https://doi.org/10.1140/epjc/s10052-022-10361-6
Regular Article - Theoretical Physics
Remarks on the black hole shadows in Kerr-de Sitter space times
1
PPGCosmo, CCE, Universidade Federal do Espírito Santo (UFES), Av. Fernando Ferrari, 540, CEP 29.075-910, Vitória, ES, Brazil
2
Núcleo Cosmo-ufes and Departamento de Física, Universidade Federal do Espírito Santo (UFES), Av. Fernando Ferrari, 540, CEP 29.075-910, Vitória, ES, Brazil
3
National Research Nuclear University MEPhI, Kashirskoe sh. 31, 115409, Moscow, Russia
4
Departamento de Física, Universidade Federal de Ouro Preto (UFOP), Campus Universitário Morro do Cruzeiro, 35.400-000, Ouro Preto, Brazil
a
eunice.m.omwoyo@aims-senegal.org
Received:
24
February
2022
Accepted:
22
April
2022
Published online:
3
May
2022
This work is geared towards analysis of shadows cast by Kerr-de Sitter (KdS) and Kerr-de Sitter Revisited (RKdS) black holes. Considering observers in the vicinity of the static radius, we derive the impact parameters defining the apparent positions of the shadows. Such observers are of interest to our work because embedding diagrams have shown that de Sitter space-time is analogous to an asymptotically flat one in the vicinity of the static radius. We also perform a comparative analysis between our result with that in Ref. [1]. Furthermore, we numerically obtain the radii of curvature, vertical diameters and horizontal diameters of the shadows. We find that for 
, M87* observations cannot distinguish a RKdS black hole shadow from that of a Kerr black hole. Additionally, for the same value of 
, KdS and RKdS black hole shadows are, in practise, indistinguishable. Previously, it has also been shown that when 
, KdS and Kerr black hole shadows are indistinguishable. Utilizing the 2017 EHT observations of M87* on the allowed range of the characteristic radius of the shadow, we obtain constraints on both black holes. When, 
, we observe that large angles of inclination (
) do not pass the constraints for both KdS and RKdS black holes.
© The Author(s) 2022
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