The identification of binary stars of different mass ratios in resolved stellar populations is a challenging task. We show how the photometric diagram constructed with the pseudo-colors (H-W2)-W1 vs W2-(BP-K) can be employed to estimate the binary and multiple star ratios and the distribution of their component mass ratio $q$ effectively. As an application, we investigate the Pleiades star cluster in the range of primary component mass between 0.5 and 1.8 $M_{\odot}$. The binary star ratio is found to be between 0.54$\pm$0.11 and 0.70$\pm$0.14. On the other hand, the ratio of systems with multiplicity more than 2 is between 0.10$\pm$0.00 and 0.14$\pm$0.01. The distribution of the component mass ratio $q$ has been approximated by a power law with the exponent between -0.53$\pm$0.10 and -0.63$\pm$0.22. Below 0.5 $M_{\odot}$, we expect a large number of brown dwarfs among secondary components.
In this study, we continue our project to search for unresolved binary and multiple systems in open clusters exploiting the photometric diagram (H-W2)-W1 vs W2-(BP-K) firstly introduced in \citet{Malofeeva+2022}. In particular, here we estimate the binary and multiple star ratios and the distribution of the component mass ratio $q$ in the Galactic clusters Alpha Persei, Praesepe, and NGC 1039. We have modified the procedure outlined in our first study \citep{Malofeeva+2022} making star counts automatic and by introducing bootstrapping for error estimation. Basing on this, we re-investigated th…
School of Physics and Astronomy, Sun Yat-sen University（中山大学物理学院）；CSST Science Center for the Guangdong-Hong Kong-Macau Greater Bay Area（粤港澳大湾区嫦娥工程科学中心）；Centre for Astrophysics, University of Southern Queensland（南昆士兰大学天体物理中心）
We present the results of a spectroscopic monitoring program of the Pleiades region aimed at completing the census of spectroscopic binaries in the cluster, extending it to longer periods than previously reachable. We gathered 6104 spectra of 377 stars between 1981 and 2021, and merged our radial velocities with 1151 measurements from an independent survey by others started three years earlier. With the combined data spanning more than 43 yr we have determined orbits for some 30 new binary and multiple systems, more than doubling the number previously known in the Pleiades. The longest period …
Radial-velocities for the early-type stars in the Pleiades cluster have always been challenging to measure because of the significant rotational broadening of the spectral lines. The large scatter in published velocities has led to claims that many are spectroscopic binaries, and in several cases preliminary orbital solutions have been proposed. To investigate these claims, we obtained and report here velocity measurements for 33 rapidly-rotating B, A, and early F stars in the Pleiades region, improving significantly on the precision of the historical velocities for most objects. With one or t…
The binary properties of open clusters place crucial constraints on star formation theory and clusters' dynamical evolution. We develop a comprehensive approach that models the color-magnitude diagram (CMD) of the cluster members as the mixture of single stars and photometric unresolved binaries. This method enables us to infer the binary properties, including the binary fraction $f_\mathrm{b}$ and binary mass-ratio distribution index $γ_q$ when a power-law is assumed, with high accuracy and precision, which were unfeasible in conventional methods. We employ a modified Gaussian process to dete…
21,864 Unresolved, Low-mass Binaries Identified via their Overluminosity in \textit{Gaia} DR3 and a Catalog of 347,440 Systems within 100 pc of the Sun
Georgia State University（佐治亚州立大学）；Planétarium de Montréal, Espace pour la Vie（蒙特利尔天文馆，生命空间）；Trottier Institute for Research on Exoplanets, Université de Montréal（特罗蒂尔系外行星研究所，蒙特利尔大学）；Vanderbilt University（范德堡大学）
Binary stars are present in all stellar systems, yet their role is far from being fully understood. We investigate the effect of unresolved binaries in the derivation of open clusters' mass by star counts. We start from the luminosity functions of five open clusters: IC 2714, NGC 1912, NGC 2099, NGC 6834 and NGC 7142. Luminosity functions are obtained via star counts extracted from the 2MASS database. The fraction of binaries is considered to be independent on stellar magnitude. We take into account different assumptions for the binary mass ratio distribution and assign binary masses using the…
Rotation periods obtained with the Kepler satellite have been combined with precise measurements of projected rotation velocity from the WIYN 3.5-m telescope to determine the distribution of projected radii for several hundred low-mass ($0.1 \leq M/M_{\odot} \leq 0.8$), fast-rotating members of the Pleiades cluster. A maximum likelihood modelling technique, that takes account of observational uncertainties, selection effects and censored data, and considers the effects of differential rotation and unresolved binarity, has been used to find that the average radius of these stars is $14 \pm 2$ p…
