根据近红外干涉测量和光谱能量分布精确确定老人星的基本参数
Refined fundamental parameters of Canopus from combined near-IR interferometry and spectral energy distribution
摘要：
老人星是太阳系中最明亮、最接近太阳系的黄色超巨星，它为理解大质量恒星演化的物理学提供了一个独特的实验室。准确和精确的PIONIER数据使我们能够使用不同的分析定律同时测量角直径和临边暗化（LD）轮廓。我们发现，幂律LD，也与恒星大气模型的预测一致，再现干涉数据。对于这个模型，我们测量了$7.184 \pm 0.0017 \pm 0.029$ mas的角直径和$0.1438 \pm 0.0015$的LD系数，它们分别是$\gtrsim 5$和$\sim15-25$，比我们之前2008年关于老人星的A\A论文更精确。从一个专门的干涉数据分析，我们还提供了新的限制弱表面不均匀性的假定存在。此外，我们分析了SED在一个创新的方式，同时拟合红化相关的参数和恒星的有效温度和重力。我们发现，基于两个有效温度的模型是更好地再现整个SED，从中我们得出了几个参数，包括一个新的热通量估计。在这项工作中，PIONIER测量的老人星角直径和LD是迄今为止最精确的，对几个相关的基本参数有直接影响。此外，由于我们的联合分析，我们能够确定一组基本参数，同时再现高精度的干涉数据和良好的质量SED，并在同一时间，同意恒星演化模型。
英文摘要：
Canopus, the brightest and closest yellow supergiant to our Solar System, offers a unique laboratory for understanding the physics of evolved massive stars. The accurate and precise PIONIER data allowed us to simultaneously measure the angular diameter and the limb darkening (LD) profile using different analytical laws. We found that the power-law LD, being also in agreement with predictions from stellar atmosphere models, reproduces the interferometric data well. For this model we measured an angular diameter of $7.184 \pm 0.0017 \pm 0.029$ mas and an LD coefficient of $0.1438 \pm 0.0015$, which are respectively $\gtrsim 5$ and $\sim15-25$ more precise than in our previous A\&A paper on Canopus from 2008. From a dedicated analysis of the interferometric data, we also provide new constraints on the putative presence of weak surface inhomogeneities. Additionally, we analyzed the SED in a innovative way by simultaneously fitting the reddening-related parameters and the stellar effective temperature and gravity. We find that a model based on two effective temperatures is much better at reproducing the whole SED, from which we derived several parameters, including a new bolometric flux estimate. The Canopus angular diameter and LD measured in this work with PIONIER are the most precise to date, with a direct impact on several related fundamental parameters. Moreover, thanks to our joint analysis, we were able to determine a set of fundamental parameters that simultaneously reproduces both high-precision interferometric data and a good quality SED and, at the same time, agrees with stellar evolution models.
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