scholarly journals Kerr black hole surrounded by a cloud of strings and its weak gravitational lensing in Rastall gravity

2021 ◽  
Vol 104 (10) ◽  
Author(s):  
Zonghai Li ◽  
Tao Zhou
Keyword(s):  
Black Hole ◽  
Gravitational Lensing ◽  
Kerr Black Hole ◽  
Weak Gravitational Lensing

scholarly journals Exploring higher order images with Fe Kα-lines from relativistic disks: black hole spin determination and bias

2021 ◽  
Author(s):  
M Falanga ◽  
P Bakala ◽  
R La Placa ◽  
V De Falco ◽  
A De Rosa ◽  
...  
Keyword(s):  
Black Hole ◽  
Line Profile ◽  
Gravitational Lensing ◽  
Kerr Black Hole ◽  
Higher Order ◽  
Large Area ◽  
X Ray ◽  
Area Detector ◽  
Black Hole Spin ◽  
Stable Circular Orbit

Abstract We study the contributions to the relativistic Fe Kα line profile from higher order images (HOIs) produced by strongly deflected rays from the disk which cross the plunging region, located between the innermost stable circular orbit (ISCO) radius and the event horizon of a Kerr black hole. We investigate the characteristics features imprinted by the HOIs in the line profile for different black hole spins, disk emissivity laws and inclinations. We find that they extend from the red wing of the profile up to energies slightly lower than those of the blue peak, adding ∼0.4 − 1.3 per cent to the total line flux. The contribution to the specific flux is often in the ∼1 per cent to 7 per cent range, with the highest values attained for low and negative spin (a ≲ 0.3) black holes surrounded by intermediate inclination angle (i ∼ 40○) disks. We simulate future observations of a black hole X-ray binary system with the Large Area Detector of the planned X-ray astronomy enhanced X-ray Timing and Polarimetry Mission (eXTP) and find that the Fe Kα line profiles of systems accreting at ≲ 1 per cent the Eddington rate are affected by the HOI features for a range of parameters. This would provide evidence of the extreme gravitational lensing of HOI rays. Our simulations show also that not accounting for HOI contributions to the Fe Kα line profile may systematically bias measurements of the black hole spin parameter towards values higher by up to ∼0.3 than the inputted ones.

Strong gravitational lensing by Kerr–Newman-Nut-Quintessence black hole

2021 ◽  
Author(s):  
Niyaz Uddin Molla ◽  
Ujjal Debnath
Keyword(s):  
Black Hole ◽  
Equatorial Plane ◽  
Gravitational Lensing ◽  
Deflection Angle ◽  
Null Geodesic ◽  
Kerr Black Hole ◽  
Eos Parameter ◽  
Strong Gravitational Lensing ◽  
Spin Parameter ◽  
The Deflection Angle

We investigate the strong gravitational lensing on equatorial plane as well as quasi-equatorial plane by the Kerr–Newman-Nut-Quintessence (KNNQ) black hole (BH) with the equation of state (EoS) parameter of the quintessence [Formula: see text] and the quintessence density [Formula: see text]. Our results show that the strong gravitational lensing in the KNNQ black hole space–time has some distinct behaviors from those in the backgrounds of the four dimension Kerr black hole. Also, we investigate the strong gravitational lensing on equatorial plane as well as quasi-equatorial plane by the KNNQ BH with the effects of Nut charge, spin parameter and quintessence parameter. First, we calculate the null geodesic equations using the Hamilton–Jacobi separation method. Then we investigate the equatorial lensing by KNNQ black hole. We obtain the deflection angle and deflection coefficients in the equatorial plane, which is affected by EoS parameter of the quintessence [Formula: see text], quintessence density [Formula: see text], Nut parameter [Formula: see text], spin parameter [Formula: see text] and quintessence parameter [Formula: see text] [Formula: see text]. Next, we discuss the lens equation and the observables in the equatorial plane. Finally, we investigate gravitational lensing by the KNNQ black hole in the quasi-equatorial plane. In this work, the quintessence density [Formula: see text], the EoS parameter of the quintessence [Formula: see text], Nut parameter [Formula: see text], spin parameter [Formula: see text] and quintessence parameter [Formula: see text] [Formula: see text] have significant effects on the strong gravitational lensing both in equatorial plane as well as quasi-equatorial plane.

