Zoom-Whirl Orbits in Black Hole Binaries

TL;DR

This paper demonstrates through numerical relativity that zoom-whirl orbits in black hole binaries are more common than previously thought, especially with larger mass ratios and spins, affecting gravitational wave signals.

Contribution

It provides the first evidence of zoom-whirl behavior persisting despite gravitational radiation dissipation in generic black hole binary orbits.

Findings

Zoom-whirl behavior occurs in a wider range of parameters than expected.

Larger mass ratios and spins increase the duration and prominence of zoom-whirl phases.

Eccentric orbits can merge during whirl phases, affecting gravitational wave signatures.

Abstract

Zoom-whirl behavior has the reputation of being a rare phenomenon. The concern has been that gravitational radiation would drain angular momentum so rapidly that generic orbits would circularize before zoom-whirl behavior could play out, and only rare highly tuned orbits would retain their imprint. Using full numerical relativity, we catch zoom-whirl behavior despite dissipation. The larger the mass ratio, the longer the pair can spend in orbit before merging and therefore the more zooms and whirls seen. Larger spins also enhance zoom-whirliness. An important implication is that these eccentric orbits can merge during a whirl phase, before enough angular momentum has been lost to truly circularize the orbit. Waveforms will be modulated by the harmonics of zoom-whirls, showing quiet phases during zooms and louder glitches during whirls.