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General Relativity and Quantum Cosmology, gr-qc
Abstract:
In this paper, we investigate the morphology of the events from the GWTC-1
catalog of compact binary coalescences as reconstructed by a generic method
based on coherent excess power: we use an open-source version of the coherent
WaveBurst (cWB) analysis pipeline, which does not rely on the detailed
knowledge of the waveform models. cWB extracts the coherent response of the
detectors' network to a generic gravitational wave, using loose bounds on the
duration and bandwidth of the signal. This pipeline version reproduces the same
results that were reported for cWB in recent publications by the LIGO and Virgo
collaborations. The sky localization and waveform reconstruction performed by
cWB are in a good agreement with the most accurate parameter estimates
currently available, i.e. those produced by methods which exploit the detailed
theoretical knowledge of the expected waveform for compact binary coalescences.
However, in some cases cWB also detects features in excess in well-localized
regions of the time-frequency plane. We have then devised and implemented a
procedure to assess the probability that such deviations are significant. Out
of the eleven events reported in the GWTC-1, there are two cases -- the events
GW151012 and GW151226 -- where cWB detects an excess of coherent energy after
the merger ($\Delta t \simeq 0.2$ s and $\simeq 0.1$ s, respectively) with
p-values that call for further investigations ($0.004$ and $0.03$,
respectively), though they are not sufficient to exclude noise fluctuations. We
discuss the morphological properties and plausible interpretations of these
features. We believe that the methodology described in the paper shall be
useful in future searches and we look forward to its application to the the
events of the ongoing observing run of the LIGO-Virgo Collaboration.
