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Binary black hole mergers from field triples: properties, rates, and the impact of stellar evolution

Antonini, Fabio, Toonen, Silvia and Hamers, Adrian S. 2017. Binary black hole mergers from field triples: properties, rates, and the impact of stellar evolution. Astrophysical Journal 841 (2) , 77. 10.3847/1538-4357/aa6f5e

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Abstract

We consider the formation of binary black hole (BH) mergers through the evolution of field massive triple stars. In this scenario, favorable conditions for the inspiral of a BH binary are initiated by its gravitational interaction with a distant companion, rather than by a common-envelope phase invoked in standard binary evolution models. We use a code that follows self-consistently the evolution of massive triple stars, combining the secular triple dynamics (Lidov–Kozai cycles) with stellar evolution. After a BH triple is formed, its dynamical evolution is computed using either the orbit-averaged equations of motion, or a high-precision direct integrator for triples with weaker hierarchies for which the secular perturbation theory breaks down. Most BH mergers in our models are produced in the latter non-secular dynamical regime. We derive the properties of the merging binaries and compute a BH merger rate in the range (0.3–1.3) Gpc−3 yr−1, or up to ≈2.5 Gpc−3 yr−1 if the BH orbital planes have initially random orientation. Finally, we show that BH mergers from the triple channel have significantly higher eccentricities than those formed through the evolution of massive binaries or in dense star clusters. Measured eccentricities could therefore be used to uniquely identify binary mergers formed through the evolution of triple stars. While our results suggest up to ≈10 detections per year with Advanced-LIGO, the high eccentricities could render the merging binaries harder to detect with planned space based interferometers such as LISA.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Publisher: American Astronomical Society
ISSN: 0004-637X
Date of First Compliant Deposit: 4 February 2020
Date of Acceptance: 19 April 2017
Last Modified: 14 Sep 2020 10:39
URI: http://orca.cardiff.ac.uk/id/eprint/129320

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