Evolution of a binary black hole with a retrograde circumbinary accretion disk

Journal Article · Wed Jun 10 04:00:00 EDT 2015 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/806/1/88· OSTI ID:22883080

Schnittman, Jeremy D. ^[1]; Krolik, Julian H. ^[2]

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1. NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
2. Department of Physics and Astronomy, Johns Hopkins University, 3400 N Charles Street, Baltimore, MD 21218 (United States)

We consider the evolution of a supermassive black hole binary (SMBHB) surrounded by a retrograde accretion disk. Assuming the disk is exactly in the binary plane and transfers energy and angular momentum to the binary via direct gas accretion, we calculate the time evolution of the binaryʼs semimajor axis a and eccentricity e. Because the gas is predominantly transferred when the binary is at apocenter, we find the eccentricity grows rapidly while maintaining constant a(1+e). After accreting only a fraction of the secondaryʼs mass, the eccentricity grows to nearly unity; from then on, gravitational wave (GW) emission dominates the evolution, preserving constant a(1−e). The high-eccentricity waveforms redistribute the peak GW power from the nHz to μHz bands, substantially affecting the signal that might be detected with pulsar timing arrays. We also estimate the torque coupling binaries of arbitrary eccentricity with obliquely aligned circumbinary disks. If the outer edge of the disk is not an extremely large multiple of the binary separation, retrograde accretion can drive the binary into the GW-dominated state before these torques align the binary with the angular momentum of the mass supply.

• OSTI ID: 22883080
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 806; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United Kingdom
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ACCRETION DISKS
ANGULAR MOMENTUM
AVAILABILITY
BLACK HOLES
EMISSION
GRAVITATIONAL WAVES
MASS
PULSARS
STAR EVOLUTION