This note describes an effort to detect additional stellar sources in known transiting exoplanet (TEP) systems, which are unresolved or barely resolved in the Gaia Data Release 2 (DR2) catalogue. The presence of multiple unresolved stars in photometric and spectroscopic observations of a transiting planetary system biases measurements of the planet's radius, mass, and atmospheric conditions. In addition to the effect on individual planetary systems, the presence of unresolved stars across the sample of known exoplanets biases our overall understanding of planetary systems, due to the systemati…
We measure starspot filling fractions for 240 stars in the Pleiades and M67 open star clusters using APOGEE high-resolution H-band spectra. For this work we developed a modified spectroscopic pipeline which solves for starspot filling fraction and starspot temperature contrast. We exclude binary stars, finding that the large majority of binaries in these clusters (80%) can be identified from Gaia DR3 and APOGEE criteria -- important for field star applications. Our data agree well with independent activity proxies, indicating that this technique recovers real starspot signals. In the Pleiades,…
We use the data provided by the Gaia Early Data Release 3 to search for a highly-complete volume-limited sample of unresolved binaries consisting of a white dwarf and a main sequence companion (i.e. WDMS binaries) within 100pc. We select 112 objects based on their location within the Hertzsprung-Russell diagram, of which 97 are new identifications. We fit their spectral energy distributions (SED) with a two-body fitting algorithm implemented in VOSA (Virtual Observatory SED Analyser) to derive the effective temperatures, luminosities and radii (hence surface gravities and masses) of both compo…
For stars with unresolved companions, motions of the centre of light and that of mass decouple, causing a single-source astrometric model to perform poorly. We show that such stars can be easily detected with the reduced chi2 statistic, or RUWE, provided as part of Gaia DR2. We convert RUWE into the amplitude of the image centroid wobble, which, if scaled by the source distance, is proportional to the physical separation between companions (for periods up to several years). We test this idea on a sample of known spectroscopic binaries and demonstrate that the amplitude of the centroid perturba…
The population statistics of binary stars are an important output of star formation models. However populations of wide binaries evolve over time due to interactions within a system's birth environment and the unfolding of wide, hierarchical triple systems. Hence the wide binary populations observed in star forming regions or OB associations may not accurately reflect the wide binary populations that will eventually reach the field. We use Gaia DR2 data to select members of three open clusters, Alpha~Per, the Pleiades and Praesepe and to flag cluster members that are likely unresolved binaries…
A Cross-Match of 2MASS and SDSS. II. Peculiar L Dwarfs, Unresolved Binaries, and the Space Density of T Dwarf Secondaries
我们提出了一个程序的完成，以交叉相关的SDSS数据发布1和2MASS点源目录中寻找极红的L和T矮星。该计划由Metchev和合作者发起，他们提出了SDSS DR 1中所有新发现的T矮星的发现，并估计了太阳附近孤立的T0-T8矮星的空间密度。在目前的工作中，我们提出了大部分的L矮星的发现。我们的红敏感（z-J> 2.75等）交叉匹配被证明是有效的，在检测特殊的红色L型矮星，增加了两个新的，包括一个最红的已知L型矮星。我们的搜索还发现了一颗新的蓝色L7矮星，令人惊讶的是，还有两颗M8矮星。我们进一步扩大我们的分析，以检测未解决的二进制L或T矮星通过光谱模板拟合所有L和T矮星在这里和Metchev和合作者的早期工作。我们确定了九个可能的双星，其中六个是新的和八个港口可能T矮星secondaries。我们将这个结果与目前对亚恒星伴星的质量比分布和频率的了解相结合，估计出单个T0-T8矮星的总空间密度为0.005 - 0.05 pc ^{-3}。
Identification of unresolved binaries in the VVV b294 tile: A Pro-Am collaboration using the Virtual Observatory
Universidad Complutense de Madrid（马德里康普顿斯大学）；Centro de Astrobiología (CSIC-INTA)（天体生物学中心（西班牙国家研究委员会-国家航空航天技术研究所））；Asociación Astronómica AstroHenares（AstroHenares天文协会）；Agrupación Astronómica de Córdoba（科尔多瓦天文团）；Agrupación Astronómica de Sabadell（萨巴德尔天文团）
We have analysed K2 light curves for more than 3,000 low mass stars in the $\sim$8 Myr old Upper Sco association, the $\sim$125 Myr age Pleiades open cluster and the $\sim$700 Myr old Hyades and Praesepe open clusters to determine stellar rotation rates. Many of these K2 targets show two distinct periods, and for the lowest mass stars in these clusters virtually all of these systems with two periods are photometric binaries. The most likely explanation is that we are detecting the rotation periods for both components of these binaries. We explore the evolution of the rotation rate in both comp…
An algorithm to calculate the relative orbit, ephemeris, and individual masses of unresolved astrometric binaries. Example of application on the newest Gaia DR3 binaries: the ESMORGA catalog
paired: A Statistical Framework for Detecting Stellar Binarity with Gaia RVs. I. Sensitivity to Unresolved Binaries
