https://doi.org/10.1140/epjc/s10052-021-09623-6
Regular Article - Theoretical Physics
The evolutions of the innermost stable circular orbits in dynamical spacetimes
Department of Modern Physics, University of Science and Technology of China, 230026, Hefei, Anhui, China
Received:
26
June
2021
Accepted:
6
September
2021
Published online:
5
October
2021
In this paper, we studied the evolutions of the innermost stable circular orbits (ISCOs) in dynamical spacetimes. At first, we reviewed the method to obtain the ISCO in Schwarzschild spacetime by varying its conserved orbital angular momentum. Then, we demonstrated this method is equivalent to the effective potential method in general static and stationary spacetimes. Unlike the effective potential method, which depends on the presence of the conserved orbital energy, this method requires the existence of conserved orbital angular momentum in spacetime. So it can be easily generalized to the dynamical spacetimes where there exists conserved orbital angular momentum. From this generalization, we studied the evolutions of the ISCOs in Vaidya spacetime, Vaidya-AdS spacetime and the slow rotation limit of Kerr–Vaidya spacetime. The results given by these examples are all reasonable and can be compared with the evolutions of the photon spheres in dynamical spacetimes.
© The Author(s) 2021
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