Zoom-Whirl Orbits in Black Hole Binaries
by Healy, James and Levin, Janna and Shoemaker, Deirdre
Zoom-whirl behavior has the reputation of being a rare phenomenon in comparable mass binaries. 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 for a range of orbits. The larger the mass ratio, the longer the pair can spend in orbit before merging and therefore the more zooms and whirls that can be 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. In other words, although the whirl phase is nearly circular, merger of eccentric orbits occurs through a separatrix other than the isco. Gravitational waveforms from eccentric binaries will be modulated by the harmonics of zoom-whirl orbits, showing quiet phases during a zoom and louder glitches during whirls.
