Puzzling two-stage size evolution of an ultraluminous gamma-ray burst jet

Puzzling two-stage size evolution of an ultraluminous gamma-ray burst jet | 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 Puzzling two-stage size evolution of an ultraluminous gamma-ray burst jet Tao An, Jin-Jun Geng, Yingkang Zhang, Hao-Xuan Gao, Fan Xu, Tianrui Sun, and 15 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4123241/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted You are reading this latest preprint version Abstract Gamma-ray bursts (GRBs) are the most luminous stellar explosions in the Universe, in which relativistic jets are involved. GRB 221009A stands out as the brightest GRB ever observed, providing a unique opportunity to probe the properties of an ultrarelativistic jet. Here, we report our very long baseline interferometry (VLBI) observation on the extremely bright GRB 221009A from 5 to 26 days after the burst. An intriguing two-stage evolution of the source size of this GRB is revealed by combining this data with later VLBI data. The observed size initially increases slowly as ~ t obs 0.15 during the first month, but expands with a much faster rate as ~ t obs 2.21 at later times. This unprecedented two-stage size evolution cannot be explained by the existing theoretical models invoking a non-spreading top-hat jet or a conventional structured jet and thus challenges our current understanding of this GRB jet. The transition may suggest the beginning of rapid sideways expansion of a narrow jet as the relativistic jet decelerates enough or the emergence of a new emission component. Our findings unveil the complex jet dynamics of GRB 221009A, highlighting the necessity of direct measurements of the size and geometry of the emission region in studying low-redshift GRBs in the multi-wavelength era. Physical sciences/Astronomy and planetary science/Astronomy and astrophysics/High-energy astrophysics Physical sciences/Astronomy and planetary science/Astronomy and astrophysics/Transient astrophysical phenomena Full Text Additional Declarations There is NO Competing Interest. Cite Share Download PDF Status: Under Review 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-4123241","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Physical Sciences - Article","associatedPublications":[],"authors":[{"id":282343631,"identity":"f26b8582-e0ff-493a-9771-b20535fe1caa","order_by":0,"name":"Tao An","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAuElEQVRIiWNgGAWjYNCCCoYEUpQzA/EZkrUwtpGihX92/8EPH+fV5fG3NzB++MFgl0dQi8Sdw8ySM7cdLpY4c4BZsochuZiwNTeSGaR5tx1IbLiRwCDNwABkENIhfyOZ+TfvnLrE+TcSmH8TpcXgRjKbNG8Dc+KGGwlsxNlieCPZzHLGscOJG88cbLPsMUgmrEXuRuLjGx9q6hLnHW8+fONHhR1hLUiAEajYgAT1o2AUjIJRMApwAwCIBT4hJ3LaXAAAAABJRU5ErkJggg==","orcid":"https://orcid.org/0000-0003-4341-0029","institution":"Shanghai Astronomical Observatory","correspondingAuthor":true,"prefix":"","firstName":"Tao","middleName":"","lastName":"An","suffix":""},{"id":282343632,"identity":"a9a2bbee-c7fe-44ac-b22f-c6f34961a3be","order_by":1,"name":"Jin-Jun Geng","email":"","orcid":"https://orcid.org/0000-0001-9648-7295","institution":"Purple Mountain Observatory","correspondingAuthor":false,"prefix":"","firstName":"Jin-Jun","middleName":"","lastName":"Geng","suffix":""},{"id":282343633,"identity":"f2cad466-ecfd-4b64-9db3-e5209c751734","order_by":2,"name":"Yingkang Zhang","email":"","orcid":"https://orcid.org/0000-0001-8256-8887","institution":"Shanghai Astronomical Observatory, Key Laboratory of Radio Astronomy, Chinese Academy of Sciences","correspondingAuthor":false,"prefix":"","firstName":"Yingkang","middleName":"","lastName":"Zhang","suffix":""},{"id":282343634,"identity":"ca42631e-58d4-4c6e-9d5f-cb08003d043b","order_by":3,"name":"Hao-Xuan Gao","email":"","orcid":"","institution":"Purple Mountain Observatory","correspondingAuthor":false,"prefix":"","firstName":"Hao-Xuan","middleName":"","lastName":"Gao","suffix":""},{"id":282343635,"identity":"ead63a89-306f-40da-a489-3c0ffb0f098c","order_by":4,"name":"Fan Xu","email":"","orcid":"","institution":"Nanjing University","correspondingAuthor":false,"prefix":"","firstName":"Fan","middleName":"","lastName":"Xu","suffix":""},{"id":282343636,"identity":"a69e6e33-cfd4-4c65-91cd-4819139ca050","order_by":5,"name":"Tianrui