Gravitational wave diagnosis of a circumbinary disk
Abstract
When binary black holes are embedded in a gaseous environment, a rotating disk surrounding them, the so-called circumbinary disk, will be formed. The binary exerts a gravitational torque on the circumbinary disk and thereby transfers its orbital angular momentum to it, while the angular momentum of the circumbinary disk is transferred to the binary through mass accretion. The binary undergoes an orbital decay due to both gravitational wave emission and binary-disk interaction, driving the phase evolution of the gravitational wave signal. The precise measurement of the gravitational wave phase may therefore provide information regarding the circumbinary disk. In this paper, we assess the detectability of this signature of binary-disk interaction using future spaceborne gravitational wave detectors such as DECIGO and BBO, via standard matched filtering analysis. We find that the effect of the circumbinary disk around binary black holes in the mass range 6M⊙≤M≲3×103M⊙ is detectable at a statistically significant level in five years of observation, provided that gas accretes onto the binary at a rate greater than M˙∼1.4×1017[gs-1]j-1(M/10M⊙)33/23 with 10% mass-to-energy conversion efficiency, where j represents the efficiency of the angular momentum transfer from the binary to the circumbinary disk. We point out that the circumbinary disk is detectable, even if its mass around the inner edge is over 10 orders of magnitude less than the binary mass. We show that O(0.1) coalescence events for binary stellar-mass black holes are expected to occur in sufficiently dense molecular clouds during five years of observation, and we discuss the event rate for binary intermediate-mass black holes in spite of their large uncertainties. Since the expected number of merger events for binary stellar-mass black holes is also proportional to the binary’s bulk velocity to the power of -27/5, the resultant coalescence events can be easily reduced by 1 order of magnitude even when the bulk velocity is twice larger than the fiducial one, 20kms-1. The feasibility of detection of circumbinary disks around binary stellar-mass black holes is significantly low, even with five years of observation with DECIGO/BBO.
- Publication:
-
Physical Review D
- Pub Date:
- February 2013
- DOI:
- 10.1103/PhysRevD.87.044051
- arXiv:
- arXiv:1201.2858
- Bibcode:
- 2013PhRvD..87d4051H
- Keywords:
-
- 04.25.dg;
- 04.30.-w;
- 95.85.Sz;
- 97.10.Gz;
- Numerical studies of black holes and black-hole binaries;
- Gravitational waves: theory;
- Gravitational radiation magnetic fields and other observations;
- Accretion and accretion disks;
- Astrophysics - Cosmology and Extragalactic Astrophysics;
- General Relativity and Quantum Cosmology
- E-Print:
- 10 pages, 2 figures, submitted to ApJ