论文标题
Alma的景色,因此$ _2 $周围的氧气含量丰富的AGB星星
An ALMA view of SO and SO$_2$ around oxygen-rich AGB stars
论文作者
论文摘要
我们在与Alma的光谱线调查中对SO和SO $ _2 $进行了SO和SO _2 $,该量具有高的角度分辨率和敏感性,这是两个富含氧气的AGB恒星:低质量损失率R DOR和高质量损失率IK ik ik tau。我们分析了对这两个恒星的8行检测到的8行,78行SO _2 $对R DOR检测到,52行So $ _2 $检测到Ik Tau。我们检测到几行$^{34} $ SO,$^{33} $ SO和$^{34} $,因此$ _2 $ to to to to to to to to to to to to to to to to to to to to to r dor,因此s $^{18} $ o to r dor to r dor,因此这些物种的衍生同位素比率。空间分辨的观察结果表明,两种硫氧化物与r dor共同置于REDELLAR INVELOPE(CSE)中的相同风结构。大部分发射都以空间为中心的高斯丰度分布很好地再现。从较高的能源水平的发射以及$ _2 $到r dor的$ _2 $提供了证据,以支持早期工作中确定的气体旋转内部区域。新的观察结果使我们能够完善来自单个天线的先前观察结果的IK tau中SO的丰度分布,并确认分布类似于壳状,而分数丰度中的峰不在恒星上。确认不同类型的如此丰富的分布将有助于微调化学模型,并允许一种额外的方法来区分富氧AGB恒星的低质量和高质量降低速率。
We present and analyse SO and SO$_2$, recently observed with high angular resolution and sensitivity in a spectral line survey with ALMA, for two oxygen-rich AGB stars: the low mass-loss rate R Dor and high mass-loss rate IK Tau. We analyse 8 lines of SO detected towards both stars, 78 lines of SO$_2$detected towards R Dor and 52 lines of SO$_2$ detected towards IK Tau. We detect several lines of $^{34}$SO, $^{33}$SO and $^{34}$SO$_2$ towards both stars, and tentatively S$^{18}$O towards R Dor, and hence derive isotopic ratios for these species. The spatially resolved observations show us that the two sulphur oxides are co-located towards R Dor and trace out the same wind structures in the circumstellar envelope (CSE). Much of the emission is well reproduced with a Gaussian abundance distribution spatially centred on the star. Emission from the higher energy levels of SO and SO$_2$ towards R Dor provide evidence in support of a rotating inner region of gas identified in earlier work. The new observations allow us to refine the abundance distribution of SO in IK Tau derived from prior observations with single antennas, and confirm the distribution is shell-like with the peak in the fractional abundance not centred on the star. The confirmation of different types of SO abundance distributions will help fine-tune chemical models and allows for an additional method to discriminate between low and high mass-loss rates for oxygen-rich AGB stars.