天鹰座W星S-型AGB的分子线研究CS、SiS、SiO和HCN的ALMA观察结果
Molecular line study of the S-type AGB star W Aquilae. ALMA observations of CS, SiS, SiO and HCN
摘要：
上下文凭借阿塔卡马大型毫米/亚毫米阵列（ALMA）出色的空间分辨率和灵敏度，可以在演化恒星周围的星周包层（CSE）中观察和分辨除了丰富的CO之外的分子气体，例如双星S型渐近巨分支（AGB）星W Aquilae。目的。我们的目标是约束的CSE的化学成分，并确定径向丰度分布，光球峰值丰度，和同位素比值的选择化学上重要的分子物种在最里面的CSE的W Aql。推导出的参数的背景下，AGB星的化学演化，并与理论模型进行比较。方法.我们采用一维辐射转移建模-与加速λ迭代（ALI）辐射转移代码-的径向丰度分布的总共五个分子种类（CS，SiS，30 SiS，29 SiO和H13 CN），并确定最佳拟合模型参数的基础上，高分辨率ALMA观测以及存档单碟观测。空间分辨ALMA观测的另一个优点是，我们可以直接从观测中约束观测到的谱线跃迁的径向轮廓。结果我们推导出CS，SiS，30 SiS，29 SiO和H13 CN的丰度和e-折叠半径，并将其与以前的研究进行比较，这些研究仅基于未分辨的单碟光谱。我们的结果与以前的结果一致，并且由于发射区域的分辨率而更准确。
英文摘要：
Context. With the outstanding spatial resolution and sensitivity of the Atacama Large Millimeter/sub-millimeter Array (ALMA), molecular gas other than the abundant CO can be observed and resolved in circumstellar envelopes (CSEs) around evolved stars, such as the binary S-type Asymptotic Giant Branch (AGB) star W Aquilae. Aims. We aim to constrain the chemical composition of the CSE and determine the radial abundance distribution, the photospheric peak abundance, and isotopic ratios of a selection of chemically important molecular species in the innermost CSE of W Aql. The derived parameters are put into the context of the chemical evolution of AGB stars and are compared with theoretical models. Methods. We employ one-dimensional radiative transfer modeling - with the accelerated lambda iteration (ALI) radiative transfer code - of the radial abundance distribution of a total of five molecular species (CS, SiS, 30SiS, 29SiO and H13CN) and determine the best fitting model parameters based on high-resolution ALMA observations as well as archival single-dish observations. The additional advantage of the spatially resolved ALMA observations is that we can directly constrain the radial profile of the observed line transitions from the observations. Results. We derive abundances and e-folding radii for CS, SiS, 30SiS, 29SiO and H13CN and compare them to previous studies, which are based only on unresolved single-dish spectra. Our results are in line with previous results and are more accurate due to resolution of the emission regions.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
