Resolving the relative influence of strong field spacetime dynamics and MHD on circumbinary disk physics

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In this paper we evolve magnetized and unmagnetized circumbinary accretion disks around supermassive black hole binaries in the relativistic regime.

• We use a post-Newtonian expansion to construct an analytical spacetime and determine how the order of the post-Newtonian (PN) expansion affects the dynamics of the gas.
• We find very small differences in the late-time bulk dynamics of non-magnetized hydrodynamic evolutions between the two spacetimes down to separations of approximately $40GM/c^2$ where $M$ is the total mass of the binary.
• For smaller separations, the differences due to PN-order become comparable to differences caused by using initial data further from equilibrium.