High-precision source characterization of intermediate mass-ratio black hole coalescences with gravitational waves: The importance of higher-order multipoles. (arXiv:2105.04422v2 [gr-qc] UPDATED)
<a href="http://arxiv.org/find/gr-qc/1/au:+Islam_T/0/1/0/all/0/1">Tousif Islam</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Field_S/0/1/0/all/0/1">Scott E. Field</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Haster_C/0/1/0/all/0/1">Carl-Johan Haster</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Smith_R/0/1/0/all/0/1">Rory Smith</a>
Intermediate mass ratio inspiral (IMRI) binaries — containing stellar-mass
black holes coalescing into intermediate-mass black holes ($M>100M_{odot}$) —
are a highly anticipated source of gravitational waves (GWs) for Advanced
LIGO/Virgo. Their detection and source characterization would provide a unique
probe of strong-field gravity and stellar evolution. Due to the asymmetric
component masses and the large primary, these systems generically excite
subdominant modes while reducing the importance of the dominant quadrupole
mode. Including higher order harmonics can also result in a $10%-25%$
increase in signal-to-noise ratio for IMRIs, which may help to detect these
systems. We show that by including subdominant GW modes into the analysis we
can achieve a precise characterization of IMRI source properties. For example,
we find that the source properties for IMRIs can be measured to within
$2%-15%$ accuracy at a fiducial signal-to-noise ratio of 25 if subdominant
modes are included. When subdominant modes are neglected, the accuracy degrades
to $9%-44%$ and significant biases are seen in chirp mass, mass ratio,
primary spin and luminosity distances. We further demonstrate that including
subdominant modes in the waveform model can enable an informative measurement
of both individual spin components and improve the source localization by a
factor of $sim$10. We discuss some important astrophysical implications of
high-precision source characterization enabled by subdominant modes such as
constraining the mass gap and probing formation channels.
Intermediate mass ratio inspiral (IMRI) binaries — containing stellar-mass
black holes coalescing into intermediate-mass black holes ($M>100M_{odot}$) —
are a highly anticipated source of gravitational waves (GWs) for Advanced
LIGO/Virgo. Their detection and source characterization would provide a unique
probe of strong-field gravity and stellar evolution. Due to the asymmetric
component masses and the large primary, these systems generically excite
subdominant modes while reducing the importance of the dominant quadrupole
mode. Including higher order harmonics can also result in a $10%-25%$
increase in signal-to-noise ratio for IMRIs, which may help to detect these
systems. We show that by including subdominant GW modes into the analysis we
can achieve a precise characterization of IMRI source properties. For example,
we find that the source properties for IMRIs can be measured to within
$2%-15%$ accuracy at a fiducial signal-to-noise ratio of 25 if subdominant
modes are included. When subdominant modes are neglected, the accuracy degrades
to $9%-44%$ and significant biases are seen in chirp mass, mass ratio,
primary spin and luminosity distances. We further demonstrate that including
subdominant modes in the waveform model can enable an informative measurement
of both individual spin components and improve the source localization by a
factor of $sim$10. We discuss some important astrophysical implications of
high-precision source characterization enabled by subdominant modes such as
constraining the mass gap and probing formation channels.
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