论文标题
具有混合氢碳气氛的超质量白色矮人作为可能的合并残留物
An ultra-massive white dwarf with a mixed hydrogen-carbon atmosphere as a likely merger remnant
论文作者
论文摘要
白矮人是密集的，冷却恒星余烬，主要由碳和氧气组成，或氧气和霓虹灯（含量百分之几），在较高的初始恒星质量下。这些恒星岩心被氦壳包裹，而氦气通常被氢层包围，通常禁止直接观察内部组成。然而，在大量的白色矮人的一小部分的表面上观察到碳，有时还具有氧气痕迹，被认为是通过深氦对流区从核心挖出的。在这些物体中，仅发现氢的痕迹是因为预计大量氢会抑制包膜内的氢/氦对流混合。我们报告了WDJ055134.612+413531.09的识别，一种超质量（1.14 $ m_ \ odot $）的白矮人，具有独特的氢/碳混合气氛（C/H = 0.15的数量比）。我们对信封和内部的分析表明，总氢和氦质量分数必须比单星进化的预测低几个数量级：小于$ 10^{ - 9.5} $和$ 10^{ - 7.0} $。由于快速运动学（相对于当地静止的局部标准，$ 129 \ pm5 $ km/s），大质量和特殊的信封组成，我们认为WDJ0551+4135与紧密的binary System中两个白矮人合并的形成是一致的。
White dwarfs are dense, cooling stellar embers consisting mostly of carbon and oxygen, or oxygen and neon (with a few percent carbon) at higher initial stellar masses. These stellar cores are enveloped by a shell of helium which in turn is usually surrounded by a layer of hydrogen, generally prohibiting direct observation of the interior composition. However, carbon is observed at the surface of a sizeable fraction of white dwarfs, sometimes with traces of oxygen, and it is thought to be dredged-up from the core by a deep helium convection zone. In these objects only traces of hydrogen are found as large masses of hydrogen are predicted to inhibit hydrogen/helium convective mixing within the envelope. We report the identification of WDJ055134.612+413531.09, an ultra-massive (1.14 $M_\odot$) white dwarf with a unique hydrogen/carbon mixed atmosphere (C/H=0.15 in number ratio). Our analysis of the envelope and interior indicates that the total hydrogen and helium mass fractions must be several orders of magnitude lower than predictions of single star evolution: less than $10^{-9.5}$ and $10^{-7.0}$, respectively. Due to the fast kinematics ($129\pm5$ km/s relative to the local standard of rest), large mass, and peculiar envelope composition, we argue that WDJ0551+4135 is consistent with formation from the merger of two white dwarfs in a tight binary system.
