of the total luminosity of the system for a Schwarzschild hole, while for an extreme Kerr black hole this fraction rises to ∼60 per cent. In more realistic models, these photons will be reabsorbed by the disc at large distances from the hole, but this returning radiation could provide a physical mechanism to resolve the discrepancy between the predicted and observed optical/ultraviolet colours in active galactic nuclei. Conversely, at low inclinations, higher-order images reintercept the disc plane close to the black hole, so need not be absorbed by the disc if this is within the plunging region. These photons form a bright ring carrying approximately 10 per cent of the total disc luminosity for a Schwarzschild black hole. The spatial separation between the inner edge of the disc and the ring is similar to the size of the event horizon. This is resolvable for supermassive black holes with proposed X-ray interferometery missions such as the Microarcsecond X-ray Imaging Mission (MAXIM), and so has the potential to provide an observational test of strong field gravity.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/d0b5278449cb6f0da89cc228bfa126848a2e3252

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Citations in the corpus

TESTING THE NO-HAIR THEOREM WITH OBSERVATIONS IN THE ELECTROMAGNETIC SPECTRUM. II. BLACK HOLE IMAGES (2010, background): “…within general relativity that are suitable to these observations have been reported by a number of authors (Bardeen 1973; Speith et al. 1995; Fanton et al. 1997; Falcke et al. 2000; Takahashi 2004; Beckwith & Done 2004, 2005; Dexter & Agol 2009; Broderick & Loeb 2005, 2006; Yuan et al. 2009).”
TESTING THE NO-HAIR THEOREM WITH OBSERVATIONS IN THE ELECTROMAGNETIC SPECTRUM. IV. RELATIVISTICALLY BROADENED IRON LINES (2012, background): “In particular, we showed that a bright and narrow ring that surrounds the shadow of a black hole with a diameter of about 10M (see also, e.g., Beckwith & Done 2005) has a shape that depends uniquely on the mass, spin, quadrupole moment, and inclination of the black hole (see Psaltis & Johannsen…”
Twisting of light around rotating black holes (2011, background): “Patterns drawn by such beams experience an anamorphosi”
Black hole shadows, photon rings, and lensing rings (2019, background): “For emission from an accretion disk, the main dark area extends simply to the lensed position of the inner edge of the disk [8,12].”
The shape of the black hole photon ring: A precise test of strong-field general relativity (2020, unknown): “The orbiting photons all arrive near a closed, “ critical curve ” ontheimage plane, creatinga ringlike feature known as the photon ring [8,11 – 15].”
Lensing by Kerr black holes (2019, unknown): “Photons executing of order one orbit or more contribute a sequence of highly demagnified images near the critical curve [15,16,20,21].”
PHOTON RINGS AROUND KERR AND KERR-LIKE BLACK HOLES (2013, background): “Images of photon rings around Kerr black holes have already been calculated by several authors (e.g., Bardeen 1973; Luminet 1979; Takahashi 2004; Beckwith & Done 2005; JP10b; Chan et al. 2013).”
Imaging bright-spots in the accretion flow near the black hole horizon of Sgr A* (2005, background): “The significance of these in the context of the Fe Kα lines has been previously noted by Beckwith & Done (2005).”