发表机构
KU Leuven; Observatoire de Paris, Université PSL, Sorbonne Université, Université Paris Cité, CY Cergy Paris Université, CNRS; French-Chilean Laboratory for Astronomy, IRL 3386, CNRS and U. de Chile（荷语鲁汶大学; 巴黎天文台，巴黎文理研究大学，索邦大学，巴黎西岱大学，塞吉-蓬图瓦兹大学，法国国家科学研究中心; 法智利天文学联合实验室，法国国家科学研究中心和智利大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究扩展了未分辨演化双星的天体测量模型，结合开普勒光心运动等，测试纳入红噪声协方差矩阵的检索框架，可从盖亚历元天体测量恢复近距未分辨 AGB 双星的可靠轨道与天体测量参数。
AI 中文摘要
对内禀变星的高精度天体测量的解释仍具挑战性，尤其是包含渐近巨星支（AGB）星的未分辨双星系统。这类系统中，大振幅脉动与演化的对流表面结构会引发时变的光心位移，从而扰动观测到的轨道运动。与此同时，盖亚 DR4 历元天体测量为近距未分辨 AGB 双星推导精确的轨道解与三角视差提供了可能。基于变光诱导运动体（VIM）框架，我们通过结合开普勒光心运动、脉动诱导的流量依赖型光心位移以及对流诱导的光心运动，扩展了未分辨演化双星的天体测量模型。在正向模拟中，对流要么由从指数相关函数抽取的随机光心位移表示，要么由从三维辐射流体动力学模拟提取的光心时间序列表示。随后，我们测试了一种检索框架，该框架在拟合轨道与 VIM 信号的同时，纳入红噪声协方差矩阵以解释由对流产生的相关天体测量残差。我们表明，尽管存在强脉动与对流诱导的光心变异性，盖亚历元天体测量仍可恢复未分辨 AGB 双星的可靠轨道与天体测量参数。脉动诱导的变异性会产生可与开普勒光心轨道联合建模的相干 VIM 信号，而对流诱导的光心运动主要表现为时间相关的天体测量噪声。忽略该相关分量的检索会导致自行与三角视差出现偏差，而纳入基于物理的红噪声协方差模型则可准确恢复基础轨道解与天体测量参数。
英文摘要
(Abbreviated) The interpretation of high-precision astrometry for intrinsically variable stars remains challenging, particularly for unresolved binary systems containing asymptotic giant branch (AGB) stars. In such systems, large-amplitude pulsations and evolving convective surface structures induce time-dependent photocentre displacements that perturb the observed orbital motion. At the same time, Gaia DR4 epoch astrometry offers the prospect of deriving accurate orbital solutions and parallaxes for nearby unresolved AGB binaries. Building upon the variability-induced mover (VIM) framework, we extend the astrometric model for unresolved evolved binaries by combining Keplerian photocentre motion, pulsation-induced flux-dependent photocentre shifts, and convection-induced photocentre motion. In the forward simulations, convection is represented either by stochastic photocentre displacements drawn from an exponential correlation function or by photocentre time series extracted from 3D radiation-hydrodynamic simulations. We then test a retrieval framework that fits the orbital and VIM signal while incorporating a red-noise covariance matrix to account for correlated astrometric residuals produced by convection. We show that Gaia epoch astrometry can recover reliable orbital and astrometric parameters for unresolved AGB binaries despite strong pulsation- and convection-induced photocentre variability. Pulsation-induced variability produces a coherent VIM signal that can be modeled jointly with the Keplerian photocentre orbit, while convection-induced photocentre motion behaves primarily as temporally correlated astrometric noise. Retrievals that ignore this correlated component lead to biased proper motions and parallaxes, whereas the inclusion of a physically motivated red-noise covariance model enables accurate recovery of the underlying orbital solution and astrometric parameters.
Comments15 pages, 6 figures, accepted for publication by Astronomy & Astrophysics
