The ESA global astrometry space mission Gaia has been monitoring the position of a billion stars since 2014. The analysis of such a massive dataset is challenging in terms of the data processing involved. In particular, the blind detection and characterization of single or multiple companions to stars (planets, brown dwarfs, or stars) using Gaia astrometry requires highly efficient algorithms. In this article, we present a set of analytical methods to detect and characterize companions in scanning space astrometric time series as well as via a combination of astrometric and radial velocity time series. We propose a general linear periodogram framework and we derive analytical formulas for the false alarm probability (FAP) of periodogram peaks. Once a significant peak has been identified, we provide analytical estimates of all the orbital elements of the companion based on the Fourier decomposition of the signal. The periodogram, FAP, and orbital elements estimates can be computed for the astrometric and radial velocity time series separately or in tandem. These methods are complementary with more accurate and more computationally intensive numerical algorithms (e.g., least-squares minimization, Markov chain Monte Carlo, genetic algorithms). In particular, our analytical approximations can be used as an initial condition to accelerate the convergence of numerical algorithms. Our formalism has been partially implemented in the Gaia exoplanet pipeline for the third Gaia data release. Since the Gaia astrometric time series are not yet publicly available, we illustrate our methods on the basis of Hipparcos data, together with on-ground CORALIE radial velocities, for three targets known to host a companion: HD 223636 (HIP 117622), HD 17289 (HIP 12726), and HD 3277 (HIP 2790).
Predicting Gaia astrometry's ability to constrain the populations of circumbinary planets
School of Physics and Astronomy, University of Birmingham（伯明翰大学物理与天文学学院）；Tsung-Dao Lee Institute, Shanghai Jiao Tong University（上海交大李政道研究所）；European Space Agency (ESA), European Space Astronomy Centre (ESAC)（欧洲空间局（ESA），欧洲空间天文中心（ESAC））
Bayesian analysis of Gaia epoch astrometry and radial velocities with kima
Tsung-Dao Lee Institute, Shanghai Jiao Tong University（上海交大李政道研究所）；School of Physics and Astronomy, University of Birmingham（伯明翰大学物理与天文学院）；Observatoire Astronomique de l’Université de Genève（日内瓦大学天文台）
A pilot study on the CSST astrometric capability: Detecting astrometric binaries with Gaia synergy via simulated data
Shanghai Astronomical Observatory, Chinese Academy of Sciences（中国科学院上海天文台）；School of Astronomy and Space Sciences, University of Chinese Academy of Sciences（中国科学院大学天文与空间科学学院）
True Masses using RV data with Hipparcos and Gaia Astrometry
INAF – Osservatorio Astronomico di Palermo（意大利国家天体物理研究所巴勒莫天文台）；Dipartimento di Fisica e Chimica, Università degli Studi di Palermo（巴勒莫大学物理与化学系）；INAF – Osservatorio Astrofisico di Torino（意大利国家天体物理研究所都灵天文台）；Dipartimento di Fisica, Università degli Studi di Torino（都灵大学物理系）
Precise dynamical masses of new directly imaged companions from combining relative astrometry, radial velocities, and Hipparcos-Gaia eDR3 accelerations
