Eccentric Black Hole Mergers in Dense Star Clusters: The Role of Binary-Binary Encounters. (arXiv:1810.00901v4 [astro-ph.HE] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Zevin_M/0/1/0/all/0/1">Michael Zevin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Samsing_J/0/1/0/all/0/1">Johan Samsing</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rodriguez_C/0/1/0/all/0/1">Carl Rodriguez</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Haster_C/0/1/0/all/0/1">Carl-Johan Haster</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ramirez_Ruiz_E/0/1/0/all/0/1">Enrico Ramirez-Ruiz</a>
We present the first systematic study of strong binary-single and
binary-binary black hole interactions with the inclusion of general relativity.
When including general relativistic effects in strong encounters, dissipation
of orbital energy from gravitational waves (GWs) can lead to captures and
subsequent inspirals with appreciable eccentricities when entering the
sensitive frequency ranges of the LIGO and Virgo GW detectors. In this study,
we perform binary-binary and binary-single scattering experiments with general
relativistic dynamics up through the 2.5 post-Newtonian order included, both in
a controlled setting to gauge the importance of non-dissipative post-Newtonian
terms and derive scaling relations for the cross-section of GW captures, as
well as experiments tuned to the strong interactions from state-of-the art
globular cluster models to assess the relative importance of the binary-binary
channel at facilitating GW captures and the resultant eccentricity
distributions of inspiral from channel. Although binary-binary interactions are
10-100 times less frequent in globular clusters than binary-single
interactions, their longer lifetime and more complex dynamics leads to a higher
probability for GW captures to occur during the encounter. We find that
binary-binary interactions contribute 25-45% of the eccentric mergers which
occur during strong black hole encounters in globular clusters, regardless of
the properties of the cluster environment. The inclusion of higher multiplicity
encounters in dense star clusters therefore have major implications on the
predicted rates of highly eccentric binaries potentially detectable by the
LIGO/Virgo network. As gravitational waveforms of eccentric inspirals are
distinct from those generated by merging binaries which have circularized,
measurements of eccentricity in such systems would highly constrain their
formation scenario.
We present the first systematic study of strong binary-single and
binary-binary black hole interactions with the inclusion of general relativity.
When including general relativistic effects in strong encounters, dissipation
of orbital energy from gravitational waves (GWs) can lead to captures and
subsequent inspirals with appreciable eccentricities when entering the
sensitive frequency ranges of the LIGO and Virgo GW detectors. In this study,
we perform binary-binary and binary-single scattering experiments with general
relativistic dynamics up through the 2.5 post-Newtonian order included, both in
a controlled setting to gauge the importance of non-dissipative post-Newtonian
terms and derive scaling relations for the cross-section of GW captures, as
well as experiments tuned to the strong interactions from state-of-the art
globular cluster models to assess the relative importance of the binary-binary
channel at facilitating GW captures and the resultant eccentricity
distributions of inspiral from channel. Although binary-binary interactions are
10-100 times less frequent in globular clusters than binary-single
interactions, their longer lifetime and more complex dynamics leads to a higher
probability for GW captures to occur during the encounter. We find that
binary-binary interactions contribute 25-45% of the eccentric mergers which
occur during strong black hole encounters in globular clusters, regardless of
the properties of the cluster environment. The inclusion of higher multiplicity
encounters in dense star clusters therefore have major implications on the
predicted rates of highly eccentric binaries potentially detectable by the
LIGO/Virgo network. As gravitational waveforms of eccentric inspirals are
distinct from those generated by merging binaries which have circularized,
measurements of eccentricity in such systems would highly constrain their
formation scenario.
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