Formation of extremely low-mass white dwarf binaries undergoing enhanced angular momentum loss

Fuente: arXiv
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Main Authors: Zhao, Ziqi, Li, Zhenwei, Liu, Zhengwei, Chen, Hailiang, Ge, Hongwei, Meng, Xiangcun, Jiang, Dengkai, Chen, Xuefei, Han, Zhanwen
Format: Preprint
Published: 2026
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author Zhao, Ziqi
Li, Zhenwei
Liu, Zhengwei
Chen, Hailiang
Ge, Hongwei
Meng, Xiangcun
Jiang, Dengkai
Chen, Xuefei
Han, Zhanwen
author_facet Zhao, Ziqi
Li, Zhenwei
Liu, Zhengwei
Chen, Hailiang
Ge, Hongwei
Meng, Xiangcun
Jiang, Dengkai
Chen, Xuefei
Han, Zhanwen
contents Extremely low-mass white dwarfs (ELM WDs) are helium (He) WDs with masses below $\sim 0.3\ M_{\odot}$, mainly formed through binary interaction. ELM WD binaries typically are formed from two channels, namely the stable Roche lobe overflow (RLOF) channel and the common envelope ejection channel. For ELM WD binaries produced from RLOF channel, the ELM WD mass has a strong correlation with the orbital period, i.e., the so-called WD mass-orbital period relation. However, the observations in the ELM Survey show that the orbital periods of ELM WD binaries from the RLOF channel are typically shorter than the theoretically predicted values. Extra angular momentum loss (AML) may be needed to explain such a phenomenon. In this work, we assumed that part of the transferred mass from the donor is lost at the outer Lagrangian point and simulated the formation of ELM WD binaries. Enhanced AML enables more mass to be lost during thermal-timescale mass transfer, thereby affecting nuclear burning in the transfer phase and producing ELM WDs with distinct internal structures. These structural differences alter the (pre-)He WD mass-radius relation at the end of mass transfer, which in turn shifts the WD mass-orbital period relation downward. These adjustments enable our model to successfully reproduce the majority of observed systems from the relevant survey projects.
format Preprint
id arxiv_https___arxiv_org_abs_2605_20660
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Formation of extremely low-mass white dwarf binaries undergoing enhanced angular momentum loss
Zhao, Ziqi
Li, Zhenwei
Liu, Zhengwei
Chen, Hailiang
Ge, Hongwei
Meng, Xiangcun
Jiang, Dengkai
Chen, Xuefei
Han, Zhanwen
Solar and Stellar Astrophysics
Extremely low-mass white dwarfs (ELM WDs) are helium (He) WDs with masses below $\sim 0.3\ M_{\odot}$, mainly formed through binary interaction. ELM WD binaries typically are formed from two channels, namely the stable Roche lobe overflow (RLOF) channel and the common envelope ejection channel. For ELM WD binaries produced from RLOF channel, the ELM WD mass has a strong correlation with the orbital period, i.e., the so-called WD mass-orbital period relation. However, the observations in the ELM Survey show that the orbital periods of ELM WD binaries from the RLOF channel are typically shorter than the theoretically predicted values. Extra angular momentum loss (AML) may be needed to explain such a phenomenon. In this work, we assumed that part of the transferred mass from the donor is lost at the outer Lagrangian point and simulated the formation of ELM WD binaries. Enhanced AML enables more mass to be lost during thermal-timescale mass transfer, thereby affecting nuclear burning in the transfer phase and producing ELM WDs with distinct internal structures. These structural differences alter the (pre-)He WD mass-radius relation at the end of mass transfer, which in turn shifts the WD mass-orbital period relation downward. These adjustments enable our model to successfully reproduce the majority of observed systems from the relevant survey projects.
title Formation of extremely low-mass white dwarf binaries undergoing enhanced angular momentum loss
topic Solar and Stellar Astrophysics
url https://arxiv.org/abs/2605.20660