We report about an ongoing photometric and spectroscopic monitoring survey of about 250 O- and 540 B-type stars in the southern Milky Way with the aim to determine the fraction of close binary systems as a function of mass and to determine the physical parameters of the individual components in the multiple systems. Preliminary results suggest that the multiplicity rate drops from 80% for the highest masses to 20% for stars of 3 solar masses. Our analysis indicates that the binary systems often contain close pairs with components of similar mass. This coincidence cannot originate from a random tidal capture in a dense cluster but is likely due to a particular formation process for high-mass stars. The large percentage of multiple systems requires a new photometric calibration for the absolute magnitudes of O-type stars.
It is now well established that the majority of massive stars reside in multiple systems. However, the effect of multiplicity is not sufficiently understood, resulting in a plethora of uncertainties about the end stages of massive-star evolution. In order to investigate these uncertainties, it is useful to study massive stars just before their demise. Classical Wolf-Rayet stars represent the final end stages of stars at the upper-mass end. The multiplicity fraction of these stars was reported to be ${\sim}0.4$ in the Galaxy but no correction for observational biases has been attempted. The aim…
We present the results of a multiplicity survey for a magnitude-limited sample of 31 classical Be stars conducted with the Navy Precision Optical Interferometer and the Mark III Stellar Interferometer. The interferometric observations were used to detect companions in ten previously known binary systems. For two of these sources (66 Oph and $β$ Cep) new orbital solutions were obtained, while for a third source ($\upsilon$ Sgr) our observations provide the first direct, visual detection of the hot sdO companion to the Be primary star. Combining our interferometric observations with an extensive…
We use the multi-epoch radial velocities acquired by the APOGEE survey to perform a large scale statistical study of stellar multiplicity for field stars in the Milky Way, spanning the evolutionary phases between the main sequence and the red clump. We show that the distribution of maximum radial velocity shifts (\drvm) for APOGEE targets is a strong function of \logg, with main sequence stars showing \drvm\ as high as $\sim$300 \kms, and steadily dropping down to $\sim$30 \kms\ for \logg$\sim$0, as stars climb up the Red Giant Branch (RGB). Red clump stars show a distribution of \drvm\ values…
The multiplicity of massive stars in the Orion Nebula cluster as seen with long-baseline interferometry
多恒星系统的表征是检验当前恒星形成模型的一个重要组成部分。恒星在多个星系中发现的频率越高，它们的质量越大。因此，完整地了解高质量恒星在整个轨道分离范围内的多样性对于理解它们仍然存在争议的形成过程至关重要。对猎户座星云团的观测有助于回答有关多恒星起源和演化的问题。早期的研究提供了一个很好的知识，在非常小的（光谱）和大的分离（AO，斑点）的恒星的多样性，从而使ONC这样一个项目的一个很好的目标。我们使用VLTI的近红外干涉仪AMBER观察ONC中的亮星样本。我们通过NACO对θ1 Ori A的观测档案来补充我们的数据集，以获得有关近距离可见伴星轨道的更多信息。我们的观测分辨了已知的多重系统θ1 Ori C和θ1 Ori A，并提供了新的轨道点，证实了θ1 Ori C的轨道预测和恒星参数测定。结合AMBER和NACO关于θ1 Ori A的数据，我们能够跟踪2003年至2011年的伴星运动。此外，我们还发现了θ1猎户座D周围的伴星和NU猎户座之前未知的伴星的线索。在约90%的概率下，我们可以排除在我们的样本恒星周围质量> 3 Msun的伴星，其分离度在约2质量和约110质量之间。我们的结论是，θ1 Ori A周围的伴星很可能与主星有物理上的联系。新发现的可能的同伴进一步增加了ONC的多样性。对于我们的两个O型和三个B型恒星的样本，我们发现每个主星平均有2.5个已知的伴星，这是低质量恒星的五…
Search for associations containing young stars (SACY). VI. Is multiplicity universal? Stellar multiplicity in the range 3-1000 au from adaptive-optics observations
Context: The influence of stellar multiplicity on planet formation is not yet well determined. Most planets are found using indirect detection methods via the small radial velocity or photometric variations of the primary star. These indirect detection methods are not sensitive to wide stellar companions. High-resolution imaging is thus needed to identify potential (sub)stellar companions to these stars. Aims: In this study we aim to determine the (sub)stellar multiplicity status of exoplanet host stars, that were not previously investigated for stellar multiplicity in the literature. For syst…
