太阳附近白矮星-褐矮星双星的稀缺性：一项种群合成研究
The scarcity of white dwarf-brown dwarf binaries in the solar neighbourhood: A population synthesis study
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中文总结 AI 辅助
本研究通过扩展MRBIN代码开展种群合成模拟，解释太阳附近白矮星-褐矮星双星的稀缺性，发现其数量与观测一致，还重现了相关系统的多项分布特征。
中文摘要 AI 辅助
白矮星-褐矮星（WD-BD）双星本质上是稀有的系统，为研究双星演化和亚恒星伴星的形成提供了独特机会。尽管观测取得了进展，但太阳附近已知的此类双星数量仍很少。本研究探讨其稀缺性是否可由双星形成与演化过程结合观测选择效应来解释。我们将MRBIN双星种群合成代码扩展至亚恒星领域，纳入褐矮星演化模型与扩展初始质量函数，模拟了太阳100秒差距范围内的恒星种群，并将预测的WD-BD种群与观测样本对比。模拟预测100秒差距内有13±5个WD-BD系统，与观测结果一致；这些系统仅占本地白矮星种群的0.1%，证实了其稀有性。模型重现了白矮星质量、温度及轨道周期的整体分布，不过模拟的褐矮星系统温度系统性高于观测值；采用标准公共包层效率0.3时，密近WD-BD双星的生成量不足，表明可能需要更高效率才能重现观测到的短周期系统。模拟还重现了公共包层后双星与宽距非相互作用系统之间中间轨道周期系统的观测缺失，以及主序星-褐矮星双星中褐矮星荒漠减弱的现象。
英文摘要
White dwarf--brown dwarf (WD--BD) binaries are intrinsically rare systems that provide a unique opportunity to study binary evolution and the formation of substellar companions. Despite recent observational progress, only a small number are known in the solar neighbourhood. We investigate whether their scarcity can be explained by binary formation and evolution together with observational selection effects. We extend the MRBIN binary population synthesis code into the substellar regime by incorporating brown dwarf evolutionary models and an extended initial mass function. We simulate the stellar population within 100 pc of the Sun and compare the predicted WD--BD population with the observed sample. Our simulations predict 13+-5 WD--BD systems within 100 pc, consistent with observations. These systems represent only 0.1% of the local white dwarf population, confirming their rarity. The models reproduce the overall distributions of white dwarf masses, temperatures, and orbital periods, although the simulated brown dwarfs are systematically hotter than observed. Close WD--BD binaries are underproduced with the standard common-envelope efficiency 0.3, suggesting that higher efficiencies may be required to reproduce the observed short-period systems. The simulations also reproduce the observed deficit of systems at intermediate orbital periods between post-common-envelope binaries and wide non-interacting systems, as well as a weakened brown dwarf desert in main-sequence--brown dwarf binaries.
发表机构
- Universitat Politècnica de Catalunya（加泰罗尼亚理工大学）
- Institut d’Estudis Espacials de Catalunya（加泰罗尼亚空间研究所）
- University of Leicester（莱斯特大学）
- Sun Yat-sen University（中山大学）
- CSST Science Center for the Guangdong-HongKong-Macau Great Bay Area, Sun Yat-sen University（中山大学粤港澳大湾区嫦娥科学中心）
- Yunnan Observatories, Chinese Academy of Sciences（中国科学院云南天文台）
- International Centre of Supernovae, Yunnan Key Laboratory（云南省超新星国际研究中心）
- University of Chinese Academy of Sciences（中国科学院大学）
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