Regular Article - Theoretical Physics
Qualifying ringdown and shadow of black holes under general parametrized metrics with photon orbits
Shanghai Astronomical Observatory, 200030, Shanghai, China
2 School of Astronomy and Space Science, University of Chinese Academy of Sciences, 100049, Beijing, China
3 Ulugh Beg Astronomical Institute, Astronomicheskaya 33, 100052, Tashkent, Uzbekistan
4 School of Fundamental Physics and Mathematical Sciences, Hangzhou Institute for Advanced Study, UCAS, 310024, Hangzhou, China
Accepted: 12 July 2021
Published online: 23 July 2021
The motion of photons around black holes determines the shape of shadow and match the ringdown properties of a perturbed black hole. Observations of shadows and ringdown waveforms will reveal the nature of black holes. In this paper, we study the motion of photons in a general parametrized metric beyond the Kerr hypothesis. We investigated the radius and frequency of the photon circular orbits on the equatorial plane and obtained fitted formula with varied parameters. The Lyapunov exponent which connects to the decay rate of the ringdown amplitude is also calculated. We also analyzed the shape of shadow with full parameters of the generally axisymmetric metric. Our results imply the potential constraint on black hole parameters by combining the Event Horizon Telescope and gravitational wave observations in the future.
© The Author(s) 2021
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