arXiv 2107.074472021-07-28astro-ph.SR

连续谱消除在识别Mira星周尘埃中的作用

The Effect of Continuum Elimination in Identifying Circumstellar Dust around Mira

Lisa M. Shepard, Angela K. Speck

备注：: 10 pages, 10 figures, published by the Monthly Notices of the Royal Astronomical Society 08 July 2021
DOI：: 10.1093/mnras/stab1944

摘要：

渐近巨星分支（AGB）恒星是宇宙尘埃的主要贡献者。通常，AGB恒星周围的尘埃是通过辐射转移（RT）建模，或通过简单的解构观察到的光谱。然而，所采用的方法各不相同。使用档案光谱，光度，和时间的原型尘埃星，米拉的数据，我们确定其星周硅酸盐尘埃颗粒。这是通过将观测到的光谱特征的位置和宽度与实验室数据相匹配来实现的。为了正确地进行这种比较，有必要考虑连续谱发射。在这里，我们调查的各种方式，在其中一个连续的观测光谱和它如何影响光谱特征的解释被淘汰。我们发现，虽然精确的连续体形状和温度不会对尘埃光谱特征的位置和形状产生关键影响，但重要的是要以特定的方式消除连续体。重要的是要了解什么有助于光谱，以消除连续的方式，允许与实验室光谱的候选尘埃物种进行比较。我们的方法适用于光学薄系统，如米拉。更高的光学深度将需要RT建模，这不能包括许多不同的潜在天体矿物，因为缺乏复杂的折射率。最后，我们发现，Mira所表现出的经典硅酸盐特征与真正的无定形硅酸盐本身并不一致，但可能最好用小的氧化铝贡献来解释，以匹配所观察到的10微米特征的FWHM。

英文摘要：

Asymptotic Giant Branch (AGB) stars are major contributors of cosmic dust to the universe. Typically, dust around AGB stars is investigated via radiative transfer (RT) modeling, or via simple deconstruction of observed spectra. However, methodologies applied vary. Using archival spectroscopic, photometric, and temporal data for the archetypal dusty star, Mira, we identify its circumstellar silicate dust grains. This is achieved by matching the positions and widths of observed spectral features with laboratory data. To do this comparison properly, it is necessary to account for the continuum emission. Here we investigate various ways in which a continuum is eliminated from observational spectra and how it affects the interpretation of spectral features. We find that while the precise continuum shapes and temperatures do not have a critical impact on the positions and shapes of dust spectral features, it is important to eliminate continua in a specific way. It is important to understand what contributes to the spectrum in order to remove the continuum in a way that allows comparison with laboratory spectra of candidate dust species. Our methodologies are applicable to optically thin systems, like that of Mira. Higher optical depths will require RT modeling, which cannot include many different potential astrominerals because there is a lack of complex refractive indices. Finally, we found that the classic silicate feature exhibited by Mira is not consistent with a real amorphous silicate alone but may be best explained with a small alumina contribution to match the observed FWHM of the 10 micron feature.

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