Eccentricity evolution of compact binaries and applications to gravitational-wave physics. (arXiv:2010.15151v4 [gr-qc] UPDATED)
<a href="http://arxiv.org/find/gr-qc/1/au:+Cardoso_V/0/1/0/all/0/1">Vitor Cardoso</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Macedo_C/0/1/0/all/0/1">Caio F. B. Macedo</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Vicente_R/0/1/0/all/0/1">Rodrigo Vicente</a>
Searches for gravitational waves from compact binaries focus mostly on
quasi-circular motion, with the rationale that wave emission circularizes the
orbit. Here, we study the generality of this result, when astrophysical
environments (e.g., accretion disks) or other fundamental interactions are
taken into account. We are motivated by possible electromagnetic counterparts
to binary black hole coalescences and orbits, but also by the possible use of
eccentricity as a smoking-gun for new physics. We find that: i) backreaction
from radiative mechanisms, including scalars, vectors and gravitational waves
circularize the orbital motion. ii) by contrast, environmental effects such as
accretion and dynamical friction increase the eccentricity of binaries. Thus,
it is the competition between radiative mechanisms and environmental effects
that dictates the eccentricity evolution. We study this competition within an
adiabatic approach, including gravitational radiation and dynamical friction
forces. We show that that there is a critical semi-major axis below which
gravitational radiation dominates the motion and the eccentricity of the system
decreases. However, the eccentricity inherited from the environment-dominated
stage can be substantial, and in particular can affect LISA sources. We provide
examples for GW190521-like sources.
Searches for gravitational waves from compact binaries focus mostly on
quasi-circular motion, with the rationale that wave emission circularizes the
orbit. Here, we study the generality of this result, when astrophysical
environments (e.g., accretion disks) or other fundamental interactions are
taken into account. We are motivated by possible electromagnetic counterparts
to binary black hole coalescences and orbits, but also by the possible use of
eccentricity as a smoking-gun for new physics. We find that: i) backreaction
from radiative mechanisms, including scalars, vectors and gravitational waves
circularize the orbital motion. ii) by contrast, environmental effects such as
accretion and dynamical friction increase the eccentricity of binaries. Thus,
it is the competition between radiative mechanisms and environmental effects
that dictates the eccentricity evolution. We study this competition within an
adiabatic approach, including gravitational radiation and dynamical friction
forces. We show that that there is a critical semi-major axis below which
gravitational radiation dominates the motion and the eccentricity of the system
decreases. However, the eccentricity inherited from the environment-dominated
stage can be substantial, and in particular can affect LISA sources. We provide
examples for GW190521-like sources.
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