Accretion onto a Supermassive Black Hole Binary before Merger
[1];
[2];
[3];
[4];
[5];
[6]
- Univ. of Cambridge (United Kingdom); Rochester Inst. of Technology, Rochester, NY (United States)
- Johns Hopkins Univ., Baltimore, MD (United States)
- Rochester Inst. of Technology, Rochester, NY (United States)
- NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States)
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
- Johns Hopkins Univ., Baltimore, MD (United States); Max Planck Institute for Astrophysics, Garching (Germany)
While supermassive binary black holes (SMBBHs) inspiral toward merger they may also accrete matter from a surrounding disk. To study the dynamics of this system requires simultaneously describing the evolving spacetime and the magnetized plasma. We present the first relativistic calculation simulating two equal-mass, nonspinning black holes as they inspiral from a 20 M (G = c = 1) initial separation almost to merger. Our results imply important observational consequences: for instance, the accretion rate $$\dot{M}$$ onto the black holes first decreases and then plateaus, dropping by only a factor of ~3 despite the rapid inspiral. An estimated bolometric light curve follows the same profile, suggesting some merging SMBBHs may be significantly luminous past the predicted circumbinary disk decoupling. The minidisks are nonstandard: Reynolds, not Maxwell, stresses dominate, and they oscillate between two states. In one part of the cycle, "sloshing" streams transfer mass between minidisks, carrying kinetic energy at a rate sometimes as high as the peak minidisk bolometric luminosity. We also discover that episodic accretion drives time-varying minidisk tilts. These complex dynamics all contribute to unique cyclical behavior in the light curves of late-time inspiraling SMBBHs. The poloidal magnetic flux on the black holes is roughly constant at a dimensionless level $$\phi$$ ~ 2–3, but doubles just before merger; for significant black hole spin, this flux predicts powerful jets with variability driven by binary dynamics, another potentially unique electromagnetic signature. This simulation is the first to employ our multipatch infrastructure PATCHWORKMHD, decreasing the computational expense to ~3% of conventional single-grid methods' cost.
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
- Sponsoring Organization:
- National Science Foundation (NSF); USDOE
- Grant/Contract Number:
- 89233218CNA000001
- OSTI ID:
- 2476029
- Report Number(s):
- LA-UR--23-25008
- Journal Information:
- The Astrophysical Journal, Journal Name: The Astrophysical Journal Journal Issue: 2 Vol. 974; ISSN 0004-637X
- Publisher:
- IOP PublishingCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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