文章基本信息

标题：Molecular line study of the S-type AGB star W Aquilae
其他标题：ALMA observations of CS, SiS, SiO and HCN
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作者：M. Brunner ; T. Danilovich ; S. Ramstedt 等
期刊名称：Astronomy & Astrophysics
印刷版ISSN：0004-6361
电子版ISSN：1432-0746
出版年度：2018
卷号：617
DOI：10.1051/0004-6361/201832724
语种：English
出版社：EDP Sciences
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 ande-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.
关键词：enstars: abundancesstars: AGB and post-AGBcircumstellar matterstars: mass-lossstars: winds, outflowssubmillimeter: stars