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arXiv 2408.01411astro-ph.SRastro-ph.GA
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暗弱行星状星云核的光谱巡天 VI. 十七颗富氢中心星

Spectroscopic survey of faint planetary-nebula nuclei VI. Seventeen hydrogen-rich central stars

Nicole Reindl, Howard E. Bond, Klaus Werner, Gregory R. Zeimann

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accepted for publication in A&A
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AI总结：

本文基于10米Hobby-Eberly望远镜光谱巡天，利用NLTE模型大气首次系统分析了17颗富氢行星状星云中心星的物理参数，并结合光变曲线和光谱能量分布探讨其演化阶段及红外超来源。

摘要：

我们呈现了对17颗富氢行星状星云（PNe）中心星的分析，这些天体是在10米Hobby-Eberly望远镜上开展的暗弱银河系PNe核光谱巡天中观测到的。我们的样本包括10颗O(H)型星、4颗DAO白矮星（WDs）、2颗DA白矮星和1颗sdOB星。光谱通过非局部热动平衡（NLTE）模型大气进行分析，使我们能够推导出中心星的有效温度、表面重力和氦丰度。其中16颗为首次分析，使通过NLTE大气建模获得参数的富氢热中心星数量增加了约20%。我们重点介绍了一颗罕见的热DA白矮星中心星Abell 24，其有效温度$T_\mathrm{eff}$可能超过100kK，以及sdOB星Pa 3异常高的引力质量$0.70 \pm 0.05 \mathrm{M}_\odot$，该值显著高于极端水平支星的标准质量$\approx 0.48\\,\mathrm{M}_{\odot}$。通过研究Zwicky Transient Facility的光变曲线（我们15个北方天体的数据可用），我们发现它们均未表现出大于百分之几星等的周期性测光变化。这可能表明我们的样本主要代表了单星从渐近巨星支演化到白矮星的标准演化过程中最热的阶段。我们还检查了光谱能量分布，在6个天体中探测到红外超，这可能是由于晚型伴星或热（$\approx 10^3$ K）和/或冷（$\approx 100$ K）尘埃所致。我们证实了此前的发现，即光谱距离通常高于通过Gaia天体测量得到的距离，这一差异值得系统性地研究。

英文摘要：

We present an analysis of 17 H-rich central stars of planetary nebulae (PNe) observed in our spectroscopic survey of nuclei of faint Galactic PNe carried out at the 10-m Hobby-Eberly Telescope. Our sample includes ten O(H) stars, four DAO white dwarfs (WDs), two DA WDs, and one sdOB star. The spectra were analyzed by means of NLTE model atmospheres, allowing us to derive the effective temperatures, surface gravities, and He abundances of the central stars. Sixteen of them were analyzed for the first time, increasing the number of hot H-rich central stars with parameters obtained through NLTE atmospheric modeling by approximately 20%. We highlight a rare hot DA WD central star, Abell 24, which has a $T_\mathrm{eff}$ likely in excess of 100kK, as well as the unusually high gravity mass of $0.70 \pm 0.05 \mathrm{M}_\odot$ for the sdOB star Pa 3, which is significantly higher than the canonical extreme horizontal-branch star mass of $\approx 0.48\,\mathrm{M}_{\odot}$. By investigating Zwicky Transient Facility light curves, which were available for our 15 northern objects, we found none of them show a periodic photometric variability larger than a few hundredths of a magnitude. This could indicate that our sample mainly represents the hottest phase during the canonical evolution of a single star when transitioning from an asymptotic giant branch star into a WD. We also examined the spectral energy distributions, detecting an infrared excess in six of the objects, which could be due to a late-type companion or to hot ($\approx 10^3$ K) and\or cool ($\approx 100$ K) dust. We confirm previous findings that spectroscopic distances are generally higher than found through Gaia astrometry, a discrepancy that deserves to be investigated systematically.

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