Gravitational weak lensing by black hole in Horndeski gravity in presence of plasma

Self Cite

In this work we have investigated the gravitational weak lensing and shadow of the Ellis-Bronnikov wormhole. First, we have studied the photon motion in plasma medium and wormhole shadow. It has been shown that the radius of the photon sphere of the Ellis-Bronnikov wormhole and the size of the wormhole shadow becomes larger under the influence of the parameter $a$. The upper limit of the parameter $a$ in the Ellis-Bronnikov wormhole spacetime has been obtained. Second, we have investigated the weak gravitational lensing for the Ellis-Bronnikov wormhole and have calculated the deflection angle for uniform and non uniform plasma cases. It has been shown that the value of the deflection angle for uniform plasma increased with the increase of the plasma parameter and for non uniform plasma vice versa. It has been also indicated that under influence of the parameter $a$ the values of the deflection angles for two cases are decreased. Finally, we have investigated the magnification of image brightness using the deflection angle of the light rays around the wormhole in Ellis-Bronnikov theory.

Section: Introductionmentioning

confidence: 99%

Shadow and weak gravitational lensing for Ellis-Bronnikov wormhole*

Alloqulov,

Atamurotov,

Abdujabbarov

et al. 2024

Self Cite

“…The influence of a uniform plasma on weak gravitational lensing by a spherically symmetric BH in a modified gravity theory has been investigated in Refs. [135][136][137][138][139][140][141][142][143][144][145][146]. Some other recent interesting works relating the effects of plasma on the optical properties of BHs in Einstein gravity and other theories of gravity can be found in literature [147][148][149][150][151][152].…”

Section: Introductionmentioning

confidence: 99%

Weak deflection angle and shadow cast by the charged-Kiselev black hole with cloud of strings in plasma*

Atamurotov

Hussain²,

Mustafa³

et al. 2023

Self Cite

In this work, the gravitational deflection angle of photon in the weak field limit (or the weak deflection angle) and shadow cast by the electrically charged and spherically symmetric static Kiselev black hole (BH) in the string cloud background are investigated. The influence of the BH charge $Q$, the quintessential parameter $\gamma$ and the string cloud parameter $a$ is studied on the weak deflection angle using the Gauss-Bonnet theorem, on the radius of photon spheres and on the size of the BH shadow in the spacetime geometry of the charged-Kiselev BH in string clouds. Moreover, we study the effects of plasma (uniform and non-uniform) on the weak deflection angle and on the shadow cast by the charged-Kiselev BH surrounded by the clouds of strings. In the presence of uniform/nonuniform plasma medium, increase in the cloud of string parameter $a$, increases the deflection angle $\alpha$. On the other hand decrease in the BH charge $Q$, decreases the deflection angle. Further we observe that an increase of the BH charge $Q$ causes a decrease in the size of the shadow of the BH. We notice that with increase in the values of the parameters $\gamma$ and $a$, the size of the BH shadow also increases and therefore the intensity of the gravitational field around the charged-Kiselev BH in string clouds increases. Thus the gravitational field of the charged-Kiselev BH in string cloud background would be stronger than the field produced by the pure Reissner-Nordstrom BH. Moreover, we use the data released by the Event Horizon Telescope (EHT) collaboration, for the supermassive BHs M87* and Sgr A*, to obtain constraints on the values of the parameters $\gamma$ and $a$.

“…These authors not only studied gravitational lensing and BH shadows in the presence of plasma but also investigated plasma accretion in the radial infall of the BH. In the literature, plasma effects on the shadows of diverse modified gravity BHs have been vigorously investigated for phenomenological reasons [15][16][17][18][19][20][21][22][23], along with gravitational weak lensing in the presence of plasma [24][25][26][27][28][29][30][31][32][33][34]. Previously, gravitational lensing in the weak and strong field regimes in the vacuum surrounding BHs has been reported by some authors in Refs.…”

Section: Introduction R −Nmentioning

confidence: 99%

Quantum effects on the black hole shadow and deflection angle in the presence of plasma*

Atamurotov¹,

Jamil²,

Jusufi³

2023

Self Cite

In this paper, optical properties of renormalization group improved (RGI) Schwarzschild black hole (BH) are investigated in plasma medium. Starting from the equations of motions in plasma medium, we have shown how the shadow radius of the RGI black hole is modified. To this end, we have computed the deflection angle of light in the weak gravity regime for uniform and non-uniform plasma medium. Importantly, due to the plasma medium, we find that the equations of motions for light obtained from the radiating and infalling/rest gas has to be modified. This in turn, changes and modifies the expression for the intensity observed far away from the black hole. Finally, we have obtained the shadow images for the RGI black hole for different plasma models. Even thought, quantum effect changes the background geometry, these effects are very small and, practically, it is impossible to detect them with the present technology using the supermassive black hole shadows. The parameter $\Omega$ encodes the quantum effects and, in principle, one expects such quantum effects to play a significant role only for very small black holes. On the other hand, the effect of plasma medium can play important role on the optical appearance of black holes since they effect and modify the equations of motions.