The Impact of White Dwarf Luminosity Profiles on Oscillation Frequencies
The Impact of White Dwarf Luminosity Profiles on Oscillation Frequencies
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DOI：
10.3847/2041-8213/aae70f
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发表时间：
2018-10
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影响因子：
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通讯作者：
Francis Timmes;R. Townsend;E. Bauer;A. Thoul;C. Fields;W. M. Wolf
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作者：
Francis Timmes;R. Townsend;E. Bauer;A. Thoul;C. Fields;W. M. Wolf
KIC 08626021是一颗最近引起相当大兴趣的脉动DB白色矮星（WD），也是开普勒对其脉动特性进行广泛监测的同类中的第一颗。将观测到的KIC 08626021的振荡频率拟合到一个模型中，可以深入了解其隐藏的内部结构。基于模板的WD模型选择光度分布，其中光度与封闭质量成比例，独立于有效温度Teff。演化模型的年轻WD与Teff 25，000 K表明，中微子发射引起的亮度配置文件与LR先生，我们探索这种对比，通过比较两个几乎相同的WD模型之间的振荡频率：一个与强制的亮度配置文件，和其他光度配置文件所确定的星星以前的演化历史。我们发现，低阶g模频率的差异高达70 μHz的开普勒观测范围内的KIC 08626021。这表明，通过忽略星星的适当热结构（例如，考虑到等离子体中微子损失的影响），通过使用轮廓计算的模型频率可能具有数十μHz水平的未校正的、有效的随机误差。基于线性外推的已发表结果，平均频率差为30 μHz，表明模板模型拟合精度的不确定性为WD质量的12%，半径的19%，以及中心氧质量分数的13%。
KIC 08626021 is a pulsating DB white dwarf (WD) of considerable recent interest, and the first of its class to be extensively monitored by Kepler for its pulsation properties. Fitting the observed oscillation frequencies of KIC 08626021 to a model can yield insights into its otherwise-hidden internal structure. Template-based WD models choose a luminosity profile where the luminosity is proportional to the enclosed mass, , independent of the effective temperature Teff. Evolutionary models of young WDs with Teff ≳ 25,000 K suggest that neutrino emission gives rise to luminosity profiles with Lr Mr. We explore this contrast by comparing the oscillation frequencies between two nearly identical WD models: one with an enforced luminosity profile, and the other with a luminosity profile determined by the star’s previous evolution history. We find that the low-order g-mode frequencies differ by up to ≃70 μHz over the range of Kepler observations for KIC 08626021. This suggests that by neglecting the proper thermal structure of the star (e.g., accounting for the effect of plasmon neutrino losses), the model frequencies calculated by using an profile may have uncorrected, effectively random errors at the level of tens of μHz. A mean frequency difference of 30 μHz, based on linearly extrapolating published results, suggests a template model uncertainty in the fit precision of ≃12% in WD mass, ≃9% in the radius, and ≃3% in the central oxygen mass fraction.