We present an analysis of the potential follow-up polarimetry microlensing observation to study the stellar atmospheres of the distant stars. First, we produce synthetic microlensing events using the Galactic model, stellar population, and interstellar dust toward the Galactic Bulge. We simulate the polarization microlensing light curves and pass them through the instrument specifications of FOcal Reducer and low dispersion Spectrograph (FORS2) polarimeter at Very Large Telescope (VLT), and then analyze them. We find that the accuracy of the VLT telescope lets us constrain the atmosphere of cool RGB stars. Assuming detection of about $3000$ microlensing events per year by the OGLE telescope, we expect to detect almost $20,~10,~8, $ and $5$ of polarization microlensig events for the four different criteria of being three consecutive polarimetry data points above the baseline with $1\sigma$, $2\sigma$, $3\sigma$, and $4\sigma$, respectively in the polarimetry light curves. We generalize the covariance matrix formulation and present the combination of polarimetry and photometry information that leads us to measure the scattering optical depth of the atmosphere and the inner radius of the stellar envelope of red giant stars. These two parameters could determine the dust opacity of the atmosphere of cool RGB source stars and the radius where dust can be formed.

中文翻译：

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使用后续偏振微透镜观测测量恒星大气参数

我们对潜在的后续偏振微透镜观测进行了分析，以研究遥远恒星的恒星大气。首先，我们使用银河模型、恒星种群和星际尘埃向银河凸起产生合成微透镜事件。我们模拟偏振微透镜光曲线，并通过甚大望远镜（VLT）的焦距衰减器和低色散光谱仪（FORS2）偏振计的仪器规格，然后对其进行分析。我们发现 VLT 望远镜的精度让我们可以限制冷 RGB 恒星的大气。假设 OGLE 望远镜每年检测到大约 3000 美元的微透镜事件，我们预计将检测到近 20、~10、~8 美元，$ 和 $5$ 的偏振微透镜事件的四个不同标准，即在基线上方的三个连续偏振数据点，分别在偏振光中具有 $1\sigma$、$2\sigma$、$3\sigma$ 和 $4\sigma$曲线。我们概括了协方差矩阵公式，并提出了偏振测量和光度测量信息的组合，使我们能够测量大气的散射光学深度和红巨星的恒星包层的内半径。这两个参数可以决定冷RGB源星大气的尘埃不透明度和尘埃形成的半径。我们概括了协方差矩阵公式，并提出了偏振测量和光度测量信息的组合，使我们能够测量大气的散射光学深度和红巨星的恒星包层的内半径。这两个参数可以决定冷RGB源星大气的尘埃不透明度和尘埃形成的半径。我们概括了协方差矩阵公式，并提出了偏振测量和光度测量信息的组合，使我们能够测量大气的散射光学深度和红巨星的恒星包层的内半径。这两个参数可以决定冷RGB源星大气的尘埃不透明度和尘埃形成的半径。