Radio astrometry of nearby, low-mass stars has the potential to be a powerful tool for the discovery and characterization of planetary companions. We present a Very Large Array survey of 172 active M dwarfs at distances of less than 10 pc. Twenty nine stars were detected with flux densities greater than 100 microJy. We observed 7 of these stars with the Very Long Baseline Array at milliarcsecond resolution in three separate epochs. With a detection threshold of 500 microJy in images of sensitivity 1 sigma ~ 100 microJy, we detected three stars three times (GJ 65B, GJ896A, GJ 4247), one star twice (GJ 285), and one star once (GJ 803). Two stars were undetected (GJ 412B and GJ 1224). For the four stars detected in multiple epochs, residuals from the optically-determined proper motions have an rms deviation of ~0.2 milliarcseconds, consistent with statistical noise limits. Combined with previous optical astrometry, these residuals provide acceleration upper limits that allow us to exclude planetary companions more massive than 3-6 M_Jup at a distance of ~1 AU with a 99% confidence level.
With Hubble Space Telescope Fine Guidance Sensor astrometry and published and previously unpublished radial velocity measures we explore the exoplanetary system mu Arae. Our modeling of the radial velocities results in improved orbital elements for the four previously known components. Our astrometry contains no evidence for any known companion, but provides upper limits for three companion masses. A final summary of all past Fine Guidance Sensor exoplanet astrometry results uncover a bias towards small inclinations (more face-on than edge-on). This bias remains unexplained by either small num…
High Definition Astrometry (0.1 - 1.0 micro-arcseconds) will open a new window into neighboring planetary systems. For the first time, the realm of temperate terrestrial worlds will be explored. This includes Earth Analogs, thereby allowing the value of eta-Earth to be directly determined, without resort to extrapolation. High Definition Astrometry will provide a means to confirm the existence of Radial Velocity (RV) planets while, at the same time, measuring true mass, along with orbit inclination and radius, i.e., system architecture. Planetary systems not amenable to RV search, such as thos…
Precision Astrometry of a Sample of Speckle Binaries and Multiples with the Adaptive Optics Facilities at the Hale and Keck II Telescopes
我们使用200英寸Hale和10 m Keck II的自适应光学设施，在近红外波段观察到了12颗联星和多星以及一个疏散星团的样本。我们使用这些系统的近衍射极限图像来测量它们的组件之间的相对间距和位置角。本文研究了差色折射和碎片畸变对相对天体测量的影响，并进行了修正。在一个晚上，我们实现了天体测量精度通常远低于1毫弧秒，偶尔小到40微弧秒。这样的精度原则上足以对附近双星和多星组成部分周围的行星质量天体进行天体测量。由于我们还没有足够大的数据集的恒星观测样本来检测行星，我们提供了行星质量的天体的基础上获得的天体测量精度的限制。
We present constraints on the presence of substellar companions to the nearby ($d\sim7.6$ pc), young ($440\pm40$ Myr) K4Ve star TW Piscis Austrini, the wide ($\sim$0.3 pc) companion to the A4V star Fomalhaut. We combined absolute astrometry from Hipparcos and Gaia with literature radial velocity measurements and dedicated high-contrast imaging observations obtained with Keck/NIRC2 to achieve sensitivity to brown dwarf and planetary-mass companions ($\gtrsim2$ M$_{\rm Jup}$) over many decades of orbital period ($\lesssim 10^3$ yr). The significant astrometric acceleration measured between the H…
Context. Thanks to more than 20 years of monitoring, the radial velocity (RV) method has detected long-period companions (P > 10yr) around several dozens of stars. Yet, the true nature of these companions remains unclear because of the uncertainty as to the inclination of the companion orbital plane. Aims. We wish to constrain the orbital inclination and the true mass of long-period single companions. Methods. We used a Markov Chain Monte Carlo (MCMC) fitting algorithm to combine RV measurements with absolute astrometry and, when available, relative astrometry data. Results. We have lifted the…
