Accretion disks around black holes in modified strong gravity

Abstract

Context. Stellar-mass black holes offer what is perhaps the best scenario to test theories of gravity in the strong-field regime. In particular, f (R) theories, which have been widely discus in a cosmological context, can be constrained through realistic astrophysical models of phenomena around black holes. Aims. We aim at building radiative models of thin accretion disks for both Schwarzschild and Kerr black holes in f (R) gravity. Methods. We study particle motion in f (R)-Schwarzschild and Kerr space-times.Results. We present the spectral energy distribution of the accretion disk around constant Ricci scalar f (R) black holes, and constrain specific f (R) prescriptions using features of these systems.Conclusions. A precise determination of both the spin and accretion rate onto black holes along with X-ray observations of their thermal spectrum might allow to identify deviations of gravity from general relativity. We use recent data on the high-mass X-ray binary Cygnus X-1 to restrict the values of the parameters of a class of f (R) models.

Kerr geometry in $$f(T)$$ f ( T ) gravity

“…We remark that different aspects of rotating black holes have been discussed in the context of TEGR [27][28][29][30][31]. Among the papers about Kerr spacetime in modified gravity, we can mention those referred to f (R) gravity [32][33][34][35]. Other rotating geometries, like the Gödel universe [36], have also been studied in TEGR [37,38], as well as in f (R) theories of gravity in both metric and Palatini approaches [39][40][41].…”

Photon motion in Kerr–de Sitter spacetimes

“…(37); -case X = −a now corresponds to vortical motion above the poles -the inner cones have coalesced with the spin axis, the outer ones stay open; -the vortical motion exists as in the previous cases and above that for −a < X < X θ max(+) ; • q = 0 (Fig. 2l) -the definition (48) holds, the functions X θ +(−) (m; q, y, a) are defined at 0, 1 ( 0, 1 \ {m d }); the values for m = 0 are given by (50), but now…”

“…It is worth to note that the SdS and KdS spacetimes are equivalent to some solutions of the f (R) gravity representing black holes and naked singularities [50,88].…”

Silhouette and spectral line profiles in the special modification of the Kerr black hole geometry generated by quintessential fields

“…There is a large variety of research related to the braneworld models [1][2][3]13,24,33,37,38,40,48], standard gravity combined with the non-linear electrodynamics giving regular black holes or no-horizon spacea e-mail: jan.schee@fpf.slu.cz b e-mail: zdenek.stuchlik@fpf.slu.cz times [4,5,7,39,52,57], Hořava quantum gravity [18,22,50,51,59], String theory [36], f (R) gravity [34,42], Kerr geometry modified by the cosmological constant [11,17,17,21,[25][26][27][28]32,35,41,[44][45][46][47]49,[53][54][55], or quintessential fields [14,23,58], higher-dimensional spacetimes [17], or in the case of Einstein gravity coupled to a complex, scalar field …”