BEGIN:VCALENDAR VERSION:2.0 PRODID:Data::ICal 0.22 BEGIN:VEVENT DESCRIPTION:Roberto Cotesta\, John Hopkins University\n\n
The gravitation al-wave signal emitted by the black-hole remnant resulting from a binary m erger such as GW190514 consists in a superposition of damped sinu- soids k nown as quasinormal modes. Besides the &ldquo\;fundamental"\; mode (th e one with the longest damping time)\, it is important to detect the so-ca lled &ldquo\;over- tones"\; (modes with shorter damping time)\, becaus e a measurement of their frequencies could allow us to identify the remnan t as a Kerr black hole. We discuss theoretical and observational issues in the analysis of ringdown over- tones. We present theoretical arguments sh owing that the spacetime is not well described as a linearly perturbed bla ck hole close to the peak of the waveform amplitude. Then we analyze GW150 914 post-merger data to understand if recent ringdown overtone detection c laims are robust. We find no evidence in favor of an overtone in the data after the waveform peak. Around the peak\, the log-Bayes factor does not i ndicate the presence of an overtone\, while the support for a non-zero amp litude is sensitive to changes in the starting time much smaller than the overtone damping time. This suggests that claims of an overtone detection are noise-dominated. We perform GW150914-like injections in neighboring se gments of the real detector noise\, and we show that noise can indeed indu ce artificial evidence for an overtone.
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\n DTSTART:20221121T183000Z LOCATION:Physics\, Room 313 SUMMARY:Ringdown overtones in black hole binary mergers END:VEVENT END:VCALENDAR