Stellar activity strongly affects and may prevent the detection of Earth-mass planets in the habitable zone of solar-type stars with radial velocity technics. Astrometry is in principle less sensitive to stellar activity because the situation is more favourable: the stellar astrometric signal is expected to be fainter than the planetary astrometric signal compared to radial velocities. We quantify the effect of stellar activity on high-precision astrometry when Earth-mass planets are searched for in the habitable zone around old main-sequence solar-type stars. We used a very large set of magne…
GJ676A is an M0 dwarf hosting both gas-giant and super-Earth-type planets discovered with radial-velocity measurements. Using FORS2/VLT, we obtained position measurements of the star in the plane of the sky that tightly constrain its astrometric reflex motion caused by the super-Jupiter planet `b` in a 1052-day orbit. This allows us to determine the mass of this planet to $M_\mathrm{b} = 6.7^{+1.8}_{-1.5}\,M_\mathrm{J}$, which is $\sim$40 \% higher than the minimum mass inferred from the radial-velocity orbit. Using new HARPS radial-velocity measurements, we improve upon the orbital parameters…
Revisiting Planetary Systems in Okayama Planet Search Program: A new long-period planet, RV astrometry joint analysis, and multiplicity-metallicity trend around evolved stars
Closeby Habitable Exoplanet Survey (CHES). V. Planetary Parameters Derived from Angular Separation Variations
University of Science and Technology of China（中国科学技术大学）；CAS Center for Excellence in Comparative Planetology（中国科学院比较行星学卓越创新中心）；University of Chinese Academy of Sciences（中国科学院大学）；University of Exeter（埃克塞特大学）；China National Laboratory on Adaptive Optics（自适应光学国家实验室）；Institute of Optics and Electronics, Chinese Academy of Sciences（中国科学院光电技术研究所）
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。
AB Aur, a Rosetta stone for studies of planet formation (IV): C/O estimates from CS and SO interferometric observations
Observatorio Astronómico Nacional (OAN,IGN)（国家天文台）；Centro de Astrobiología (CAB), INTA-CSIC（天体生物学中心）；Institut de Radioastronomie Millimétrique（毫米波射电天文学研究所）；Institut de Planétologie et d’Astrophysique de Grenoble (IPAG), Université Grenoble Alpes, CNRS（格勒诺布尔行星学与天体物理学研究所）；Max-Planck-Institut für Astronomie (MPIA)（马克斯·普朗克天文学研究所）；Ludwig-Maximilians-Universität（路德维希-马克西米利安大学）；Massachusetts Institute of Technology（麻省理工学院）
High precision astrometry mission for the detection and characterization of nearby habitable planetary systems with the Nearby Earth Astrometric Telescope (NEAT)
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）
We developed and provide AnalyticLC, a novel analytic method and code implementation for dynamical modeling of planetary systems, including non-coplanar interactions, based on a disturbing function expansion to fourth order in eccentricities and inclinations. AnalyticLC calculates the system dynamics in 3D and the resulting model light curve, radial velocity, and astrometry signatures, enabling simultaneous fitting of these data. We show that for a near-resonant chain of three planets, where the two super-periods are close to each other, the TTVs of the pair-wise interactions cannot be directl…
Detailed study of HD 219134: a benchmark K-dwarf with a compact planetary system
Universität Zürich（苏黎世大学）；Uppsala University（乌普萨拉大学）；INAF-IAPS（意大利国家天体物理研究所-空间天体物理研究所）；University of Liège（列日大学）；Leiden University（莱顿大学）；University of Tartu（塔尔图大学）
We present multi-epoch astrometric radio observations with the Very Long Baseline Array (VLBA) of the young ultracool-dwarf binary LSPM J1314+1320AB . The radio emission comes from the secondary star. Combining the VLBA data with Keck near-infrared adaptive-optics observations of both components, a full astrometric fit of parallax ($π_{\rm abs}=57.975\pm0.045$ mas, corresponding to a distance of $d=17.249\pm0.013$ pc), proper motion ($μ_{\rm αcos δ}=-247.99\pm0.10$ mas yr$^{-1}$, $μ_δ=-183.58\pm0.22$ mas yr$^{-1}$), and orbital motion is obtained. Despite the fact that the two components have …
Interferometric Detection and Orbit Modeling of the Subcomponent in the Hot-dust System $κ$ Tuc A: A Low-mass Star on an Eccentric Orbit in a Hierarchical-quintuple System