University of Florida（佛罗里达大学）；Center for Computational Astrophysics, Flatiron Institute（纽约市立学院西蒙斯数据科学研究所计算天体物理中心）；School of Physics & Astronomy, Monash University（蒙纳士大学物理与天文学院）；Center of Excellence for Astrophysics in Three Dimensions (ASTRO-3D)（三维天体物理学卓越中心）
Unresolved triple systems in the aged open cluster Trumpler 19: Discovery, confirmation, and implications
Universidad Andres Bello（安德斯贝洛大学）；Vatican Observatory（梵蒂冈天文台）；Universidade Federal de Santa Catarina（圣卡塔琳娜联邦大学）；European Southern Observatory（欧洲南方天文台）；University of Hertfordshire（赫特福德大学）；Universidad Bernardo O’Higgins（贝尔纳多·奥希金斯大学）；Universidad de Antofagasta（安托法加斯塔大学）
We examine the distribution of on-sky relative velocities for wide binaries previously assembled from GAIA DR2 data and focus on the origin of the high velocity tail of apparently unbound systems which may be interpreted as evidence for non-Newtonian gravity in the weak field limit. We argue that this tail is instead explicable in terms of a population of hidden triples, i.e. cases where one of the components of the wide binary is itself a close binary unresolved in the GAIA data. In this case the motion of the photocentre of the inner pair relative to its barycentre affects the apparent relat…
Astrometric modeling of unresolved variable binary systems. II. Application to Gaia epoch astrometry of nearby pulsating and convective red giants
KU Leuven（荷语鲁汶大学）；Observatoire de Paris, Université PSL, Sorbonne Université, Université Paris Cité, CY Cergy Paris Université, CNRS（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）；French-Chilean Laboratory for Astronomy, IRL 3386, CNRS and U. de Chile（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）
The Transiting Exoplanet Survey Satellite (TESS) is conducting a two-year wide-field survey searching for transiting exoplanets around nearby bright stars that will be ideal for follow-up characterization. To facilitate studies of planet compositions and atmospheric properties, accurate and precise planetary radii need to be derived from the transit light curves. Since 40 - 50% of exoplanet host stars are in multiple star systems, however, the observed transit depth may be diluted by the flux of a companion star, causing the radius of the planet to be underestimated. High angular resolution im…
Towards breaking the degeneracy between stellar ages and unresolved multiplicity
Universitat de Barcelona（巴塞罗那大学）；Institut d’Estudis Espacials de Catalunya（加泰罗尼亚空间研究所）；Instituto de Astrofísica de Canarias（加那利天体物理研究所）；Universidad de La Laguna（拉古纳大学）；Leibniz-Institut für Astrophysik Potsdam（波茨坦阿诺德·爱因斯坦天体物理研究所）
The high-quality OmegaCAM photometry of the 3x3 deg around the Orion Nebula Cluster (ONC) in r, and i filters by Beccari et al.(2017) revealed three well-separated pre-main sequences in the color-magnitude diagram (CMD). The objects belonging to the individual sequences are concentrated towards the center of the ONC. The authors concluded that there are two competitive scenarios: a population of unresolved binaries and triples with an exotic mass ratio distribution, or three stellar populations with different ages. We use Gaia DR2 in combination with the photometric OmegaCAM catalog to test an…
Unresolved triples in the open cluster NGC 2437 (M 46) confirmed by the KMOS VVVX-GalCen Spectroscopic Survey
Universidad Andres Bello（安德斯贝洛大学）；Vatican Observatory（梵蒂冈天文台）；Universidad Nacional de Córdoba（科尔多瓦国立大学）；Universidade Federal de Santa Catarina（圣卡塔琳娜联邦大学）；Universidad Bernardo O’Higgins（贝尔纳多·奥希金斯大学）；Universidad de Antofagasta（安托法加斯塔大学）；European Southern Observatory（欧洲南方天文台）
利用 KMOS VVVX-GalCen 光谱巡天的视向速度，确认了开放星团 NGC 2437 中存在未分辨三合星系统序列，并发现其比例高于较老星团，表明这些系统会合并或瓦解。
Binary stars play a vital role in astrophysical research, as a good fraction of stars are in binaries. Binary fraction (BF) is known to change with stellar mass in the Galactic field, but such studies in clusters require binary identification and membership information. Here, we estimate the total and spectral-type-wise high mass-ratio (HMR) BF ($f^{0.6}$) in 23 open clusters using unresolved binaries in color-magnitude diagrams using \textit{Gaia} DR2 data. We introduce the segregation index (SI) parameter to trace mass segregation of HMR (total and mass-wise) binaries and the reference popul…
The age-metallicity relation is a fundamental tool for constraining the chemical evolution of the Galactic disc. In this work we analyse the observational properties of this relation using binary stars that have not interacted consisting of a white dwarf - from which we can derive the total age of the system - and a main sequence star - from which we can derive the metallicity as traced by the [Fe/H] abundances. Our sample consists of 46 widely separated, but unresolved spectroscopic binaries identified within the Sloan Digital Sky Survey, and 189 white dwarf plus main sequence common proper m…
