Evolution of circumbinary accretion disk around supermassive binary black hole: post-Newtonian hydrodynamics versus Newtonian hydrodynamics

TL;DR

This study compares the evolution of circumbinary accretion disks around supermassive binary black holes using post-Newtonian versus Newtonian hydrodynamics, revealing significant differences in gap width that could impact observable signatures.

Contribution

It introduces post-Newtonian hydrodynamics into accretion disk simulations, highlighting differences from Newtonian models in gap formation around supermassive binary black holes.

Findings

Post-Newtonian simulations show wider gaps than Newtonian ones.

Gap width is independent of disk viscosity in post-Newtonian regime.

Potential observable signatures in continuum emission from such systems.

Abstract

We study the evolution of accretion disk around a supermassive binary black hole with equal mass using non-relativistic hydrodynamical simulations performed with FARGO3D. Compared with previous studies with the Newtonian hydrodynamics, here, we adopt the post-Newtonian hydrodynamics using the near zone metric of the binary black hole. In contrast to the Newtonian investigation, we find that there is a dramatic difference in the post-Newtonian regime, gap formed by the circumbinary accretion disk around the binary with equal mass is wider with the post-Newtonian hydrodynamics than that with the Newtonian hydrodynamics and is independent of disk viscosity given that hydrodynamical simulations are run for about the same factor times the viscous timescale associated with different viscosities. This may present unique observable signatures of the continuum emission in such binary-disk system.