THE WHITE DWARFS WITHIN 25 pc OF THE SUN: KINEMATICS AND SPECTROSCOPIC SUBTYPES
THE WHITE DWARFS WITHIN 25 pc OF THE SUN: KINEMATICS AND SPECTROSCOPIC SUBTYPES
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DOI：
10.1088/0004-6256/147/6/129
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发表时间：
2014-01
期刊：
影响因子：
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通讯作者：
E. Sion;J. Holberg;T. Oswalt;G. Mccook;R. Wasatonic;Janine Myszka
中科院分区：
文献类型：
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作者：
E. Sion;J. Holberg;T. Oswalt;G. Mccook;R. Wasatonic;Janine Myszka
我们提出的光谱亚型的分数分布，表面温度的范围和分布，和运动学性质的白色矮星（WD）在25 pc的太阳。在224个WD的25个样品中，没有令人信服的证据表明存在晕圈WD。也没有什么证据表明在25 pc以内存在真正的厚盘子组件。看起来整个25 pc样本可能属于薄磁盘。我们也没有发现显着的运动学差异与光谱亚型。总DA非DA比的25 pc的样品是1.8，加深信封对流的表现，这将DA星足够薄的H表面层到非DA。我们将这一比例与其他研究的结果进行了比较。我们发现，至少有11%的WD在25 pc的太阳（DAZ和DZ星）的光球金属，可能源于吸积的拱星材料（碎片盘）在他们周围。如果这种解释是正确的，那么它表明类似百分比的行星，小行星状天体或碎片盘绕着它们运行的可能性。我们的体积有限的样品揭示了在Teff = 6000 K的DQ WD中众所周知的截止处的DC WD的堆积。考虑到小数字统计，我们推测其可能的进化意义。我们发现，在我们的体积有限的样品中，在25 pc样品中的磁性WD的发病率至少为8%，主要由冷WD。我们推导出近似的DB和DQ退化的形成率，并提出了一个初步的测试的进化方案，所有冷却DB星成为DQ WD通过氦对流疏浚与扩散尾的碳从他们的核心向上延伸。
We present the fractional distribution of spectroscopic subtypes, range and distribution of surface temperatures, and kinematical properties of the white dwarfs (WDs) within 25 pc of the Sun. There is no convincing evidence of halo WDs in the total 25 pc sample of 224 WDs. There is also little to suggest the presence of genuine thick disk subcomponent members within 25 pc. It appears that the entire 25 pc sample likely belongs to the thin disk. We also find no significant kinematic differences with respect to spectroscopic subtypes. The total DA to non-DA ratio of the 25 pc sample is 1.8, a manifestation of deepening envelope convection, which transforms DA stars with sufficiently thin H surface layers into non-DAs. We compare this ratio with the results of other studies. We find that at least 11% of the WDs within 25 pc of the Sun (the DAZ and DZ stars) have photospheric metals that likely originate from accretion of circumstellar material (debris disks) around them. If this interpretation is correct, then it suggests the possibility that a similar percentage have planets, asteroid-like bodies, or debris disks orbiting them. Our volume-limited sample reveals a pileup of DC WDs at the well-known cutoff in DQ WDs at Teff ∼ 6000 K. Mindful of small number statistics, we speculate on its possible evolutionary significance. We find that the incidence of magnetic WDs in the 25 pc sample is at least 8% in our volume-limited sample, dominated by cool WDs. We derive approximate formation rates of DB and DQ degenerates and present a preliminary test of the evolutionary scenario that all cooling DB stars become DQ WDs via helium convective dredge-up with the diffusion tail of carbon extending upward from their cores.