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General Relativity and Quantum Cosmology, gr-qc
Abstract:
The laser-interferometer space antenna (LISA) will be launched in the mid
2030s. It promises to observe the coalescence of massive black-hole (BH)
binaries with signal-to-noise ratios (SNRs) reaching thousands. Crucially, it
will detect some of these binaries with high SNR both in the inspiral and the
merger-ringdown stages. Such signals are ideal for tests of General Relativity
(GR) using information from the whole waveform. Here, we consider
astrophysically motivated binary systems at the high-mass end of the population
observable by LISA, and simulate their LISA signals using the newly developed
parametrised, multipolar, aligned-spin effective-one-body model: pSEOBNRv5HM.
The merger-ringdown signal in this model depends on the binary properties
(masses and spins), and also on parameters that describe fractional deviations
from the GR quasi-normal-mode frequencies of the remnant BH. Performing full
Bayesian analyses, we assess to which accuracy LISA will be able to constrain
deviations from GR in the ringdown signal when using information from the whole
signal. We find that these deviations can typically be constrained to within
$10\%$ and in the best cases to within $1\%$. We also show that we can measure
the binary masses and spins with great accuracy even for very massive BH
systems with low SNR in the inspiral: individual source-frame masses can
typically be constrained to within $10\%$ and as precisely as $1\%$, and
individual spins can typically be constrained to within $0.1$ and as precisely
as $0.001$. Finally, we probe the accuracy of the SEOBNRv5HM waveform family by
performing synthetic injections of GR numerical-relativity waveforms. For the
source parameters considered, we measure erroneous deviations from GR due to
systematics in the waveform model. These results confirm the need for improving
waveform models to perform tests of GR with binary BHs at high SNR with LISA.
