High Eccentricities and High Masses Characterize Gravitational-wave Captures in Galactic Nuclei as Seen by Earth-based Detectors. (arXiv:2011.02507v2 [astro-ph.HE] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Gondan_L/0/1/0/all/0/1">László Gondán</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kocsis_B/0/1/0/all/0/1">Bence Kocsis</a>
The emission of gravitational waves (GWs) during single-single close
encounters in galactic nuclei (GNs) leads to the formation and rapid merger of
highly eccentric stellar-mass black hole (BH) binaries. The distinct
distribution of physical parameters makes it possible to statistically
distinguish this source population from others. Previous studies determined the
expected binary parameter distribution for this source population in single
GNs. Here we take into account the effects of dynamical friction,
post-Newtonian corrections, and observational bias to determine the detected
sources’ parameter-distributions from all GNs in the Universe. We find that the
total binary mass distribution of detected mergers is strongly tilted towards
higher masses. The distribution of initial peak GW frequency is remarkably high
between 1-30Hz, ~26-50% of GW capture sources form above 10Hz with e >~ 0.95.
The eccentricity when first entering the LIGO/Virgo/KAGRA band satisfies
e_{10Hz} > 0.1 for over 92% of sources and e_{10Hz} > 0.8 for ~50-85% of
sources, depending on the level of mass-segregation and the underlying BH mass
function. At the point when the pericenter reaches 10GM/c^2 the eccentricity
satisfies e_{10M} > 0.1 for ~75-98% of the sources, making single-single GW
capture events in GNs the most eccentric source population among the currently
known stellar-mass BH merger channels in the Universe. We identify correlations
between total mass, mass ratio, source detection distance, and eccentricities
e_{10Hz} and e_{10M}. The recently measured source parameters of GW190521 lie
at the peak of the theoretical distributions, making this source a candidate
for this astrophysical merger channel.
The emission of gravitational waves (GWs) during single-single close
encounters in galactic nuclei (GNs) leads to the formation and rapid merger of
highly eccentric stellar-mass black hole (BH) binaries. The distinct
distribution of physical parameters makes it possible to statistically
distinguish this source population from others. Previous studies determined the
expected binary parameter distribution for this source population in single
GNs. Here we take into account the effects of dynamical friction,
post-Newtonian corrections, and observational bias to determine the detected
sources’ parameter-distributions from all GNs in the Universe. We find that the
total binary mass distribution of detected mergers is strongly tilted towards
higher masses. The distribution of initial peak GW frequency is remarkably high
between 1-30Hz, ~26-50% of GW capture sources form above 10Hz with e >~ 0.95.
The eccentricity when first entering the LIGO/Virgo/KAGRA band satisfies
e_{10Hz} > 0.1 for over 92% of sources and e_{10Hz} > 0.8 for ~50-85% of
sources, depending on the level of mass-segregation and the underlying BH mass
function. At the point when the pericenter reaches 10GM/c^2 the eccentricity
satisfies e_{10M} > 0.1 for ~75-98% of the sources, making single-single GW
capture events in GNs the most eccentric source population among the currently
known stellar-mass BH merger channels in the Universe. We identify correlations
between total mass, mass ratio, source detection distance, and eccentricities
e_{10Hz} and e_{10M}. The recently measured source parameters of GW190521 lie
at the peak of the theoretical distributions, making this source a candidate
for this astrophysical merger channel.
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