Unresolved Binaries and Galactic Clusters’ Mass Estimates

Borodina, O. I.; Seleznev, A. F.; Carraro, G.; Данилов, В. А.

doi:10.3847/1538-4357/ab08e5

Cited by 24 publications

(34 citation statements)

References 39 publications

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“…Therefore, binaries are ideal tracers for investigating the formation and evolution of OCs, as well as the dependence on their forming locations and environments. Furthermore, binary stars are essential in determining the total mass (Borodina et al 2019) and the stellar mass function (Kroupa & Boily 2002) of OCs.…”

Section: Introductionmentioning

confidence: 99%

Modelling unresolved binaries of open clusters in color-magnitude diagram. I. method and application of NGC3532

Li,

Shao,

et al. 2020

Preprint

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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 b and binary massratio 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 determine the main sequence ridge line and its scatter from the observed CMD as model input. As a first example, we apply the method to the open cluster NGC3532 with the Gaia DR2 photometry. For the cluster members within a magnitude range corresponding to FGK dwarfs, we obtain f b = 0.267 ± 0.019 and γ q = −0.10 ± 0.22 for binaries with mass ratio q > 0.2. The f b value is consistent with the previous work on NGC3532 and smaller than that of field stars. The close to zero γ q indicates that the mass ratios of binaries follow a nearly uniform distribution. For the first time, we unveil that the stars with smaller mass or in the inner region tend to have lower f b and more positive value of γ q due to the lack of low mass-ratio binaries. The clear dependences of binary properties on mass and radius are most likely caused by the internal dynamics.

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Section: Introductionmentioning

confidence: 99%

Modelling unresolved binaries of open clusters in color-magnitude diagram. I. method and application of NGC3532

Li,

Shao,

et al. 2020

Preprint

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“…η = 0.3) is expected (see e.g. Gizis & Reid 1995;Bouvier et al 2001;Böhm-Vitense 2007;Boudreault et al 2010;Khalaj & Baumgardt 2013;Sheikhi et al 2016;Borodina et al 2019;Li et al 2020) even if the distribution of η can be quite large, ranging from about 30% to 70% (Sollima et al 2010). Moreover, the value of η = 0.3 we adopted is fully suitable for clusters Praesepe (e.g.…”

Section: Towards a Practical Applications In The Gaia Eramentioning

confidence: 86%

Goodness-of-fit test for isochrone fitting in the Gaia era. Statistical assessment of the error distribution

Valle,

Dell'Omodarme,

Tognelli

2021

Preprint

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Context. The increasing precision in observational data made available by recent surveys means that the reliability of stellar models can be tested. For this purpose, a firm theoretical basis is crucial for evaluating the agreement of the data and theoretical predictions. Aims. This paper presents a rigorous derivation of a goodness-of-fit statistics for colour-magnitude diagrams (CMD). We discuss the reliability of the underlying assumptions and their validity in real-world testing. Methods. We derived the distribution of the sum of squared Mahalanobis distances of stellar data and theoretical isochrone for a generic set of data and models. We applied this to the case of synthetic CMDs that were constructed to mimic real data of open clusters in the GAIA sample. Then, we analysed the capability of distinguishing among different sets of input physics and parameters that were used to compute the stellar models. To do this, we generated synthetic clusters from isochrones computed with these perturbed quantities, and we evaluated the goodness-of-fit with respect to the reference unperturbed isochrone. Results. We show that when r magnitudes are available for each of the N observational objects and p hyperparameters are estimated in the fit, the error distribution follows a χ 2 distribution with (r − 1)N − p degrees of freedom. We show that the linearisation of the isochrone between support points introduces negligible deviation from this result. We investigated the possibility of detecting the effects on stellar models that are induced when the following physical quantities were varied: convective core overshooting efficiency, 14 N(p, γ) 15 O reaction rate, microscopic diffusion velocities, outer boundary conditions, and colour transformation (bolometric corrections). We conducted the analysis at three different ages, 150 Myr, 1 Gyr, and 7 Gyr, and accounted for errors in photometry from 0.003 mag to 0.03 mag. The results suggest that it is possible to detect the effect induced by only some of the perturbed quantities. The effects induced by a change in the diffusion velocities or in the 14 N(p, γ) 15 O reaction rate are too small to be detected even when the smallest photometric uncertainty is adopted. A variation in the convective core overshooting efficiency was detectable only for photometric errors of 0.003 mag and only for the 1 Gyr case. The effects induced by the outer boundary conditions and the bolometric corrections are the largest; the change in outer boundary conditions is detected for photometric errors below about 0.01 mag, while the variation in bolometric corrections is detectable in the whole photometric error range. As a last exercise, we addressed the validity of the goodness-of-fit statistics for real-world open cluster CMDs, contaminated by field stars or unresolved binaries. We assessed the performance of a data-driven cleaning of observations, aiming to select only single stars in the main sequence from Gaia photometry. This showed that this selection is possible only for a very precise photo...

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“…The evolution of stars in close binary systems leads to the formation of 'exotic' stars: blue straggler stars, cataclysmic variable stars and so forth (Hurley et al 2001;Carraro & Seleznev 2011;Hong et al 2017). Finally, one needs to take unresolved binary and multiple stars into full account when obtaining photometric estimates of open cluster masses (Borodina et al 2019;Rastello et al 2020;Borodina et al 2021) or spectroscopic estimates of their dynamical mass (Seleznev et al 2017;Rastello et al 2020).…”

Section: Introductionmentioning

confidence: 99%

“…However, Li et al (2017) had found α = 0.6 − 0.8 for NGC6362, NGC6652, and NGC6838. In open clusters the binary ratio is α 0.3 (see Borodina et al (2019) for a review, and Niu et al (2020)). The binary ratio for the field stars seems to be even larger (see Duchêne & Kraus (2013) for a review).…”

Section: Introductionmentioning

confidence: 99%

Unresolved Binaries in the Intermediate Mass Range in the Pleiades Star Cluster

Malofeeva,

Seleznev,

Carraro

2022

Preprint

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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 ⊙ . The binary star ratio is found to be between 0.54±0.11 and 0.70±0.14. On the other hand, the ratio of systems with multiplicity more than 2 is between 0.10±0.00 and 0.14±0.01. The distribution of the component mass ratio q has been approximated by a power law with the exponent between -0.53±0.10 and -0.63±0.22. Below 0.5 M ⊙ , we expect a large number of brown dwarfs among secondary components.

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Unresolved Binaries and Galactic Clusters’ Mass Estimates

Cited by 24 publications

References 39 publications

Modelling unresolved binaries of open clusters in color-magnitude diagram. I. method and application of NGC3532

Modelling unresolved binaries of open clusters in color-magnitude diagram. I. method and application of NGC3532

Goodness-of-fit test for isochrone fitting in the Gaia era. Statistical assessment of the error distribution

Unresolved Binaries in the Intermediate Mass Range in the Pleiades Star Cluster

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