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首页> 外文期刊>Astronomy and astrophysics >Simplified models of stellar wind anatomy for interpreting high-resolution data - Analytical approach to embedded spiral geometries
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Simplified models of stellar wind anatomy for interpreting high-resolution data - Analytical approach to embedded spiral geometries

机译：解释高分辨率数据的恒星风解剖学简化模型-嵌入螺旋几何的解析方法

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Context. Recent high-resolution observations have shown that stellar winds harbour complexities that strongly deviate from spherical symmetry, which generally is assumed as standard wind model. One such morphology is the Archimedean spiral, which is generally believed to be formed by binary interactions, as has been directly observed in multiple sources. Aims. We seek to investigate the manifestation in the observables of spiral structures embedded in the spherical outflows of cool stars. We aim to provide an intuitive bedrock with which upcoming ALMA data can be compared and interpreted. Methods. By means of an extended parameter study, we modelled rotational CO emission from the stellar outflow of asymptotic giant branch stars. To this end, we developed a simplified analytical parametrised description of a 3D spiral structure. This model is embedded into a spherical wind and fed into the 3D radiative transfer code LIME, which produces 3D intensity maps throughout velocity space. Subsequently, we investigated the spectral signature of rotational transitions of CO in the models, as well as the spatial aspect of this emission by means of wide-slit position-velocity (PV) diagrams. Additionally, we quantified the potential for misinterpreting the 3D data in a 1D context. Finally, we simulated ALMA observations to explore the effect of interferometric noise and artefacts on the emission signatures. Results. The spectral signatures of the CO rotational transition v = 0J = 3 ? 2 are very efficient at concealing the dual nature of the outflow. Only a select few parameter combinations allow for the spectral lines to disclose the presence of the spiral structure. If the spiral cannot be distinguished from the spherical signal, this might result in an incorrect interpretation in a 1D context. Consequently, erroneous mass-loss rates would be calculated. The magnitude of these errors is mainly confined to a factor of a few, but in extreme cases can exceed an order of magnitude. CO transitions of different rotationally excited levels show a characteristical evolution in their line shape that can be brought about by an embedded spiral structure. However, if spatial information on the source is also available, the use of wide-slit PV diagrams systematically expose the embedded spiral. The PV diagrams also readily provide most of the geometrical and physical properties of the spiral-harbouring wind. Simulations of ALMA observations prove that the choice of antenna configuration is strongly dependent on the geometrical properties of the spiral. We conclude that exploratory endeavours should observe the object of interest with a range of different maximum-baseline configurations.
机译：上下文。最近的高分辨率观测表明，恒星风的复杂性大大偏离了球形对称性，而球形对称性通常被认为是标准风模型。一种这样的形态是阿基米德螺线，通常认为它是由二元相互作用形成的，正如在多种来源中直接观察到的那样。目的我们试图调查嵌入在冷恒星球形流出中的螺旋结构的可观测性的表现。我们旨在提供一个直观的基石，通过它可以比较和解释即将到来的ALMA数据。方法。通过扩展参数研究，我们对渐近巨型分支星的恒星流出的旋转CO排放进行了建模。为此，我们开发了3D螺旋结构的简化分析参数化描述。该模型嵌入到球形风中，并馈入3D辐射传递代码LIME，该代码在整个速度空间中生成3D强度图。随后，我们通过宽缝位置-速度（PV）图研究了模型中CO旋转跃迁的光谱特征，以及这种排放的空间特征。此外，我们量化了在1D上下文中误解3D数据的可能性。最后，我们模拟了ALMA观察结果，以探索干涉噪声和伪影对发射特征的影响。结果。 CO旋转跃迁的光谱特征v = 0J = 3？ 2在掩盖流出的双重性质方面非常有效。只有少数几个参数组合允许光谱线揭示螺旋结构的存在。如果无法从球面信号中分辨出螺旋线，则可能导致在一维上下文中的错误解释。因此，将计算出错误的质量损失率。这些误差的大小主要限制在几个因素之内，但在极端情况下可能会超过一个数量级。不同的旋转激发能级的CO跃迁在其线形中表现出特征性的演化，这可由嵌入的螺旋结构引起。但是，如果还可以获得源的空间信息，则使用宽缝PV图可以系统地暴露嵌入式螺旋。 PV图还可以轻松提供螺旋风的大多数几何和物理特性。 ALMA观测值的模拟证明，天线配置的选择很大程度上取决于螺旋的几何特性。我们得出结论，探索性的努力应该以一系列不同的最大基线配置来观察目标对象。

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