# Innermost stable circular orbits in Majumdar--Papapetrou dihole spacetime

## TL;DR

This paper analyzes the stable circular orbits around a dihole spacetime, revealing how orbit stability and radii depend on the separation between black holes, including phenomena like bifurcations and potential formation of double accretion disks.

## Contribution

It classifies the behavior of stable circular orbits in Majumdar--Papapetrou dihole spacetime into five ranges based on separation, identifying critical values and orbit transitions.

## Key findings

- Sequence bifurcates for large separation
- Double accretion disk formation is possible
- Innermost stable orbit radius shows discontinuous transition

## Abstract

We investigate the positions of stable circular massive particle orbits in the Majumdar--Papapetrou dihole spacetime with equal mass. In terms of qualitative differences of their sequences, we classify the dihole separation into five ranges and find four critical values as the boundaries. When the separation is relatively large, the sequence on the symmetric plane bifurcates, and furthermore, they extend to each innermost stable circular orbit in the vicinity of each black hole. In a certain separation range, the sequence on the symmetric plane separates into two parts. On the basis of this phenomenon, we discuss the formation of double accretion disks with a common center. Finally, we clarify the dependence of the radii of marginally stable circular orbits and innermost stable circular orbits on the separation parameter. We find a discontinuous transition of the innermost stable circular orbit radius. We also find the separation range at which the radius of the innermost stable circular orbit can be smaller than that of the stable circular photon orbit.