Double Spin

As binary black holes (BBHs) spiral inward towards merger, both spin angular momenta precess. This problem has long been simulated and explored numerically, and even solved when only one object has significant spin. When both objects have significant spin, however, the coupled nonlinear ODEs had been analytically intractable.

Astronomers and gravitational wave physicsts are deeply and broadly interested in carefully modeling how BBH spins precess

• Gravitational wave astronomers want to understand how to interpret the rich signal produced by the precession of stellar-mass BBHs’ spins during the late stages of inspiral

• Extragalactic astronomers want to model the evolution of supermassive black holes, which merge repeatedly with companions as their host galaxies collide. At merger, the supermassive binary black hole radiates gravitational waves generally asymmetrically, causing recoil. Though the recoil strength depends precisely on the spin orientations at merger, occasionally the recoil can be strong enough to eject the remnant from its host galaxy.

In a recent study, we found a new semianalytic solution to this problem, providing new insight and faster computation for long-term spin evolution.

For experts : For relativists, our paper uses a known constant of motion of the 2PN orbit-averaged spin precession equations to solve for conservative motion, then combines that solution with a geometric ansatz for how the angular momenta evolve on radiation reaction timescales.

For more information, see

Kesden et al 2015: Effective potentials and morphological transitions for binary black-hole spin precession (PRL 114 1103;arxiv:1411.0674)

• My slides from the 2015 Aspen winter conference “Black holes in dense star clusters”

Articles in the popular press:

UT Dallas website, Science Daily, phys.org, Media INAF (in Italian), Astroblogs (in Dutch), Science World Report, Tech Times, SpaceRef, ECN, R&D, The Daily Galaxy