The 100 pc White Dwarf Sample in the SDSS Footprint
The 100 pc White Dwarf Sample in the SDSS Footprint
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DOI：
10.3847/1538-4357/ab9b8d
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发表时间：
2020-05
期刊：
影响因子：
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通讯作者：
M. Kilic;P. Bergeron;A. Kosakowski;Warren R. Brown;M. Agueros;S. Blouin
中科院分区：
文献类型：
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作者：
M. Kilic;P. Bergeron;A. Kosakowski;Warren R. Brown;M. Agueros;S. Blouin
我们给出了100pC内711颗白矮星的后续光谱分析，并给出了斯隆数字天空勘测足迹中100pC白矮星样本的详细大气分析。我们完成了83%的白矮星的光谱跟踪，这些白矮星的温度高于6000K，其中大气成分可以得到可靠的约束。我们在纯氢大气中发现了1508DA的白矮星。DA质量分布在0.59M⊙处有一个极窄的峰值，显示了质量相对较大的白矮星的肩部，M=0.7-0.9M⊙。将这一分布与双星群合成模型进行比较，我们发现，通过合并形成的单星的贡献无法解释质量较大的白矮星数量过多的原因。此外，冷Das的质量分布显示几乎没有M>；1M⊙白矮星。0.7M-0.9M⊙的堆积和M>；1M⊙白矮星的消失与岩心结晶的作用相一致。尽管进化模型正确地预测了堆积的位置，但结晶潜热本身的延迟不足以产生显著的堆积，而且由于相分离等相关效应而产生的额外冷却延迟是必要的。我们还讨论了红外微弱(超冷)白矮星的数量，并首次证明了存在一个定义明确的颜色和星等序列。奇怪的是，这一序列与颜色-星等图中的一个区域有关，在那里，氦占主导地位的白矮星的数量很少。这表明这些红外线微弱的白矮星可能有混合的H/He大气。
We present follow-up spectroscopy of 711 white dwarfs within 100 pc, and we present a detailed model atmosphere analysis of the 100 pc white dwarf sample in the Sloan Digital Sky Survey footprint. Our spectroscopic follow-up is complete for 83% of the white dwarfs hotter than 6000 K, where the atmospheric composition can be constrained reliably. We identify 1508 DA white dwarfs with pure hydrogen atmospheres. The DA mass distribution has an extremely narrow peak at 0.59 M⊙ and reveals a shoulder from relatively massive white dwarfs with M = 0.7–0.9 M⊙. Comparing this distribution with binary population synthesis models, we find that the contribution from single stars that form through mergers cannot explain the overabundance of massive white dwarfs. In addition, the mass distribution of cool DAs shows a near absence of M > 1 M⊙ white dwarfs. The pile-up of 0.7–0.9 M⊙ and the disappearance of M > 1 M⊙ white dwarfs is consistent with the effects of core crystallization. Even though the evolutionary models predict the location of the pile-up correctly, the delay from the latent heat of crystallization by itself is insufficient to create a significant pile-up, and additional cooling delays from related effects like phase separation are necessary. We also discuss the population of infrared-faint (ultracool) white dwarfs and demonstrate for the first time the existence of a well-defined sequence in color and magnitude. Curiously, this sequence is connected to a region in the color–magnitude diagrams where the number of white dwarfs with a helium-dominated atmosphere is low. This suggests that the infrared-faint white dwarfs likely have mixed H/He atmospheres.