2020/10/31 by Jonathan Zrake, Christopher Tiede, Andrew MacFadyen +1 · 2 citations
Physics and Astronomy · #astro-ph.HE
paper · pdf · doi:10.3847/2041-8213/abdd1c
published as The Astrophysical Journal Letters, Volume 909, Number 1, 2021 March 3 · Published in ApJL
arxiv created 2021/03/04 · arxiv updated 2021/03/05
Using high-resolution hydrodynamics simulations, we show that equal-mass binaries accreting from a circumbinary disk evolve toward an orbital eccentricity of e ≃ 0.45, unless they are initialized on a nearly circular orbit with e \lesssim 0.08, in which case they further circularize. The implied bi-modal eccentricity distribution resembles that seen in post-AGB stellar binaries. Large accretion spikes around periapse impart a tell-tale, quasi-periodic, bursty signature on the light curves of eccentric binaries. We predict that intermediate-mass and massive black hole binaries at z \lesssim 10 entering the LISA band will have measurable eccentricities in the range e ≃ 10-3 - 10-2, if they have experienced a gas-driven phase. On the other hand, GW190521 would have entered the LIGO/Virgo band with undetectable eccentricity ∼ 10-6 if it had been driven into the gravitational wave regime by a gas disk.