TY  - JOUR
AU  - Olmo, G. J.
AU  - Rosa, J. L.
AU  - Rubiera-Garcia, D.
AU  - Saez-Chillon Gomez, D.
PY  - 2023
DA  - 2023//
TI  - Shadows and photon rings of regular black holes and geonic horizonless compact objects
T2  - Class. Quantum Gravity
JO  - Classical and Quantum Gravity
SP  - 174002
EP  - 37pp
VL  - 40
IS  - 17
PB  - IOP Publishing Ltd
KW  - black holes
KW  - compact objects
KW  - photon rings
KW  - shadows
KW  - metric-affine gravity
KW  - Born-Infeld gravity
KW  - regular solutions
AB  - The optical appearance of a body compact enough to feature an unstable bound orbit, when surrounded by an accretion disk, is expected to be dominated by a luminous ring of radiation enclosing a central brightness depression typically known as the shadow. Despite observational limitations, the rough details of this picture have been now confirmed by the results of the Event Horizon Telescope (EHT) Collaboration on the imaging of the M87 and Milky Way supermassive central objects. However, the precise characterization of both features-ring and shadow-depends on the interaction between the background geometry and the accretion disk, thus being a fertile playground to test our theories on the nature of compact objects and the gravitational field itself in the strong-field regime. In this work we use both features in order to test a continuous family of solutions interpolating between regular black holes and horizonless compact objects, which arise within the Eddington-inspired Born-Infeld theory of gravity, a viable extension of Einstein's general relativity (GR). To this end we consider seven distinctive classes of such configurations (five black holes and two traversable wormholes) and study their optical appearances under illumination by a geometrically and optically thin accretion disk, emitting monochromatically with three analytic intensity profiles previously suggested in the literature. We build such images and consider the sub-ring structure created by light rays crossing the disk more than once and existing on top of the main ring of radiation. We discuss in detail the modifications as compared to their GR counterparts, the Lyapunov exponents of unstable nearly-bound orbits, as well as the differences between black hole and traversable wormholes for the three intensity profiles. In addition we use the claim by the EHT Collaboration on the radius of the bright ring acting (under proper calibrations) as a proxy for the radius of the shadow itself to explore the parameter space of our solutions compatible with such a result.
SN  - 0264-9381
UR  - https://arxiv.org/abs/2302.12064
UR  - https://doi.org/10.1088/1361-6382/aceacd
DO  - 10.1088/1361-6382/aceacd
LA  - English
N1  - WOS:001043720300001
ID  - Olmo_etal2023
ER  -