碳AGB星雕龙R的孔径合成成像：对星盘上复杂结构和主要斑点的探测
Aperture synthesis imaging of the carbon AGB star R Sculptoris: Detection of a complex structure and a dominating spot on the stellar disk
摘要：
我们提出了近红外干涉测量的富碳渐近巨星分支（AGB）星R雕塑。可见度数据表明，一个广泛的圆形解决恒星盘与复杂的子结构。观测到的琥珀色平方可见度值在CO和CN带的位置显示下降，表明这些线形成于光球层上方的扩展层中。AMBER能见度值最适合无风模式。PIONIER数据与同一模型一致。我们得到的Rosseland角直径为8.9 ± 0.3质量，对应的Rosseland半径为355 ± 55 Rsun，有效温度为2640 ± 80 K，光度为log L/Lsun=3.74 ± 0.18。这些参数与初始质量1.5+-0.5 Msun和当前质量1.3+-0.7 Msun的演化轨迹相匹配。重建的PIONIER图像表现出复杂的结构内的恒星盘，包括一个占主导地位的亮点位于西部的恒星盘。该斑点的H波段峰值强度比边缘变暗校正后的星盘平均强度高出40%至60%。恒星盘面上最小和最大强度之间的对比度约为1：2.5。我们的观测结果与动态大气和风模型的预测大致一致，尽管有风的模型似乎有一个与我们的观测结果相比过于扩展的拱星包络。在星盘中发现的复杂结构很可能是由巨大的对流单体引起的，导致了大规模的激波锋面，以及它们对2-3个恒星半径距离上的光球层中的星团分子和尘埃形成的影响。
英文摘要：
We present near-infrared interferometry of the carbon-rich asymptotic giant branch (AGB) star R Sculptoris. The visibility data indicate a broadly circular resolved stellar disk with a complex substructure. The observed AMBER squared visibility values show drops at the positions of CO and CN bands, indicating that these lines form in extended layers above the photosphere. The AMBER visibility values are best fit by a model without a wind. The PIONIER data are consistent with the same model. We obtain a Rosseland angular diameter of 8.9+-0.3 mas, corresponding to a Rosseland radius of 355+-55 Rsun, an effective temperature of 2640+-80 K, and a luminosity of log L/Lsun=3.74+-0.18. These parameters match evolutionary tracks of initial mass 1.5+-0.5 Msun and current mass 1.3+-0.7 Msun. The reconstructed PIONIER images exhibit a complex structure within the stellar disk including a dominant bright spot located at the western part of the stellar disk. The spot has an H-band peak intensity of 40% to 60% above the average intensity of the limb-darkening-corrected stellar disk. The contrast between the minimum and maximum intensity on the stellar disk is about 1:2.5. Our observations are broadly consistent with predictions by dynamic atmosphere and wind models, although models with wind appear to have a circumstellar envelope that is too extended compared to our observations. The detected complex structure within the stellar disk is most likely caused by giant convection cells, resulting in large-scale shock fronts, and their effects on clumpy molecule and dust formation seen against the photosphere at distances of 2-3 stellar radii.
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