Detection of a Higher Harmonic Quasi-normal Mode in the Ringdown Signal of GW231123

Detection of a Higher Harmonic Quasi-normal Mode in the Ringdown Signal of GW231123 | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Physical Sciences - Article Detection of a Higher Harmonic Quasi-normal Mode in the Ringdown Signal of GW231123 Yi-Zhong Fan, Hai-Tian Wang, Shao-Peng Tang, Peng-Cheng Li This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7546124/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract The detection of multiple quasinormal modes, as expected in the ringdown phase of a black hole merger, will provide a direct test of general relativity in the strong-field regime and a way to characterize the remnant black hole. In this study, we present the first robust, multi-mode detection from the notable event GW231123. We identify the (2, 0, 0) quasinormal mode with very high statistical confidence (i.e., log 10 (Bayes factor) ~5.3 ), initiating the analysis at 12 M after the merger-a time that lies within the theoretically expected linear regime of the signal. Notably, this axisymmetric mode emerges as the dominant component, exhibiting substantially greater power than the canonical (2, 2, 0) mode. This observation indicates an unusual merger scenario, potentially resulting from a nearly head-on collision between two massive black holes. Moreover, the inferred remnant properties are consistent with the predictions of the no-hair theorem in general relativity. Physical sciences/Astronomy and planetary science/Astronomy and astrophysics/General relativity and gravity Physical sciences/Astronomy and planetary science/Astronomy and astrophysics/High-energy astrophysics Full Text Additional Declarations There is NO Competing Interest. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7546124","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Physical Sciences - Article","associatedPublications":[],"authors":[{"id":514157283,"identity":"1975e338-62ea-4845-8823-97d74e760396","order_by":0,"name":"Yi-Zhong Fan","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAtklEQVRIiWNgGAWjYFACxgcMDBWkaWE2YGA4Q7IWxjZSNBicP8z4uXDenWh+BuaHHxhq7hCh5cBhZumZ257lzmxgM5ZgOPaMCC0H+w9I8247nLvhAIMZA2PDYSK0HGZm/s07B6SF/RuRWo4xs0nzNoC08BBpi+QZZjZrnmNAvzTzFEskHCNCC9/5w8y3eWru5Pazt2/88KGGCC0KB8AUkGQGUgmENTAwyDfAtIyCUTAKRsEowAUAfeA63sSwsDQAAAAASUVORK5CYII=","orcid":"https://orcid.org/0000-0002-8966-6911","institution":"Purple Mountain Observatory","correspondingAuthor":true,"prefix":"","firstName":"Yi-Zhong","middleName":"","lastName":"Fan","suffix":""},{"id":514157284,"identity":"81772d60-055e-4830-a71a-378c194f145b","order_by":1,"name":"Hai-Tian Wang","email":"","orcid":"","institution":"School of Physics, Dalian University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Hai-Tian","middleName":"","lastName":"Wang","suffix":""},{"id":514157285,"identity":"12d06923-5ddc-46f3-83a3-5b4af6fcb450","order_by":2,"name":"Shao-Peng Tang","email":"","orcid":"","institution":"Purple Mountain Observatory","correspondingAuthor":false,"prefix":"","firstName":"Shao-Peng","middleName":"","lastName":"Tang","suffix":""},{"id":514157286,"identity":"d1430452-a625-4159-861a-8ff53b109e4c","order_by":3,"name":"Peng-Cheng Li","email":"","orcid":"","institution":"School of Physics and Optoelectronics, South China University of Technology,","correspondingAuthor":false,"prefix":"","firstName":"Peng-Cheng","middleName":"","lastName":"Li","suffix":""}],"badges":[],"createdAt":"2025-09-05 16:55:27","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7546124/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7546124/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":92936118,"identity":"fc160034-e7a9-4b0e-bee6-fa1921328078","added_by":"auto","created_at":"2025-10-07 10:18:33","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":991305,"visible":true,"origin":"","legend":"Article File","description":"","filename":"fs231123.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7546124/v1_covered_a9c3cba4-477e-4997-a473-c9b7394da9f1.pdf"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Detection of a Higher Harmonic Quasi-normal Mode in the Ringdown Signal of GW231123","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-7546124/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7546124/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe detection of multiple quasinormal modes, as expected in the ringdown phase of a black hole merger, will provide a direct test of general relativity in the strong-field regime and a way to characterize the remnant black hole. In this study, we present the first robust, multi-mode detection from the notable event GW231123. We identify the \u003cstrong\u003e(2, 0, 0)\u003c/strong\u003e quasinormal mode with very high statistical confidence (i.e., \u003cstrong\u003elog\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e10 \u003c/strong\u003e\u003c/sub\u003e(Bayes factor) \u003cstrong\u003e~5.3\u003c/strong\u003e), initiating the analysis at \u003cstrong\u003e12\u003c/strong\u003e\u003cem\u003e\u003cstrong\u003eM\u003c/strong\u003e\u003c/em\u003e after the merger-a time that lies within the theoretically expected linear regime of the signal. Notably, this axisymmetric mode emerges as the dominant component, exhibiting substantially greater power than the canonical \u003cstrong\u003e(2, 2, 0)\u003c/strong\u003e mode. This observation indicates an unusual merger scenario, potentially resulting from a nearly head-on collision between two massive black holes. 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