scholarly journals Weak gravitational lensing by Einstein-nonlinear-Maxwell–Yukawa black hole

2020 ◽  
Vol 17 (12) ◽  
pp. 2050182
Author(s):  
Wajiha Javed ◽  
Muhammad Bilal Khadim ◽  
Ali Övgün
Keyword(s):  
Black Hole ◽  
Gravitational Lensing ◽  
Gaussian Curvature ◽  
Deflection Angle ◽  
Weak Field ◽  
Plasma Medium ◽  
Weak Gravitational Lensing ◽  
The Deflection Angle ◽  
Bonnet Theorem

In this paper, we analyze the weak gravitational lensing in the context of Einstein-nonlinear-Maxwell–Yukawa black hole. To this desire, we derive the deflection angle of light by Einstein-nonlinear-Maxwell–Yukawa black hole using the Gibbons and Werner method. For this purpose, we obtain the Gaussian curvature and apply the Gauss–Bonnet theorem to find the deflection angle of Einstein-nonlinear-Maxwell–Yukawa black hole in weak field limits. Moreover, we derive the deflection angle of light in the influence of plasma medium. We also analyze the graphical behavior of deflection angle by Einstein-nonlinear-Maxwell–Yukawa black hole in the presence of plasma as well as non-plasma medium.

scholarly journals Weak Gravitational Lensing by Horndeski Theory Using the Gauss-Bonnet Theorem

2020 ◽  
Author(s):  
Wajiha Javed ◽  
Jameela Abbas ◽  
Yashmitha Kumaran ◽  
Ali Övgün
Keyword(s):  
Black Hole ◽  
Gravitational Lensing ◽  
Deflection Angle ◽  
Field Approximation ◽  
Weak Field ◽  
Plasma Medium ◽  
Weak Gravitational Lensing ◽  
The Deflection Angle ◽  
Bonnet Theorem ◽  
The Impact

The main goal of this paper is to study the weak gravitational lensing by Horndeski black hole in weak field approximation. In order to do so, we exploit the Gibbons-Werner method to the optical geometry of Horndeski black hole and implement the Gauss-Bonnet theorem to accomplish the deflection angle of light in weak field region. Furthermore, we have endeavored to extend the scale of our work by comprising the impact of plasma medium on the deflection angle as properly. Later, the graphical influence of the deflection angle of photon on Horndeski black hole in plasma and non-plasma medium is examined.

scholarly journals Weak Gravitational Lensing by Einstein-Non-Linear-Maxwell-Yukawa Black Hole

2020 ◽  
Author(s):  
Wajiha Javed ◽  
Muhammad Bilal Khadim ◽  
Ali Övgün
Keyword(s):  
Black Hole ◽  
Gravitational Lensing ◽  
Deflection Angle ◽  
Plasma Medium ◽  
Weak Gravitational Lensing ◽  
Non Linear ◽  
The Deflection Angle ◽  
Bonnet Theorem

In this article, we analyze the weak gravitational lensing in the context of Einstein-non-linear Maxwell-Yukawa black hole. To this desire, we derive the deflection angle of light by Einstein-non-linear Maxwell-Yukawa black hole using the Gibbons and Werner method. For this purpose, we obtain the Gaussian optical curvature and implement the Gauss-Bonnet theorem to investigate the deflection angle of Einstein-non-linear Maxwell-Yukawa black hole. Moreover, we derive the deflection angle of light in the presence of plasma medium. We also analyze the graphical behavior of deflection angle by Einstein-non-linear Maxwell-Yukawa black hole in the presence of plasma as well as non-plasma medium.

scholarly journals Weak gravitational lensing by Kerr-MOG black hole and Gauss–Bonnet theorem

2019 ◽  
Vol 411 ◽  
pp. 167978 ◽  
Author(s):  
Ali Övgün ◽  
İzzet Sakallı ◽  
Joel Saavedra
Keyword(s):  
Black Hole ◽  
Gravitational Lensing ◽  
Weak Gravitational Lensing ◽  
Bonnet Theorem
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