发表机构
University of British Columbia; Institute of Science and Technology Austria; University of Warwick（不列颠哥伦比亚大学; 奥地利科学技术研究所; 华威大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究汇编迄今最大疏散星团非典型白矮星样本，发现0.8-1.0M☉非DA型白矮星及大质量磁白矮星存在缺失，推测银河系场存在额外大质量并合遗迹群体，星团磁白矮星的磁场出现与质量相关。
AI 中文摘要
疏散星团是研究白矮星（WDs）形成与演化的强大实验室，因其精确约束的年龄可将白矮星与其前身星关联，这对非典型白矮星尤为重要，这类白矮星包括磁白矮星及非氢主导光谱的白矮星，其在银河系场中的起源难以厘清。本研究汇编了迄今最大的疏散星团中非典型白矮星样本：8颗氦主导光谱的非磁白矮星、5颗无特征光谱的白矮星，以及5颗显示氢或氦线的磁白矮星。研究发现，氢大气与氦大气白矮星的初始-最终质量关系无显著差异，空间或运动学也无可靠差异；与银河系场最显著的差异是0.8至1.0倍太阳质量（M☉）间非DA型白矮星的缺失，场中预测有6.0⁺⁰.⁸₋₀.₇颗此类白矮星，但本研究未观测到，概率仅0.37%。大质量磁白矮星也存在类似缺失：20颗质量M_WD≥1.0M☉且有效温度T_eff≥20000K的星团白矮星中仅1颗为磁白矮星，而场中16颗中有10颗。这些缺失与银河系场中存在额外的大质量并合遗迹群体一致，尤其是大质量磁白矮星和温/热DQs型白矮星；这类天体在星团中代表性不足，因年轻星团为某些延迟并合类别提供的时间有限，而年老星团会损失成员或瓦解，银河系场则在银河时标内积累双星演化产物。与单星演化一致的星团磁白矮星进一步表明，磁场出现与质量相关，部分大质量白矮星的磁场出现较早，而年轻低质量白矮星仍符合延迟出现的特征。
英文摘要
Open clusters are powerful laboratories for investigating the formation and evolution of white dwarfs (WDs), as their well-constrained ages link WDs to their progenitor stars. This is particularly valuable for atypical WDs, including magnetic WDs and those with non-hydrogen-dominated spectra, whose origins can be difficult to disentangle in the field. We assemble the largest sample to date of atypical WDs in open clusters: eight non-magnetic WDs with helium-dominated spectra, five with featureless spectra, and five magnetic WDs showing hydrogen or helium lines. We find no significant difference between the initial--final mass relations of hydrogen- and helium-atmosphere WDs, nor robust spatial or kinematic differences. The strongest difference from the field is a deficit of non-DAs between $0.8$ and $1.0\,\mathrm{M}_\odot$, where the field predicts $6.0^{+0.8}_{-0.7}$ WDs, yet none are observed, with a probability of only $0.37\%$. Massive magnetic WDs show a similar deficit: only one of 20 cluster WDs with $M_{\mathrm{WD}}\geq1.0\,\mathrm{M}_\odot$ and $T_{\mathrm{eff}}\geq20{,}000\,{\rm K}$ is magnetic, compared with 10 of 16 in the field. Together, these deficits are consistent with an additional field population of massive merger remnants, particularly high-mass magnetic WDs and warm/hot DQs. Such objects may be underrepresented in clusters because young systems provide limited time for certain classes of delayed mergers, while older clusters lose members or dissolve; the field accumulates binary evolution products over Galactic timescales. Magnetic cluster WDs consistent with single-star evolution further suggest mass-dependent magnetic-field emergence, with fields appearing early in some massive WDs while young lower-mass WDs remain consistent with delayed emergence.
Comments25 pages, 17 figures, 4 tables. Submitted to ApJ
