Accretion is All You Need: Black Hole Spin Alignment in Merger GW231123 Indicates Accretion Pathway

Fuente: arXiv
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Main Authors: Bartos, Imre, Haiman, Zoltan
Format: Preprint
Published: 2025
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author Bartos, Imre
Haiman, Zoltan
author_facet Bartos, Imre
Haiman, Zoltan
contents 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 ($a_1 = 0.90^{+0.10}_{-0.19}$, $a_2 = 0.80^{+0.20}_{-0.51}$), 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 Pop~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.
format Preprint
id arxiv_https___arxiv_org_abs_2508_08558
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Accretion is All You Need: Black Hole Spin Alignment in Merger GW231123 Indicates Accretion Pathway
Bartos, Imre
Haiman, Zoltan
High Energy Astrophysical Phenomena
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 ($a_1 = 0.90^{+0.10}_{-0.19}$, $a_2 = 0.80^{+0.20}_{-0.51}$), 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 Pop~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.
title Accretion is All You Need: Black Hole Spin Alignment in Merger GW231123 Indicates Accretion Pathway
topic High Energy Astrophysical Phenomena
url https://arxiv.org/abs/2508.08558