Seven white dwarfs with circumstellar gas discs I: white dwarf parameters and accreted planetary abundances
Seven white dwarfs with circumstellar gas discs I: white dwarf parameters and accreted planetary abundances
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七颗具有星周气体盘的白矮星 I：白矮星参数和吸积行星丰度
DOI：
10.1093/mnras/stad3557
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发表时间：
2023
影响因子：
4.8
通讯作者：
Melis, C.
中科院分区：
文献类型：
--
作者：
Rogers, L. K.;Bonsor, A.;Xu, S.;Dufour, P.;Klein, B. L.;Buchan, A.;Hodgkin, S.;Hardy, F.;Kissler-Patig, M.;Melis, C.
对污染白矮星大气层的行星物质的观测是探索系外物质整体组成的重要手段。给出了7颗已知星际尘埃和气体排放的白矮星的中、高分辨率光学和紫外光谱。测量了C、O、Na、S、P、镁、铝、硅、钙、钛、铬、铁和镍的光球吸收线的探测或有意义的上限。对于已知可观测到的气体发射盘(以及测量的光球层丰度)的16颗白矮星，没有证据表明它们的吸积率平均与那些没有探测到气体发射的白矮星不同。这表明，通常情况下，吸积不会因气体阻力而增强。在白矮星的有效温度范围内(16 0 0 0-2 5 0 0 0 K)，从光谱白矮星参数和光度学白矮星参数得到的元素丰度比绝对丰度更一致。最重要的是，这凸显了白矮星参数的不确定性并没有阻止白矮星被用来研究行星的组成。这三颗以氢为主的白矮星的氧和硅的丰度因它们是来自光学光谱还是来自紫外光谱而不同，它们的光学光谱和紫外光谱的丰度相差0.62 dex。这种光学/紫外线差异可能与形成谱线的大气深度不同有关；需要对白矮星大气模型进行进一步研究才能理解这种差异。
Observations of planetary materialpollutingthe atmospheres of white dwarfs are an important probe of the bulk composition of exoplanetary material. Medium- and high-resolution optical and ultraviolet spectroscopy of seven white dwarfs with known circumstellar dust and gas emission are presented. Detections or meaningful upper limits for photospheric absorption lines are measured for: C, O, Na, S, P, Mg, Al, Si, Ca, Ti, Cr, Fe, and Ni. For 16 white dwarfs with known observable gaseous emission discs (and measured photospheric abundances), there is no evidence that their accretion rates differ, on average, from those without detectable gaseous emission. This suggests that, typically, accretion is not enhanced by gas drag. At the effective temperature range of the white dwarfs in this sample (16 000–25 000 K) the abundance ratios of elements are more consistent than absolute abundances when comparing abundances derived from spectroscopic white dwarf parameters versus photometric white dwarf parameters. Crucially, this highlights that the uncertainties on white dwarf parameters do not prevent white dwarfs from being utilized to study planetary composition. The abundances of oxygen and silicon for the three hydrogen-dominated white dwarfs in the sample with both optical and ultraviolet spectra differ by 0.62 dex depending on if they are derived from the optical or ultraviolet spectra. This optical/ultraviolet discrepancy may be related to differences in the atmospheric depth of line formation; further investigations into the white dwarf atmospheric modelling are needed to understand this discrepancy.