Rapid eccentricity oscillations and the mergers of compact objects in hierarchical triples
Abstract
KozaiLidov (KL) oscillations can accelerate compact object mergers via gravitational wave radiation by driving the inner binaries of hierarchical triples to high eccentricities. We perform direct threebody integrations of highmassratio compact object triple systems using FEWBODY including postNewtonian terms. We find that the inner binary undergoes rapid eccentricity oscillations (REOs) on the timescale of the outer orbital period which drive it to higher eccentricities than secular theory would otherwise predict, resulting in substantially reduced merger times. For a uniform distribution of tertiary eccentricity (e_{2}), ∼40 per cent of systems merge within ∼12 eccentric KL timescales whereas secular theory predicts that only ∼20 per cent of such systems merge that rapidly. This discrepancy becomes especially pronounced at low e_{2}, with secular theory overpredicting the merger time by many orders of magnitude. We show that a nonnegligible fraction of systems have eccentricity >0.8 when they merge, in contrast to predictions from secular theory. Our results are applicable to highmassratio triple systems containing black holes or neutron stars. In objects in which tidal effects are important, such as white dwarfs, stars, and planets, REOs can reduce the tidal circularization timescale by an order of magnitude and bring the components of the inner binary into closer orbits than would be possible in the secular approximation.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 March 2014
 DOI:
 10.1093/mnras/stu039
 arXiv:
 arXiv:1308.5682
 Bibcode:
 2014MNRAS.439.1079A
 Keywords:

 binaries: close;
 stars: kinematics;
 Astrophysics  High Energy Astrophysical Phenomena;
 General Relativity and Quantum Cosmology
 EPrint:
 Accepted to MNRAS. 15 pages, 11 figures