Serendipitous Discovery of Nine White Dwarfs with Gaseous Debris Disks
Serendipitous Discovery of Nine White Dwarfs with Gaseous Debris Disks
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DOI：
10.3847/1538-4357/abbdfa
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发表时间：
2020-10
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影响因子：
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通讯作者：
C. Melis;B. Klein;A. E. Doyle;A. Weinberger;B. Zuckerman;P. Dufour
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作者：
C. Melis;B. Klein;A. E. Doyle;A. Weinberger;B. Zuckerman;P. Dufour
光学光谱观测的白色矮星选自目录的基础上盖亚DR 2数据库揭示了9个新的气体碎片盘，轨道单一的白色矮星，约2倍的增加，比以前已知的样本。对于每个来源，我们提出了气体排放线确定和基本的恒星参数，包括低分辨率光谱线的丰度。主要发现包括（1）最冷的白色矮星这颗星星WD 0145 +234据报道最近经历了一次红外爆发;（2）多个元素的气体发射在速度空间中处于同一位置，表明不同元素混合良好;（3）对SDSS J 0006 +2858具有高度不对称的发射结构，并且对另外两个系统可能具有不对称的发射结构;（4）由大约25%的DB和75%的DA白色矮星组成的总体样品，与实地种群中发现的主要大气类型的总体分布相一致;（5）在Gaia J 0611 −6931的光谱中从未见过的来自Na的发射线，朝向WD 0842+572的半禁Mg、Ca和Fe线，以及两颗恒星中的Si。目前已知的气体碎片盘系统样本明显偏向北方半球的恒星，这表明在南半球有十几颗发射线恒星等待被发现。
Optical spectroscopic observations of white dwarf stars selected from catalogs based on the Gaia DR2 database reveal nine new gaseous debris disks that orbit single white dwarf stars, about a factor of 2 increase over the previously known sample. For each source we present gas emission lines identified and basic stellar parameters, including abundances for lines seen with low-resolution spectroscopy. Principle discoveries include (1) the coolest white dwarf (Teff ≈ 12,720 K) with a gas disk; this star, WD0145+234, has been reported to have undergone a recent infrared outburst; (2) co-location in velocity space of gaseous emission from multiple elements, suggesting that different elements are well mixed; (3) highly asymmetric emission structures toward SDSS J0006+2858, and possibly asymmetric structures for two other systems; (4) an overall sample composed of approximately 25% DB and 75% DA white dwarfs, consistent with the overall distribution of primary atmospheric types found in the field population; and (5) never-before-seen emission lines from Na in the spectra of Gaia J0611−6931, semi-forbidden Mg, Ca, and Fe lines toward WD 0842+572, and Si in both stars. The currently known sample of gaseous debris disk systems is significantly skewed toward northern hemisphere stars, suggesting a dozen or so emission line stars are waiting to be found in the southern hemisphere.