arXiv 2103.069062021-03-11astro-ph.SR

太阳附近最大质量的白矮星

The Most Massive White Dwarfs in the Solar Neighborhood

Mukremin Kilic, P. Bergeron, Simon Blouin, A. Bedard

备注：: MNRAS, in press
DOI：: 10.1093/mnras/stab767

摘要：

我们提出了一个蒙特利尔白矮星数据库100 pc样本中最大质量的白矮星候选者的分析。我们确定了25个对象，将是更大的质量比$1.3~M_{\odot}$，如果他们有纯H大气和CO核心，包括两个异常高光度质量估计附近的Ekrasekhar极限。我们提供了这两颗白矮星的后续光谱，并表明它们确实明显低于这个极限。我们将CO核白矮星的模型计算扩展到$M=1.334\ M_\odot$，这对应于我们的状态方程表的高密度极限，$ρ= 10^9$ g cm $^{-3}$。我们发现许多物体接近我们的CO核心模型的最大质量。据预测，相当一部分超大质量白矮星是通过双星合并形成的。合并种群可以通过它们的运动学、磁性或快速旋转率来揭示自己。我们确定了四个横向速度异常值，四个可能的磁性白矮星（其中一个也是横向速度异常值），一个快速旋转，表明我们样本中的25个超大质量白矮星中至少有8个可能是合并产物。

英文摘要：

We present an analysis of the most massive white dwarf candidates in the Montreal White Dwarf Database 100 pc sample. We identify 25 objects that would be more massive than $1.3~M_{\odot}$ if they had pure H atmospheres and CO cores, including two outliers with unusually high photometric mass estimates near the Chandrasekhar limit. We provide follow-up spectroscopy of these two white dwarfs and show that they are indeed significantly below this limit. We expand our model calculations for CO core white dwarfs up to $M=1.334\ M_\odot$, which corresponds to the high-density limit of our equation-of-state tables, $ρ= 10^9$ g cm$^{-3}$. We find many objects close to this maximum mass of our CO core models. A significant fraction of ultramassive white dwarfs are predicted to form through binary mergers. Merger populations can reveal themselves through their kinematics, magnetism, or rapid rotation rates. We identify four outliers in transverse velocity, four likely magnetic white dwarfs (one of which is also an outlier in transverse velocity), and one with rapid rotation, indicating that at least 8 of the 25 ultramassive white dwarfs in our sample are likely merger products.

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