Searching for a Ringdown Overtone in GW150914

Abstract

We reanalyze the GW150914 post-merger data searching for quasinormal modes beyond the fundamental, quadrupolar mode. There is currently an ongoing disagreement in the literature about whether, and to what extent, the data contains evidence for a quasinormal mode overtone. We use a frequency-domain approach to ringdown data analysis that was recently proposed by the authors. Our analysis has several advantages compared to other analyses performed mainly in the time domain; in particular, the source sky position and the ringdown start time are marginalized over (as opposed to simply being fixed) as part of a Bayesian ringdown analysis. We find tentative evidence for an overtone in GW150914, but at a lower significance than reported elsewhere. Our preferred analysis, marginalizing over the uncertainty in the time of peak strain amplitude, gives a posterior on the overtone amplitude peaked away from zero at $\sim 1.8\sigma$.

12 pages, 9 figures, plus appendices (accepted in Physical Review D on 19 July 2022)

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• Advanced LIGO
• GW190521: A Binary Black Hole Merger with a Total Mass of $150M_{\odot }$
• Observational Black Hole Spectroscopy: A time-domain multimode analysis of GW150914
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• Calibration Uncertainty for Advanced LIGO's First and Second Observing Runs
• Ringdown overtones, black hole spectroscopy, and no-hair theorem tests
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Cited by in corpus (13)

• Nonlinearities in Black Hole Ringdowns
• Generation and propagation of nonlinear quasi-normal modes of a Schwarzschild black hole
• Quasinormal-mode filters: a new approach to analyze the gravitational-wave ringdown of binary black-hole mergers
• Black-hole ringdown as a probe of higher-curvature gravity theories
• Pseudospectrum and binary black hole merger transients
• Using rational filters to uncover the first ringdown overtone in GW150914
• Black hole spectroscopy by mode cleaning
• Conserved currents for Kerr and orthogonality of quasinormal modes
• Constraining modifications of black hole perturbation potentials near the light ring with quasinormal modes
• A parametrized quasi-normal mode framework for non-Schwarzschild metrics
• Measuring deviations from the Kerr geometry with black hole ringdown
• Slowly Decaying Ringdown of a Rapidly Spinning Black Hole: Probing the No-Hair Theorem by Small Mass-Ratio Mergers with LISA
• Theory-agnostic searches for non-gravitational modes in black hole ringdown