TY - JOUR

T1 - GW190521

T2 - Search for echoes due to stimulated Hawking radiation from black holes

AU - Abedi, Jahed

AU - Longo Micchi, Luís Felipe

AU - Afshordi, Niayesh

N1 - Funding Information: We thank Cecilia Chirenti, Randy Conklin, Cole Miller, Germano Nardini, Alex B. Nielsen, and Francesco Salemi for useful discussions. J. A. thanks the Max Planck Gesellschaft and the Atlas cluster computing team at AEI Hannover for support and computational help. J. A. was supported by ROMFORSK grant Project. No. 302640. L. F. L. M. thanks the financial support of the São Paulo Research Foundation (FAPESP) Grant No. 2017/24919-4 and of Coordenação de Aperfeiçoamento de Pessoal de Nível Superior—Brasil (Capes)—Finance code 001 through the Capes-PrInt program, and thanks Perimeter Institute for the access to its cluster. N. A. is supported by the University of Waterloo, Natural Sciences and Engineering Research Council of Canada (NSERC) and the Perimeter Institute for Theoretical Physics. Research at Perimeter Institute is supported in part by the Government of Canada through the Department of Innovation, Science and Economic Development Canada and by the Province of Ontario through the Ministry of Colleges and Universities. This research has made use of data, software and/or web tools obtained from the GW Open Science Center, a service of LIGO Laboratory, the LIGO Scientific Collaboration and the Virgo Collaboration. LIGO is funded by the U.S. National Science Foundation. Virgo is funded by the French Centre National de Recherche Scientifique (CNRS), the Italian Instituto Nazionale della Fisica Nucleare (INFN) and the Dutch Nikhef, with contributions by Polish and Hungarian institutes.

PY - 2023/8/22

Y1 - 2023/8/22

N2 - Being arguably the most massive binary black hole merger event observed to date, GW190521 deserves special attention. The exceptionally loud ringdown of this merger makes it an ideal candidate to search for gravitational wave echoes, a proposed smoking gun for the quantum structure of black hole horizons. We perform a multipronged search for echoes via two well-established and independent pipelines; a template-based search for stimulated emission of Hawking radiation, or Boltzmann echoes, and the model-agnostic coherent WaveBurst (cwb) search. Stimulated Hawking radiation from the merger is proposed to lead to postmerger echoes at horizon mode frequency of ∼50 Hz (for quadrupolar gravitational radiation), repeating at intervals of ∼1 second, due to partial reflection off Planckian quantum structure of the horizon. An analysis using dynamic nested sampling yields a Bayesian evidence of 8-2+4 (90% confidence level) for this signal following GW190521, carrying an excess of 6-5+10% in gravitational wave energy, relative to the main event (consistent with the predicted amplitude of Boltzmann echoes). The "look-elsewhere"effect is estimated by using general relativity (plus Boltzmann echoes) injections in real data, before and after the event, giving a false (true) positive detection probability for higher Bayes factors of 1.5-0.9+1.2% (35±7%). Similarly, the reconstructed waveform of the first echo in cwb carries an energy excess of 13-7+16%. While the current evidence for stimulated Hawking radiation does not reach the gold standard of 5σ (or p-value <3×10-7), our findings are in line with predictions for stimulated Hawking radiation at current detector sensitivities. The next generation of gravitational wave observatories can thus draw a definitive conclusion on the quantum nature of black hole horizons.

AB - Being arguably the most massive binary black hole merger event observed to date, GW190521 deserves special attention. The exceptionally loud ringdown of this merger makes it an ideal candidate to search for gravitational wave echoes, a proposed smoking gun for the quantum structure of black hole horizons. We perform a multipronged search for echoes via two well-established and independent pipelines; a template-based search for stimulated emission of Hawking radiation, or Boltzmann echoes, and the model-agnostic coherent WaveBurst (cwb) search. Stimulated Hawking radiation from the merger is proposed to lead to postmerger echoes at horizon mode frequency of ∼50 Hz (for quadrupolar gravitational radiation), repeating at intervals of ∼1 second, due to partial reflection off Planckian quantum structure of the horizon. An analysis using dynamic nested sampling yields a Bayesian evidence of 8-2+4 (90% confidence level) for this signal following GW190521, carrying an excess of 6-5+10% in gravitational wave energy, relative to the main event (consistent with the predicted amplitude of Boltzmann echoes). The "look-elsewhere"effect is estimated by using general relativity (plus Boltzmann echoes) injections in real data, before and after the event, giving a false (true) positive detection probability for higher Bayes factors of 1.5-0.9+1.2% (35±7%). Similarly, the reconstructed waveform of the first echo in cwb carries an energy excess of 13-7+16%. While the current evidence for stimulated Hawking radiation does not reach the gold standard of 5σ (or p-value <3×10-7), our findings are in line with predictions for stimulated Hawking radiation at current detector sensitivities. The next generation of gravitational wave observatories can thus draw a definitive conclusion on the quantum nature of black hole horizons.

UR - http://www.scopus.com/inward/record.url?scp=85172779018&partnerID=8YFLogxK

U2 - 10.48550/arXiv.2201.00047

DO - 10.48550/arXiv.2201.00047

M3 - Article

AN - SCOPUS:85172779018

VL - 108

JO - Physical Review D

JF - Physical Review D

SN - 2470-0010

IS - 4

M1 - 044047

ER -