标题： 利用盖亚视差测量和CO5BOLD RHD模拟获取AGB恒星的恒星参数和动力学 显示英文标题

标题： Retrieving stellar parameters and dynamics of AGB stars with Gaia parallax measurements and CO5BOLD RHD simulations

摘要： 上下文。 渐近巨星分支（AGB）恒星的复杂动力学及其产生的恒星风对恒星参数的测量有显著影响，并放大了它们的不确定性。 三维（3D）辐射流体动力学（RHD）模拟显示，AGB恒星表面的对流相关结构会影响光中心位移和盖亚（Gaia）测量的视差不确定性。 目标。 我们探讨对流对光中心变化的影响，并旨在建立光中心位移与恒星参数之间的解析定律，以从视差不确定性中检索这些参数。 方法。 我们使用了31个CO5BOLD的RHD模拟以及后处理辐射转移代码Optim3D来计算盖亚G波段[320-1050 nm]中的强度图。 从这些图中，我们计算了光中心位置和时间波动。 然后我们将合成标准偏差与53颗米拉变星的视差不确定性进行了比较，这些米拉变星是用Gaia观测的。 结果。 模拟显示光中心在恒星表面的位移范围为对应恒星半径的4%到13%，这与之前的研究一致。 我们提供了一个解析定律，将模拟的脉动周期与光中心位移以及脉动周期与恒星参数相关联。 通过结合这些定律，我们检索了样本中恒星的表面重力、有效温度和半径。 结论。 我们的分析突出了一种使用最先进的AGB恒星对流三维数值模拟和AGB恒星视差观测来检索恒星参数的原创方法。 这将帮助我们进一步理解这些巨星。 显示英文摘要

摘要： Context. The complex dynamics of asymptotic giant branch (AGB) stars and the resulting stellar winds have a significant impact on the measurements of stellar parameters and amplify their uncertainties. Three-dimensional (3D) radiative hydrodynamic (RHD) simulations of convection suggest that convection-related structures at the surface of AGB star affect the photocentre displacement and the parallax uncertainty measured by Gaia. Aims. We explore the impact of the convection on the photocentre variability and aim to establish analytical laws between the photocentre displacement and stellar parameters to retrieve such parameters from the parallax uncertainty. Methods. We used a selection of 31 RHD simulations with CO5BOLD and the post-processing radiative transfer code Optim3D to compute intensity maps in the Gaia G band [320-1050 nm]. From these maps, we calculated the photocentre position and temporal fluctuations. We then compared the synthetic standard deviation to the parallax uncertainty of a sample of 53 Mira stars observed with Gaia. Results. The simulations show a displacement of the photocentre across the surface ranging from 4 to 13 % of the corresponding stellar radius, in agreement with previous studies. We provide an analytical law relating the pulsation period of the simulations and the photocentre displacement as well as the pulsation period and stellar parameters. By combining these laws, we retrieve the surface gravity, the effective temperature, and the radius for the stars in our sample. Conclusions. Our analysis highlights an original procedure to retrieve stellar parameters by using both state-of-the-art 3D numerical simulations of AGB stellar convection and parallax observations of AGB stars. This will help us refine our understanding of these giants.