Disk-induced Binary Precession: Implications for Dynamics and Multimessenger Observations of Black Hole Binaries

Abstract

Many studies have recently documented the orbital response of eccentric binaries accreting from thin circumbinary disks, characterizing the change in the binary semimajor axis and eccentricity. We extend these calculations to include the precession of the binary’s longitude of periapse induced by the circumbinary disk, and we characterize this precession continuously with binary eccentricity e b for equal mass components. This disk-induced apsidal precession is prograde with a weak dependence on the binary eccentricity when e b ≲ 0.4 and decreases approximately linearly for e b ≳ 0.4; yet at all e b binary precession is faster than the rates of change to the semimajor axis and eccentricity by an order of magnitude. We estimate that such precession effects are likely most important for subparsec separated binaries with masses ≲107 M ⊙, like LISA precursors. We find that accreting, equal-mass LISA binaries with M < 106 M ⊙ (and the most massive M ∼ 107 M ⊙ binaries out to z ∼ 3) may acquire a detectable phase offset due to the disk-induced precession. Moreover, disk-induced precession can compete with general relativistic precession in a vacuum, making it important for observer-dependent electromagnetic searches for accreting massive binaries—like Doppler boost and binary self-lensing models—after potentially only a few orbital periods.