2014/01/31 by G. V. Kraniotis · 2 citations
Physics and Astronomy · #Astrophysical Phenomena and Observations #Black hole (networking) #Charged black hole #Extremal black hole #Geodesics in general relativity #Gravitational field #Gravitational lens #Photon sphere #Pulsars and Gravitational Waves Research #Relativity and Gravitational Theory #Rotating black hole #White hole #astro-ph.GA #de Sitter–Schwarzschild metric #gr-qc
paper · pdf · doi:10.1007/s10714-014-1818-8
published as Gen. Relativ. Gravit. (2014) Vol.46, Number 11,1818 · updated version conforms to published version in General Relativity and Gravitation. The final Publication is available at Springer via http://dx.doi.org/10.1007/s10714-014-1818-8
openalex publication_date 2014/10/27 · arxiv created 2015/02/26 · arxiv updated 2015/02/27 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
The null geodesics that describe photon orbits in the spacetime of a rotating electrically charged black hole (Kerr-Newman) are solved exactly including the contribution from the cosmological constant. We derive elegant closed form solutions for relativistic observables such as the deflection angle and frame dragging effect that a light ray experiences in the gravitational fields (i) of a Kerr-Newman black hole and (ii) of a Kerr-Newman-de Sitter black hole. We then solve the more involved problem of treating a Kerr-Newman black hole as a gravitational lens, i.e. a KN black hole along with a static source of light and a static observer both located far away but otherwise at arbitrary positions in space. For this model, we derive the analytic solutions of the lens equations in terms of Appell and Lauricella hypergeometric functions and the Weierstraßmodular form. The exact solutions derived for null, spherical polar and non-polar orbits, are applied for the calculation of frame dragging for the orbit of a photon around the galactic centre, assuming that the latter is a Kerr-Newman black hole. We also apply the exact solution for the deflection angle of an equatorial light ray in the gravitational field of a Kerr-Newman black hole for the calculation of bending of light from the gravitational field of the galactic centre for various values of the Kerr parameter, electric charge and impact factor. In addition, we derive analytic expressions for the Maxwell tensor components for a Zero-Angular-Momentum-Observer (ZAMO) in the Kerr-Newman-de Sitter spacetime.