June 6, 2023

Alireza Khesali

Degree: Professor
Address: Department of Physics, Faculty of Basic Sciences,University of Mazandaran
Education: Ph.D in َAstrophysics
Phone: 35343085
Faculty: Faculty of Science


Title More on accreting black hole spacetime in equatorial plane
Type Article
Black Holes Accretion Disks
Researchers khadejeh Salahshoor (First researcher) , Kourosh Nozari (Second researcher) , Alireza Khesali (Third researcher)


Spacetime around an accreting black hole is an interesting issue to study. The metric of an isolated black hole (rotating or non-rotating) spacetime has been well-known for decades. Although metrics of some spacetimes containing accreting black holes are known in some situations, the issue has some faces that are not well-known yet and need further investigation. In this paper, we construct a new form of metric which the effect of accretion disk on black hole spacetime is taken into account in the equatorial plane. We study motion and trajectories of massive particles and also photons falling from infinity towards black hole in equatorial plane around the black hole. We use an exponential form for the density profile of the accretion disk in equatorial plane as ρ=ρ0e−αrρ=ρ0e−αr . We show that with this density profile, the disk is radially stable if α≤3×10−3α≤3×10−3 (in units of length inverse). In order to study some important quantities related to the accretion disks such as locations of marginally stable circular orbits ( rmsrms or rISCOrISCO ), marginally bounded circular orbits (rmb)(rmb) , and also photon orbits in equatorial plane, we use the effective potential approach. We show that in this spacetime metric the innermost stable circular orbit in equatorial plane is given by rISCO=4.03μrISCO=4.03μ (where μ=MGc2μ=MGc2 ) which is different, but comparable, with the Schwarzschild spacetime result, r(Sch)ISCO=6μrISCO(Sch)=6μ . We show that the maximum radiation efficiency of the accretion disk, ηη , in equatorial plane is 8.6 percent which is greater than the corresponding value for Schwarzschild spacetime. Finally, we show that in this setup photons can have stable circular orbits in equatorial plane unlike the Schwarzschild spacetime.