Sun","email":"","orcid":"","institution":"Purple Mountain Observatory, Chinese Academy of Sciences","correspondingAuthor":false,"prefix":"","firstName":"Tianrui","middleName":"","lastName":"Sun","suffix":""},{"id":282343637,"identity":"b33185a5-047f-4bd1-9e67-a3feba563ee0","order_by":6,"name":"Bing Li","email":"","orcid":"https://orcid.org/0000-0002-0238-834X","institution":"Institute of High Energy Physics, Chinese Academy of Sciences, 19B Yuquan Road, Beijing 100049,People's Republic of China","correspondingAuthor":false,"prefix":"","firstName":"Bing","middleName":"","lastName":"Li","suffix":""},{"id":282343638,"identity":"12a38a73-6319-4db0-9f77-5a5d103061cf","order_by":7,"name":"Ailing Wang","email":"","orcid":"https://orcid.org/0000-0002-7351-5801","institution":"Shanghai Astronomical Observatory","correspondingAuthor":false,"prefix":"","firstName":"Ailing","middleName":"","lastName":"Wang","suffix":""},{"id":282343639,"identity":"d8fd2afb-4e70-4c55-acdb-5466c667bb90","order_by":8,"name":"Zhi-Jun Xu","email":"","orcid":"https://orcid.org/0000-0003-4853-7619","institution":"Shanghai Astronomical Observatory","correspondingAuthor":false,"prefix":"","firstName":"Zhi-Jun","middleName":"","lastName":"Xu","suffix":""},{"id":282343640,"identity":"aca517d1-e210-4755-95f7-6404c3e81bb1","order_by":9,"name":"Yuan-Qi Liu","email":"","orcid":"","institution":"Shanghai Astronomical Observatory","correspondingAuthor":false,"prefix":"","firstName":"Yuan-Qi","middleName":"","lastName":"Liu","suffix":""},{"id":282343641,"identity":"ae17ed80-8526-4f25-a06e-dfbaa0d2e763","order_by":10,"name":"Jun Yang","email":"","orcid":"https://orcid.org/0000-0002-2322-5232","institution":"Chalmers University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Jun","middleName":"","lastName":"Yang","suffix":""},{"id":282343642,"identity":"f86f0301-b178-42e2-a94f-51c64bbe5304","order_by":11,"name":"Chen-Ran Hu","email":"","orcid":"","institution":"Nanjing University","correspondingAuthor":false,"prefix":"","firstName":"Chen-Ran","middleName":"","lastName":"Hu","suffix":""},{"id":282343643,"identity":"efd1beb5-5680-45ad-a982-f21901a651be","order_by":12,"name":"Li Liang","email":"","orcid":"","institution":"ICRANet","correspondingAuthor":false,"prefix":"","firstName":"Li","middleName":"","lastName":"Liang","suffix":""},{"id":282343644,"identity":"223d03c8-294f-4aab-a9be-7c881f98b926","order_by":13,"name":"Yu Wang","email":"","orcid":"","institution":"ICRANet","correspondingAuthor":false,"prefix":"","firstName":"Yu","middleName":"","lastName":"Wang","suffix":""},{"id":282343645,"identity":"fb122ea8-3c20-4236-85fe-e738fd29f46d","order_by":14,"name":"Ye Li","email":"","orcid":"","institution":"Peking University","correspondingAuthor":false,"prefix":"","firstName":"Ye","middleName":"","lastName":"Li","suffix":""},{"id":282343646,"identity":"cb88410d-72ac-44cc-a638-fa8074fe1e52","order_by":15,"name":"Di Xiao","email":"","orcid":"","institution":"Purple Mountain Observatory","correspondingAuthor":false,"prefix":"","firstName":"Di","middleName":"","lastName":"Xiao","suffix":""},{"id":282343647,"identity":"9de17ea2-e506-4dcd-b6d2-7a0dc4fe92bd","order_by":16,"name":"Jia Ren","email":"","orcid":"","institution":"Nanjing University","correspondingAuthor":false,"prefix":"","firstName":"Jia","middleName":"","lastName":"Ren","suffix":""},{"id":282343648,"identity":"dba6dd8a-34a5-4cb4-a829-15191cdd7e9d","order_by":17,"name":"Xue-Feng Wu","email":"","orcid":"https://orcid.org/0000-0002-6299-1263","institution":"Purple Mountain Observatory, Chinese Academy of Sciences","correspondingAuthor":false,"prefix":"","firstName":"Xue-Feng","middleName":"","lastName":"Wu","suffix":""},{"id":282343649,"identity":"7bb033ed-fd76-4c11-9cad-1dd3c9ac6f1d","order_by":18,"name":"Yong-Feng Huang","email":"","orcid":"","institution":"Nanjing University","correspondingAuthor":false,"prefix":"","firstName":"Yong-Feng","middleName":"","lastName":"Huang","suffix":""},{"id":282343650,"identity":"c8a54a39-5349-455d-a6ce-fe66ac70041f","order_by":19,"name":"Z. G. Dai","email":"","orcid":"","institution":"University of Science and Technology of China","correspondingAuthor":false,"prefix":"","firstName":"Z.","middleName":"G.","lastName":"Dai","suffix":""},{"id":282343651,"identity":"faae4e5a-ba59-491d-a6cb-78dfbf3aafc6","order_by":20,"name":"Bing