Accretion onto a Supermassive Black Hole Binary Before Merger

Understand

While supermassive binary black holes inspiral toward merger they may also experience significant accretion of matter from a surrounding disk.

• We study the dynamics of this system, simultaneously describing the evolving spacetime and magnetized plasma, and present the first relativistic calculation simulating two equal-mass, non-spinning black holes as they inspiral from a $20M$ ($G=c=1$) initial separation almost to merger, $\simeq 9M$ ($M$=binary mass).
• Our dynamical results imply important observational consequences: for instance, the accretion rate $\dot M$ onto the black holes first decreases and then reaches a plateau, dropping by only a factor of $\sim 3$ despite the rapid inspiral.
• An estimated bolometric light curve thus suggests some merging SMBBHs may be quite luminous past the predicted decoupling from the circumbinary disk.