Context. The statistical properties of binary stars are clues for understanding their formation process. A radial velocity survey was carried on amongst nearby G-type stars and the results were published in 1991. Aims. The survey of radial velocity measurements was extended towards K-type stars. Methods. A sample of 261 K-type stars was observed with the spectrovelocimeter CORAVEL (COrrelation RAdial VELocities). Those stars with a variable radial velocity were detected on the basis of the P(chi^2) test. The orbital elements of the spectroscopic binaries were then derived. Results. The statist…
Preliminary results on the ongoing spectroscopic study of the six brightest Orion Trapezium stars is presented here. The main purpose of this work is to better understand the multiplicity and stability of each of these subsystems and the dynamical future of the group. So far the most interesting results reached are: 1) The orbit of the secondary star of the eclipsing Component A (V1016 Ori) is highly inclined with respect to the equatorial plane of its primary star. 2) The also eclipsing binary BM Ori (Trapezium Component B) does have a tertiary member with period about 3.5 years, as proposed …
Most observed stars are part of a multiple star system, but the formation of such systems and the role of environment and various physical processes is still poorly understood. We present a suite of radiation-magnetohydrodynamic simulations of star-forming molecular clouds from the STARFORGE project that include stellar feedback with varied initial surface density, magnetic fields, level of turbulence, metallicity, interstellar radiation field, simulation geometry and turbulent driving. In our fiducial cloud the raw simulation data reproduces the observed multiplicity fractions for Solar-type …
Context. The multiplicity of classical Cepheids (CCs) and RR Lyrae stars (RRLs) is still imperfectly known, particularly for RRLs. Aims. In order to complement the close-in short orbital period systems presented in Paper I, our aim is to detect the wide, spatially resolved companions of the targets of our reference samples of Galactic CCs and RRLs. Methods. Angularly resolved common proper motion pairs were detected using a simple progressive selection algorithm to separate the most probable candidate companions from the unrelated field stars. Results. We found 27 resolved, high probability gr…
Classical Cepheids (CCs) and RR Lyrae stars (RRLs) are important classes of variable stars used as standard candles to estimate galactic and extragalactic distances. Their multiplicity is imperfectly known, particularly for RRLs. Astoundingly, to date only one RRL has convincingly been demonstrated to be a binary, TU UMa, out of tens of thousands of known RRLs. Our aim is to detect the binary and multiple stars present in a sample of Milky Way CCs and RRLs. In the present article, we combine the Hipparcos and Gaia DR2 positions to determine the mean proper motion of the targets, and we search …
Our uncertainties about binary star systems (and triples and so on) limit our capabilities in literally every single one of the Thematic Areas identified for Astro2020. We need to understand the population statistics of stellar multiplicity and their variations with stellar type, chemistry, and dynamical environment: Correct interpretation of any exoplanet experiment depends on proper treatment of resolved and unresolved binaries; stellar multiplicity is a direct outcome of star and companion formation; the most precise constraints on stellar structure come from well-characterized binary syste…
European Southern Observatory（欧洲南方天文台）；Institute of Astronomy, KU Leuven（鲁汶大学天体物理研究所）；Leuven Gravity Institute, KU Leuven（鲁汶大学引力研究所）；Univ. Grenoble Alpes, CNRS, IPAG（格勒诺布尔阿尔卑斯大学，法国国家科学研究中心，IPAG）；Physics Department, Technion - Israel institute of Technology（以色列理工学院物理系）；Anton Pannekoek Institute, University of Amsterdam（阿姆斯特丹大学安东·潘内科克研究所）；School of Mathematics, Statistics and Physics, Newcastle University（纽卡斯尔大学数学、统计与物理学院）；Royal Observatory of Belgium（比利时皇家天文台）；ESO Headquarters（欧洲南方天文台总部）；German Aerospace Center (DLR)（德国航空航天中心）
