{"article_processing_charge":"Yes","article_type":"original","scopus_import":"1","ddc":["520"],"type":"journal_article","publication":"The Astrophysical Journal Letters","date_updated":"2026-05-04T09:54:18Z","doi":"10.3847/2041-8213/ae2bff","publication_status":"published","file_date_updated":"2026-05-04T09:49:53Z","article_number":"L44","language":[{"iso":"eng"}],"corr_author":"1","abstract":[{"lang":"eng","text":"GW231123 represents the most massive binary–black hole merger detected to date, lying firmly within, or even above, the pair-instability mass gap. The component spins are both exceptionally high (a1 = 0.90 +0.10/-0.19, a2 = 0.80 +0.20/-0.51), which is difficult to explain with repeated mergers. Here we show that the black hole spin vectors are closely aligned with each other while significantly tilted relative to the binary’s orbital angular momentum, pointing to a common accretion-driven origin. We examine astrophysical formation channels capable of producing near-equal, high-mass, and mutually aligned spins consistent with GW231123—particularly binaries embedded in AGN disks and Population III remnants, which grew via coherent misaligned gas accretion. We further argue that other high-mass, high-spin events, e.g., GW190521, may share a similar evolutionary pathway. These findings underscore the critical role of sustained, coherent accretion in shaping the most extreme black hole binaries."}],"oa":1,"day":"10","OA_type":"gold","year":"2026","volume":996,"title":"Accretion is all you need: Black Hole spin alignment in merger GW231123 indicates accretion pathway","month":"01","status":"public","tmp":{"name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode","image":"/images/cc_by.png","short":"CC BY (4.0)"},"department":[{"_id":"ZoHa"}],"date_created":"2026-04-12T22:01:49Z","publisher":"IOP Publishing","citation":{"apa":"Bartos, I., &#38; Haiman, Z. (2026). Accretion is all you need: Black Hole spin alignment in merger GW231123 indicates accretion pathway. <i>The Astrophysical Journal Letters</i>. IOP Publishing. <a href=\"https://doi.org/10.3847/2041-8213/ae2bff\">https://doi.org/10.3847/2041-8213/ae2bff</a>","ieee":"I. Bartos and Z. Haiman, “Accretion is all you need: Black Hole spin alignment in merger GW231123 indicates accretion pathway,” <i>The Astrophysical Journal Letters</i>, vol. 996, no. 2. IOP Publishing, 2026.","ama":"Bartos I, Haiman Z. Accretion is all you need: Black Hole spin alignment in merger GW231123 indicates accretion pathway. <i>The Astrophysical Journal Letters</i>. 2026;996(2). doi:<a href=\"https://doi.org/10.3847/2041-8213/ae2bff\">10.3847/2041-8213/ae2bff</a>","mla":"Bartos, Imre, and Zoltán Haiman. “Accretion Is All You Need: Black Hole Spin Alignment in Merger GW231123 Indicates Accretion Pathway.” <i>The Astrophysical Journal Letters</i>, vol. 996, no. 2, L44, IOP Publishing, 2026, doi:<a href=\"https://doi.org/10.3847/2041-8213/ae2bff\">10.3847/2041-8213/ae2bff</a>.","short":"I. Bartos, Z. Haiman, The Astrophysical Journal Letters 996 (2026).","ista":"Bartos I, Haiman Z. 2026. Accretion is all you need: Black Hole spin alignment in merger GW231123 indicates accretion pathway. The Astrophysical Journal Letters. 996(2), L44.","chicago":"Bartos, Imre, and Zoltán Haiman. “Accretion Is All You Need: Black Hole Spin Alignment in Merger GW231123 Indicates Accretion Pathway.” <i>The Astrophysical Journal Letters</i>. IOP Publishing, 2026. <a href=\"https://doi.org/10.3847/2041-8213/ae2bff\">https://doi.org/10.3847/2041-8213/ae2bff</a>."},"_id":"21713","intvolume":"       996","publication_identifier":{"issn":["2041-8205"],"eissn":["2041-8213"]},"issue":"2","quality_controlled":"1","date_published":"2026-01-10T00:00:00Z","user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","oa_version":"Published Version","OA_place":"publisher","external_id":{"arxiv":["2508.08558"]},"arxiv":1,"DOAJ_listed":"1","author":[{"full_name":"Bartos, Imre","first_name":"Imre","last_name":"Bartos"},{"first_name":"Zoltán","last_name":"Haiman","orcid":"0000-0003-3633-5403","id":"7c006e8c-cc0d-11ee-8322-cb904ef76f36","full_name":"Haiman, Zoltán"}],"file":[{"date_updated":"2026-05-04T09:49:53Z","file_id":"21788","creator":"dernst","content_type":"application/pdf","date_created":"2026-05-04T09:49:53Z","relation":"main_file","access_level":"open_access","file_size":866725,"success":1,"checksum":"ac46ba3d13f0150ccbc42665bed3ae47","file_name":"2026_AstrophysicalJourLetters_Bartos.pdf"}],"acknowledgement":"The authors thank Davide Gerosa and Matthew Mould for valuable suggestions. We are grateful for support by the National Science Foundation under grant No. PHY-2309024 (I.B.) and by NASA under grants 80NSSC22K0822 and 80NSSC24K0440 (Z.H.). We used OpenAI’s ChatGPT (OpenAI 2025) during the preparation of this manuscript. This material is based upon work supported by NSF’s LIGO Laboratory, which is a major facility fully funded by the National Science Foundation.","has_accepted_license":"1"}