TY - JOUR

T1 - Novel Ringdown Amplitude-Phase Consistency Test

AU - Forteza, Xisco Jiménez

AU - Bhagwat, Swetha

AU - Kumar, Sumit

AU - Pani, Paolo

N1 - Funding Information: We acknowledge the Max Planck Gesellschaft for support, and we are grateful to the Atlas cluster computing team at AEI Hannover for their help. The authors are specially thankful to Lionel London, Cecilio García-Quiros, and Juan Calderon-Bustillo for the invaluable discussions and further clarifications about the NR phase alignment and phase conventions. X. Jimenez is also thankful to P. Mourier for the useful discussions about the correspondence of the fit and parameter-estimation results. S. B. is supported by the UKRI Stephen Hawking Fellowship, Grant Ref. EP/W005727. P. P. acknowledges financial support provided under the European Union’s H2020 ERC, Starting Grant agreement no. DarkGRA–757480. We also acknowledge support under the MIUR PRIN (Grant 2020KR4KN2 “String Theory as a bridge between Gauge Theories and Quantum Gravity”) and FARE (GW-NEXT, CUP: B84I20000100001, 2020KR4KN2) programmes, and from the Amaldi Research Center funded by the MIUR program “Dipartimento di Eccellenza” (CUP: B81I18001170001).

PY - 2023/1/13

Y1 - 2023/1/13

N2 - The ringdown signal emitted during a binary black hole coalescence can be modeled as a linear superposition of the characteristic damped modes of the remnant black hole that get excited during the merger phase. While checking the consistency of the measured frequencies and damping times against the Kerr BH spectrum predicted by general relativity (GR) is a cornerstone of strong-field tests of gravity, the consistency of measured excitation amplitudes and phases have been largely left unexplored. For a nonprecessing, quasicircular binary black hole merger, we find that GR predicts a narrow region in the space of mode amplitude ratio and phase difference, independently of the spin of the binary components. Using this unexpected result, we develop a new null test of strong-field gravity which demands that the measured amplitudes and phases of different ringdown modes should lie within this narrow region predicted by GR. We call this the amplitude-phase consistency test and introduce a procedure for performing it using information from the ringdown signal. Lastly, we apply this test to the GW190521 event, using the multimodal ringdown parameters inferred by Capano et al. [arXiv:2105.05238]. While ringdown measurements errors for this event are large, we show that GW190521 is consistent with the amplitude-phase consistency test. Our test is particularly well suited for accommodating multiple loud ringdown detections as those expected in the near future, and can be used complementarily to standard black-hole spectroscopy as a proxy for modified gravity, compact objects other than black holes, binary precession and eccentricity.

AB - The ringdown signal emitted during a binary black hole coalescence can be modeled as a linear superposition of the characteristic damped modes of the remnant black hole that get excited during the merger phase. While checking the consistency of the measured frequencies and damping times against the Kerr BH spectrum predicted by general relativity (GR) is a cornerstone of strong-field tests of gravity, the consistency of measured excitation amplitudes and phases have been largely left unexplored. For a nonprecessing, quasicircular binary black hole merger, we find that GR predicts a narrow region in the space of mode amplitude ratio and phase difference, independently of the spin of the binary components. Using this unexpected result, we develop a new null test of strong-field gravity which demands that the measured amplitudes and phases of different ringdown modes should lie within this narrow region predicted by GR. We call this the amplitude-phase consistency test and introduce a procedure for performing it using information from the ringdown signal. Lastly, we apply this test to the GW190521 event, using the multimodal ringdown parameters inferred by Capano et al. [arXiv:2105.05238]. While ringdown measurements errors for this event are large, we show that GW190521 is consistent with the amplitude-phase consistency test. Our test is particularly well suited for accommodating multiple loud ringdown detections as those expected in the near future, and can be used complementarily to standard black-hole spectroscopy as a proxy for modified gravity, compact objects other than black holes, binary precession and eccentricity.

UR - http://www.scopus.com/inward/record.url?scp=85146347868&partnerID=8YFLogxK

U2 - 10.48550/arXiv.2205.14910

DO - 10.48550/arXiv.2205.14910

M3 - Article

C2 - 36706405

AN - SCOPUS:85146347868

VL - 130

JO - Physical review letters

JF - Physical review letters

SN - 0031-9007

IS - 2

M1 - 021001

ER -