Star cluster formation from turbulent clumps. V. Stellar clustering around massive stars
University of Virginia（弗吉尼亚大学）；Virginia Institute for Theoretical Astronomy, University of Virginia（弗吉尼亚理论天文学研究所，弗吉尼亚大学）；University of Texas at Austin（德克萨斯大学奥斯汀分校）；McMaster University（麦克马斯特大学）；Chalmers University of Technology（查尔姆斯理工大学）
The Multiplicity of Massive Stars: A High Angular Resolution Survey with the HST Fine Guidance Sensor
本文介绍了利用哈勃空间望远镜精制导敏感器在大质量恒星中搜寻角分辨双星系统的全天巡天观测结果。224颗恒星的样本主要由银河系的O型和B型恒星和亮蓝变星组成，加上大麦云星云中的一些亮星。FGS TRANS模式观测对角距在0。”01和1。“0并且比$\triangle m = 5$亮。FGS观测分辨了52个双星系统和6个三星系统，并在另外7个目标中探测到部分分辨的双星系统（其中43个是新探测到的）。对于FGS调查，这些数字产生29%的伴随检测频率。我们还收集了文献结果的数量密切的光谱双星和更广泛的天体测量双星之间的样本，我们提出了估计的频率的多个系统和伴侣频率的恒星的子集居住在集群和协会，场星，和失控的明星。这些结果证实了高的多重性分数，特别是在星团和星协中的大质量恒星之间。我们发现，周期分布是近似平坦的对数P的增量。我们确定了一些系统的长期轨道测定的潜在利益，我们注意到的重要性，这些同伴的解释的径向速度和光变曲线的密切的二进制有第三同伴。
Most massive stars reside in multiple systems that will interact over the course of their lifetime. Classical Wolf-Rayet (WR) stars represent the final end stages of stellar evolution at the upper-mass end. As part of a homogeneous, magnitude-limited ($V\leq12$) spectroscopic survey of northern Galactic WR stars, this paper aims to establish the observed and intrinsic multiplicity properties of the early-type nitrogen-rich WR population (WNE). We obtained high-resolution spectroscopic time series of the complete magnitude-limited sample of 16 WNE stars observable with the 1.2 m Mercator telesc…
We present observations of disc-bearing stars in Upper Scorpius (US) and Upper Centaurus-Lupus (UCL) with moderate resolution spectroscopy in order to determine the influence of multiplicity on disc persistence after ~5-20 Myr. Discs were identified using infra-red (IR) excess from the Wide-field Infra-red Survey Explorer (WISE) survey. Our survey consists of 55 US members and 28 UCL members, using spatial and kinematic information to assign a probability of membership. Spectra are gathered from the ANU 2.3m telescope using the Wide Field Spectrograph (WiFeS) to detect radial velocity variatio…
It is well known that massive O-stars are frequently (if not always) found in binary or higher-order multiple systems, but this fact has been less robustly investigated for the lower mass range of the massive stars, represented by the B-type stars. Obtaining the binary fraction and orbital parameter distributions of B-type stars is crucial to understand the impact of multiplicity on the archetypal progenitor of core-collapse supernovae as well as to properly investigate formation channels for gravitational wave progenitors. This work aims to characterise the multiplicity of the B-star populati…
OB stars powering stellar bowshock nebulae (SBNe) have been presumed to have large peculiar velocities. We measured peculiar velocities of SBN central stars to assess their kinematics relative to the general O star population using $Gaia$ EDR3 data for 267 SBN central stars and a sample of 455 Galactic O stars to derive projected velocities $v_{\rm 2D}$. For a subset of each sample we obtained new optical spectroscopy to measure radial velocities and identify multiple-star systems. We find a minimum multiplicity fraction of 36$\pm$6% among SBN central stars, consistent with $>$28% among runawa…
The majority of stars have one or more stellar companions. As exoplanets continue to be discovered, it is crucial to examine planetary systems to identify their stellar companions. By observing a change in proper motion, companions can be detected by the acceleration they induce on their host stars. We selected 701 stars from the Hipparcos-Gaia Catalog of Accelerations (HGCA) that have existing adaptive optics imaging data gathered with Gemini/NIRI. Of these, we examined 21 stars known to host planet candidates and reduced their archival NIRI data with Gemini's DRAGONS software. We assessed th…