Mass-dependent multiplicity fraction in low mass stars revealed by Gaia astrometry
Max-Planck-Institut für Astronomie（马克斯·普朗克天文学研究所）；Fakultät für Physik und Astronomie, Universität Heidelberg（海德堡大学物理与天文学院）；Department of Astronomy, California Institute of Technology（加州理工学院天文学系）
New evidence about HW Vir's circumbinary planets from Hipparcos-Gaia astrometry and a reanalysis of the eclipse timing variations using nested sampling
本研究结合 Hipparcos-Gaia 自行异常与 kima 嵌套采样重新分析 HW Vir 食掩时刻，约束伴星质量并指出四信号中仅最外侧信号可能为行星。
New members of the Lupus I cloud based on Gaia astrometry Physical and accretion properties from X-Shooter spectra
我们表征12个年轻的恒星物体（YSO）位于狼疮I区域，空间上重叠的上半人马座狼疮（UCL）的亚恒星协会。本研究的目的是了解是否狼疮I云有更多的成员比已经声称到目前为止在文献中，并获得更深入的了解该地区的全球属性。我们使用盖亚DR 2目录选择了我们的目标，基于它们与狼疮I真正成员一致的运动学特性。在X射手观察到的12个YSO样本中，我们确定了10个狼疮I成员。由于技术问题，我们无法确定两个目标的成员状态，即Gaia DR 2 6014269268967059840和2 MASS J15361110-3444473。我们发现我们的四个目标是吸积体，其中2 MASS J15551027-3455045，质量约为0.03 M_Sun，是迄今为止狼疮复合体中质量最小的吸积体之一。我们的几个目标（包括吸积体）是相对于狼疮I的主灯丝在原位和离云形成的，因此，我们的研究可能暗示在狼疮I主灯丝周围有扩散的M-矮星种群。在这种情况下，我们想强调的是，我们与盖亚目录的运动学分析在识别狼疮I云的新成员方面发挥了关键作用。
The GAPS programme at TNG LXX. HD 128717 B/Gaia-6 B: a long-period eccentric low-mass brown dwarf from astrometry and radial velocities
INAF - Osservatorio Astronomico di Padova（意大利国家天体物理研究所帕多瓦天文台）；INAF - Osservatorio Astronomico di Roma（意大利国家天体物理研究所罗马天文台）；INAF - Osservatorio Astrofisico di Catania（意大利国家天体物理研究所卡塔尼亚天文台）；INAF - Osservatorio Astronomico di Palermo（意大利国家天体物理研究所巴勒莫天文台）；Department of Astronomy and Steward Observatory, The University of Arizona（亚利桑那大学天文学系和斯图尔德天文台）；Fundación Galileo Galilei - INAF（伽利略基金会-意大利国家天体物理研究所）；School of Earth and Space Exploration, Arizona State University（亚利桑那州立大学地球与空间探索学院）；Department of Physics, University of Turin（都灵大学物理系）；INAF - Osservatorio Astronomico di Brera（意大利国家天体物理研究所布雷拉天文台）
A Planetary Illusion's Funeral: Non-detection of a Gaia DR3 Exoplanet Candidate, and the Role of Intermediate-precision Radial Velocities in Gaia Exoplanet Follow-up
Centre for Astrophysics, University of Southern Queensland（南昆士兰大学天体物理中心）；Max Planck Institute for Astronomy（马克斯·普朗克天文学研究所）；Center for Astrophysics, Harvard & Smithsonian（哈佛-史密森尼天体物理中心）
Constraining the Orbit and Mass of epsilon Eridani b with Radial Velocities, Hipparcos IAD-Gaia DR2 Astrometry, and Multi-epoch Vortex Coronagraphy Upper Limits
The Possible Astrometric Signature of a Planetary-mass Companion to the Nearby Young Star TW Piscis Austrini (Fomalhaut B): Constraints from Astrometry, Radial Velocities, and Direct Imaging
我们目前的限制存在的亚恒星同伴附近（$d\sim7.6$ pc），年轻的（$440\pm40$百万年）K4 Ve星TW双鱼座Australini，宽（$\sim$ 0.3 pc）同伴A4 V星北落师门。我们将依巴谷和盖亚的绝对天体测量与文献径向速度测量和Keck/NIRC 2获得的专用高对比度成像观测相结合，以实现对数十年轨道周期（$\lesssim 10^3$ yr）的棕矮星和行星质量伴星（$\gtrsim2$ M $_{\rm Jup}$）的灵敏度。在依巴谷星表和盖亚星表之间测得的显著天体测量加速度，以前在文献中报道过，不能用TW PsA围绕北落师门三重系统重心的轨道运动来解释。相反，我们发现它是一致的反射运动引起的轨道亚恒星的同伴。天体测量、径向速度和深$L^{\prime}$成像数据集的组合导致对$1.2_{-0.6}^{+0.7}$ M $_{\rm Jup}$的伴星质量的限制。然而，伴星的周期受到很差的约束，由于依巴谷和盖亚之间的24.25年基线混叠，因此具有高度多模态的周期后验分布。如果通过持续的天体测量或光谱监测，或通过直接探测得到证实，TW PsA的伴星将成为即将到来的詹姆斯韦伯太空望远镜和宽视场红外巡天望远镜上使用高对比度仪器进行详细大气特征描述的首选目标。