The formation of giant planets is best studied through direct imaging by observing planets both during and after formation. Giant planets are expected to form either by core accretion, which is typically associated with low initial entropy (cold-start models) or by gravitational instability, which corresponds to a high initial entropy of the gas (hot-start models). Thus, constraining the initial entropy provides insight into the planet formation mechanism and determines the resultant brightness evolution. We find that, by observing planets in nearby moving groups of known age both through dire…
Occultations of stars by asteroids have been observed since 1961, increasing from a very small number to now over 500 annually. We have created and regularly maintain a growing data-set of more than 5,000 observed asteroidal occultations. The data-set includes: the raw observations; astrometry at the 1 mas level based on centre of mass or figure (not illumination); where possible the asteroid's diameter to 5 km or better, and fits to shape models; the separation and diameters of asteroidal satellites; and double star discoveries with typical separations being in the tens of mas or less. The da…
The compact mm-wavelength signal in the central cavity of the PDS70 disc, revealed by deep ALMA observations, is aligned with unresolved Halpha emission, and is thought to stem from a circum-planetary disc (CPD) around PDS70c. We revisit the available ALMA data on PDS70c with alternative imaging strategies, and with special attention to uncertainties and to the impact of the so-called "JvM correction", which is thought to improve the dynamic range of restored images. We also propose a procedure for the alignment and joint imaging of multi-epoch visibility data. We find that the JvM correction …
Young planets provide a window into the early stages and evolution of planetary systems. Ideal planets for such research are in coeval associations, where the parent population can precisely determine their ages. We describe a young association (MELANGE-3) in the Kepler field, which harbors two transiting planetary systems (Kepler-1928 and Kepler-970). We identify MELANGE-3 by searching for kinematic and spatial overdensities around Kepler planet hosts with high levels of lithium. To determine the age and membership of MELANGE-3, we combine new high-resolution spectra with archival light curve…
Transiting Planetary Systems with Distant Giant Companions Remain Moderately Coplanar
State Key Laboratory of Dark Matter Physics, Tsung-Dao Lee Institute & School of Physics and Astronomy, Shanghai Jiao Tong University（暗物质物理国家重点实验室，李政道理论与计算科学中心及物理与天文学院，上海交通大学）；CAS Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences（中国科学院光学天文重点实验室，国家天文台，中国科学院）；Institute for Astronomy, University of Hawai‘i（夏威夷大学天体物理研究所）
The NASA K2 mission uses photometry to find planets transiting stars of various types. M dwarfs are of high interest since they host more short period planets than any other type of main sequence stars and transiting planets around M dwarfs have deeper transits compared to other main sequence stars. In this paper, we present stellar parameters from K and M dwarfs hosting transiting planet candidates discovered by our team. Using the SOFI spectrograph on the European Southern Observatory's New Technology Telescope, we obtained R ~ 1000 J-, H-, and K-band (0.95 - 2.52 microns) spectra of 34 late…
The orbits of binary stars and planets, particularly eccentricities and inclinations, encode the angular momentum within these systems. Within stellar multiple systems, the magnitude and (mis)alignment of angular momentum vectors among stars, disks, and planets probes the complex dynamical processes guiding their formation and evolution. The accuracy of the \textit{Gaia} catalog can be exploited to enable comparison of binary orbits with known planet or disk inclinations without costly long-term astrometric campaigns. We show that \textit{Gaia} astrometry can place meaningful limits on orbital…
