A Search for Pulsations in Helium White Dwarfs
A Search for Pulsations in Helium White Dwarfs
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DOI：
10.1086/663865
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发表时间：
2011-05
影响因子：
3.5
通讯作者：
J. Steinfadt;L. Bildsten;D. Kaplan;B. Fulton;S. Howell;T. Marsh;E. Ofek;Avi Shporer
中科院分区：
文献类型：
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作者：
J. Steinfadt;L. Bildsten;D. Kaplan;B. Fulton;S. Howell;T. Marsh;E. Ofek;Avi Shporer
最近大量的巡天，特别是斯隆数字巡天，已经发现了许多低质量（M < 0.45 M）的白色矮星，它们的核心应该是由接近纯氦组成的。这些WDs有两种类型：质量为0.2 < M < 0.45 M的WDs，其氢包层非常薄，以至于它们迅速冷却;质量为M < 0.2 M的WDs（通常称为极低质量[ELM] WDs），其氢包层足够厚，可以维持109年的氢燃烧。在这两种情况下，这些WD通过ZZ Ceti不稳定带，Teff为9000- 12，000 K，其中g模式脉动总是发生在碳/氧WD中。这种期望，再加上理论工作的对比C/O和氦核心WD，激励我们寻找脉动在12个良好的特点氦WD。我们在此报告，我们未能找到我们的样品中的任何干扰因素。虽然我们有不同的振幅限制，但似乎需要更仔细地考虑这些物体中关于脉动开始的理论预期。我们关闭鼓励新的他WD样品成为可用的额外的观察，我们推测在理论上的工作可能需要。
The recent plethora of sky surveys, especially the Sloan Digital Sky Survey, have discovered many low-mass (M < 0.45 M⊙) white dwarfs that should have cores made of nearly pure helium. These WDs come in two varieties: those with masses 0.2 < M < 0.45 M⊙ and H envelopes so thin that they rapidly cool and those with M < 0.2 M⊙ (often called extremely low mass [ELM] WDs) that have thick enough H envelopes to sustain 109 yr of H burning. In both cases, these WDs evolve through the ZZ Ceti instability strip, Teff ≈ 9000–12,000 K, where g-mode pulsations always occur in carbon/oxygen WDs. This expectation, plus theoretical work on the contrasts between C/O and He-core WDs, motivated our search for pulsations in 12 well-characterized helium WDs. We report here on our failure to find any pulsators among our sample. Though we have varying amplitude limits, it appears likely that the theoretical expectations regarding the onset of pulsations in these objects require closer consideration. We close by encouraging additional observations as new He WD samples become available, and we speculate on where theoretical work may be needed.