AI 中文总结
本研究利用SPHERE/ZIMPOL对45颗近邻AGB星进行高角分辨率偏振观测，构建编目，探测到16个尘埃包层，训练随机森林模型确定区分变量，为观测目标选择和星周包层演化研究提供支撑。
AI 中文摘要
我们提供了迄今最大的渐近巨星支（AGB）星编目，共包含45个目标，均以高角分辨率（约20毫角秒）的偏振光观测得到。本研究的主要目标是探测并表征近邻AGB星近邻环境中的尘埃壳层，同时借助安装在甚大望远镜（VLT）上的SPHERE仪器的苏黎世成像偏振仪（ZIMPOL），对获得的AGB星星周形态进行系统分类。我们提取并分析了45颗AGB星的偏振强度图，这些图由SPHERE/ZIMPOL仪器的偏振观测数据构建而成。我们采用椭圆拟合方法来表征星周包层，恒星参数（光度、有效温度、表面重力、消光、金属丰度）通过Python SED拟合工具（PySSED）软件进行光谱能量分布（SED）拟合汇编并在必要时重新计算。随后，这些数据被用于训练随机森林机器学习模型，以确定给定恒星周围已分辨包层的最具区分度的变量。我们为样本中的所有恒星构建了偏振图，揭示了星周形态的广泛多样性。我们探测到16个尘埃星周包层，其中包括3个从未被观测到的新包层，它们呈现出广泛的形态，均表现出明显的球对称性偏离，表明存在伴星相互作用或不对称质量抛射。随机森林模型确定了多个物理参数的最优阈值，从而提供了可靠的标准以预测SPHERE分辨AGB星周围尘埃包层的能力。这些结果有助于未来观测的目标选择，并为更好地理解星周包层的演化机制做出贡献。
英文摘要
We present the largest catalogue of asymptotic giant branch (AGB) stars, 45 targets in total, observed in polarized light at high angular resolution (~ 20 milliarcsec). The main goal of the study is to detect and characterize dust shells in the close environment of nearby AGB stars. This work also aims to systematically classify the AGB star circumstellar morphologies obtained with the SPHERE instrument installed at the Very Large Telescope (VLT), thanks to its Zurich Imaging Polarimeter (ZIMPOL). We extracted and analyzed polarized intensity maps for 45 AGB stars, constructed from polarimetric observation data obtained with the SPHERE/ZIMPOL instrument. An ellipse fitting method was applied to characterize the circumstellar envelopes. Stellar parameters (luminosity, effective temperature, surface gravity, extinction, metallicity) were compiled and recalculated when necessary from spectral energy distribution (SED) fitting using the Python SED fitting tool (PySSED) software. These data were then used to train a random forest machine learning model to determine the most discriminating variables for a resolved envelope around a given star. We constructed polarization maps for all stars in the sample, revealing a wide diversity of circumstellar morphologies. We detected 16 dusty circumstellar envelopes, including three never observed before. They display a wide range of morphologies, all of them showing a clear departure from spherical symmetry, indicating interaction with a companion or asymmetric mass ejections. The random forest model identified optimal thresholds for several physical parameters, thus providing robust criteria to anticipate SPHERE's ability to resolve dust envelopes around AGB stars. These results facilitate the selection of targets for future observations and contribute to a better understanding of the evolution mechanisms of circumstellar envelopes.
