A Unified Solution to the Low-Mass X-ray Binary Diversity Puzzle: Saturated Magnetic Braking Coupled with Irradiation-Driven Winds
Abstract
The standard magnetic braking (MB) model has long failed to explain key properties of low-mass X-ray binaries (LMXBs)---including their accretion rates, the formation of ultracompact binaries, and orbital expansion---casting doubt on binary evolution and gravitational-wave progenitor predictions. Phenomenological modifications exist, but a unified, physically grounded mechanism has been missing. Here we show that the overlooked coupling between magnetic saturation and irradiation-driven winds (IDW) provides this missing framework. Accretion-powered irradiation enhances the donor wind, which in turn amplifies MB exactly where needed. Our Saturated MB + IDW (SMB+IDW) model simultaneously resolves three outstanding discrepancies with no fine-tuning: (1) it reproduces the full observed distribution of accretion rates across persistent and transient LMXBs; (2) it naturally explains ultracompact X-ray binary formation; and (3) it quantitatively matches the orbital period distribution of descendant millisecond pulsar (MSP) binaries---a critical independent test failed by all previous models. Critically, the SMB+IDW model transforms MB from an externally imposed condition into a self-consistently regulated process tied to the accretion history. By unifying LMXB evolution to MSPs in a single physical picture, our work resolves the long-standing diversity puzzle and establishes a physics-based foundation for next-generation population synthesis, gravitational-wave progenitor predictions, and compact binary interpretation across cosmic time.
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BibTeX
@misc{deng2026unified,
title = {{A Unified Solution to the Low-Mass X-ray Binary Diversity Puzzle: Saturated Magnetic Braking Coupled with Irradiation-Driven Winds}},
author = {Zhu-Ling Deng and Xiang-Dong Li and Bo Wang and Philipp Podsiadlowski and Yong Shao and Dong-Dong Liu and Zhan-Wen Han},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.22816},
eprint = {2610.22816},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.22816},
}
RIS
TY - UNPB
TI - A Unified Solution to the Low-Mass X-ray Binary Diversity Puzzle: Saturated Magnetic Braking Coupled with Irradiation-Driven Winds
AU - Zhu-Ling Deng
AU - Xiang-Dong Li
AU - Bo Wang
AU - Philipp Podsiadlowski
AU - Yong Shao
AU - Dong-Dong Liu
AU - Zhan-Wen Han
PY - 2026
DA - 2026/10/16
PB - arXiv
DO - 10.48550/arxiv.2610.22816
UR - https://arxiv.org/abs/2610.22816
AB - The standard magnetic braking (MB) model has long failed to explain key properties of low-mass X-ray binaries (LMXBs)---including their accretion rates, the formation of ultracompact binaries, and orbital expansion---casting doubt on binary evolution and gravitational-wave progenitor predictions. Phenomenological modifications exist, but a unified, physically grounded mechanism has been missing. Here we show that the overlooked coupling between magnetic saturation and irradiation-driven winds (IDW) provides this missing framework. Accretion-powered irradiation enhances the donor wind, which in turn amplifies MB exactly where needed. Our Saturated MB + IDW (SMB+IDW) model simultaneously resolves three outstanding discrepancies with no fine-tuning: (1) it reproduces the full observed distribution of accretion rates across persistent and transient LMXBs; (2) it naturally explains ultracompact X-ray binary formation; and (3) it quantitatively matches the orbital period distribution of descendant millisecond pulsar (MSP) binaries---a critical independent test failed by all previous models. Critically, the SMB+IDW model transforms MB from an externally imposed condition into a self-consistently regulated process tied to the accretion history. By unifying LMXB evolution to MSPs in a single physical picture, our work resolves the long-standing diversity puzzle and establishes a physics-based foundation for next-generation population synthesis, gravitational-wave progenitor predictions, and compact binary interpretation across cosmic time.
ER -