Zhang","email":"","orcid":"","institution":"Nevada Center for Astrophysics, University of Nevada","correspondingAuthor":false,"prefix":"","firstName":"Bing","middleName":"","lastName":"Zhang","suffix":""}],"badges":[],"createdAt":"2024-03-18 12:30:22","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4123241/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4123241/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":55128614,"identity":"e09ec799-8d25-4b27-92c3-55ad5ef97f8b","added_by":"auto","created_at":"2024-04-23 03:41:19","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":843692,"visible":true,"origin":"","legend":"Article File","description":"","filename":"Main.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4123241/v1_covered_316a7619-50d8-41f2-87c1-7d866f5eea42.pdf"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Puzzling two-stage size evolution of an ultraluminous gamma-ray burst jet","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":false,"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":"nature-portfolio","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"","title":"Nature Portfolio","twitterHandle":"","acdcEnabled":false,"dfaEnabled":false,"editorialSystem":"ejp","reportingPortfolio":"","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-4123241/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4123241/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"Gamma-ray bursts (GRBs) are the most luminous stellar explosions in the Universe, in which relativistic jets are involved. GRB 221009A stands out as the brightest GRB ever observed, providing a unique opportunity to probe the properties of an ultrarelativistic jet. Here, we report our very long baseline interferometry (VLBI) observation on the extremely bright GRB 221009A from 5 to 26 days after the burst. An intriguing two-stage evolution of the source size of this GRB is revealed by combining this data with later VLBI data. The observed size initially increases slowly as ~ t\u003csub\u003eobs\u003c/sub\u003e\u003csup\u003e0.15\u003c/sup\u003e during the first month, but expands with a much faster rate as ~ t\u003csub\u003eobs\u003c/sub\u003e\u003csup\u003e2.21\u003c/sup\u003e at later times. This unprecedented two-stage size evolution cannot be explained by the existing theoretical models invoking a non-spreading top-hat jet or a conventional structured jet and thus challenges our current understanding of this GRB jet. The transition may suggest the beginning of rapid sideways expansion of a narrow jet as the relativistic jet decelerates enough or the emergence of a new emission component. Our findings unveil the complex jet dynamics of GRB 221009A, highlighting the necessity of direct measurements of the size and geometry of the emission region in studying low-redshift GRBs in the multi-wavelength era.","manuscriptTitle":"Puzzling two-stage size evolution of an ultraluminous gamma-ray burst jet","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-04-23 03:33:10","doi":"10.21203/rs.3.rs-4123241/v1","editorialEvents":[],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"nature-astronomy","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"natastron","sideBox":"Learn more about [Nature Astronomy](http://www.nature.com/natastron/)","snPcode":"","submissionUrl":"","title":"Nature Astronomy","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Nature Research","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"8c85dd24-5324-4e7b-9612-7e83dc753eec","owner":[],"postedDate":"April 23rd, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":29730205,"name":"Physical sciences/Astronomy and planetary science/Astronomy and astrophysics/High-energy astrophysics"},{"id":29730206,"name":"Physical sciences/Astronomy and planetary science/Astronomy and astrophysics/Transient astrophysical phenomena"}],"tags":[],"updatedAt":"2024-04-23T03:33:10+00:00","versionOfRecord":[],"versionCreatedAt":"2024-04-23 03:33:10","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4123241","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4123241","identity":"rs-4123241","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}