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arXiv 2405.02423astro-ph.SR
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利用宽距白矮星+白矮星双星对白矮星光谱年龄估计的检验

A Test of Spectroscopic Age Estimates of White Dwarfs using Wide WD+WD Binaries

Tyler M. Heintz, J. J. Hermes, P. -E. Tremblay, Lou Baya Ould Rouis, Joshua S. Redding, B. C. Kaiser, Jennifer L. van Saders

AI总结:

本文通过宽距双白矮星样本检验光谱与测光年龄估计的可靠性,发现光谱拟合未显著改善年龄一致性,且测光参数对DA白矮星年龄一致性更优,并揭示约20%的宽距双星可能经历并合。

摘要:

白矮星数十年来一直被用作精确且准确的年龄指示器。本工作对在可获得光谱观测时白矮星总年龄的可靠性进行了检验。我们对宽距双白矮星(WD+WD)双星中的148颗独立白矮星进行了后续光谱观测。我们用264条先前发表的白矮星光谱以及从Gaia XP光谱推断出的1292个高置信度白矮星光谱型补充了样本。我们发现,对光学光谱的光谱拟合并未显著改善宽距WD+WD双星中白矮星之间年龄一致性。对于每颗白矮星总年龄不确定性小于20%的白矮星对,无论是通过测光还是光谱确定的总年龄,年龄一致性的中位数均为约1.5σ。对于DA型白矮星,我们进一步发现,通过光谱能量分布拟合测光确定的大气参数比通过巴耳末线拟合光谱确定的参数具有更好的总年龄一致性(分别为1.0σ、0.2 Gyr或双星平均总年龄的14%,而光谱确定的一致性为1.5σ、0.3 Gyr或双星平均总年龄的28%)。我们发现了宽距WD+WD双星中存在显著并合比例的证据:在多个经光谱识别的样本中,约20%与单调递增的初始-最终质量关系不一致。我们建议获取识别光谱,以确保在测光拟合中使用正确的大气模型,从而确定白矮星最准确的总年龄。

英文摘要:

White dwarf stars have been used for decades as precise and accurate age indicators. This work presents a test of the reliability of white dwarf total ages when spectroscopic observations are available. We conduct follow-up spectroscopy of 148 individual white dwarfs in widely separated double-white-dwarf (WD+WD) binaries. We supplement the sample with 264 previously published white dwarf spectra, as well as 1292 high-confidence white dwarf spectral types inferred from their Gaia XP spectra. We find that spectroscopic fits to optical spectra do not provide noticeable improvement to the age agreement among white dwarfs in wide WD+WD binaries. The median age agreement is $\approx$$1.5σ$ for both photometrically and spectroscopically determined total ages, for pairs of white dwarfs with each having a total age uncertaintiy $<$ 20\%. For DA white dwarfs, we further find that photometrically determined atmospheric parameters from spectral energy distribution fitting give better total age agreement ($1.0σ$, 0.2 Gyr, or 14\% of the binary's average total age) compared to spectroscopically determined parameters from Balmer-line fits (agreement of $1.5σ$, 0.3 Gyr, or 28\% of binary's average total age). We find further evidence of a significant merger fraction among wide WD+WD binaries: across multiple spectroscopically identified samples, roughly 20\% are inconsistent with a monotonically increasing initial-final mass relation. We recommend the acquisition of an identification spectrum to ensure the correct atmospheric models are used in photometric fits in order to determine the most accurate total age of a white dwarf star.

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