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arXiv 2410.14014astro-ph.SR
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白矮星冷却年龄测定中系统不确定性的量化

Quantifying systematic uncertainties in white dwarf cooling age determinations

Praneet Pathak, Simon Blouin, Falk Herwig

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Accepted by ApJ
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AI总结：

本文利用 MESA 模拟量化了白矮星冷却年龄测定中由模型输入假设引起的系统不确定性，并提供了基于有效温度和质量评估该不确定性的结果表。

摘要：

白矮星的冷却年龄通常通过将有效温度和质量映射到演化模型中的年龄来确定。通常，所报告的冷却年龄不确定性仅考虑光谱或光度测定得到的 $T_{\rm eff}$ 和质量的误差传播。然而，冷却模型本身也存在不确定性，因为它们依赖于许多约束不足的输入。本文估计了这些系统性模型不确定性。我们使用 MESA 生成 $0.5-1.0 M_{\odot}$ 的氢大气碳氧核心白矮星的冷却序列，并在其核心化学分层、氦包层厚度、氢含量以及计算中所采用的导电不透明度方面采用不同假设。所探索的参数空间受到各种恒星演化模型预测值以及星震学研究推断值的范围约束。对于一颗 $0.6 M_{\odot}$ 的白矮星，我们发现在 10,000 K 时不确定性为 0.03 Gyr（对应 5% 的相对不确定性），在 4000 K 时为 0.8 Gyr（9%）。这一不确定性是显著的，因为它与一颗典型白矮星通过传播 $T_{\rm eff}$ 和质量测量误差所得到的年龄不确定性相当。我们还单独考虑了 $^{22}$Ne 壳层蒸馏的潜在影响，它可能给已结晶白矮星带来约 $\sim 1$ Gyr 的额外不确定性。我们提供了模拟结果表，可用于根据白矮星的 $T_{\rm eff}$ 和质量评估系统性模型不确定性。我们鼓励在所有未来测量白矮星冷却年龄的研究中使用该表。

英文摘要：

Cooling ages of white dwarfs are routinely determined by mapping effective temperatures and masses to ages using evolutionary models. Typically, the reported uncertainties on cooling ages only consider the error propagation of the uncertainties on the spectroscopically or photometrically determined $T_{\rm eff}$ and mass. However, cooling models are themselves uncertain, given their dependence on many poorly constrained inputs. This paper estimates these systematic model uncertainties. We use MESA to generate cooling sequences of $0.5-1.0 M_{\odot}$ hydrogen-atmosphere white dwarfs with carbon-oxygen cores under different assumptions regarding the chemical stratification of their core, the thickness of their helium envelope, their hydrogen content, and the conductive opacities employed in the calculations. The parameter space explored is constrained by the range of values predicted by a variety of stellar evolution models and inferred from asteroseismological studies. For a $0.6 M_{\odot}$ white dwarf, we find an uncertainty of 0.03 Gyr at 10,000 K (corresponding to a 5% relative uncertainty) and 0.8 Gyr at 4000 K (9%). This uncertainty is significant, as it is comparable to the age uncertainty obtained by propagating the measurement errors on $T_{\rm eff}$ and mass for a typical white dwarf. We also separately consider the potential impact of $^{22}$Ne shell distillation, which plausibly leads to an additional uncertainty of $\sim 1$ Gyr for crystallized white dwarfs. We provide a table of our simulation results that can be used to evaluate the systematic model uncertainty based on a white dwarf's $T_{\rm eff}$ and mass. We encourage its use in all future studies where white dwarf cooling ages are measured.

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