Contribution of Binary Stars to the Velocity Dispersion inside OB Associations with Gaia DR2 Data

По данным Gaia DR2 в радиусе 100 пк от Солнца исследованы двойные звезды с общим собственным движением до расстояния между компонентами 3 пк. Для исключения возможных случайных совпадений смоделирована искусственная выборка случайных пар. Показано, что принятый способ отбора пар с общим собственным движением делает загрязнение выборки случайными совпадениями незначительным даже при больших расстояниях между компонентами; величина такого загрязнения оценена численно. Получено бимодальное распределение по логарифму расстояния между компонентами, демонстрирующее для очень широких пар минимум, связанный с распадом систем, на расстоянии ≈ 0.5 пк, и дальнейший рост, формируемый распавшимися, медленно расходящимися компонентами. Binary and common proper motion stars within 100 pc of the Sun are being investigated using Gaia DR2 data. An artificial random pairs sample is constructed to exclude possible random pairing contamination. Numerical estimation of this contamination shows that the chosen method to select the common proper motion stars yields little contamination even at high separations. In a logarithmic scale the separation distribution appear to have a minimum at ≈ 0.5 pc, most likely related to binary star dissolution, with further increase formed by dissolved, slowly distancing components.

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Unlocking Galactic Wolf–Rayet stars with Gaia DR2 – II. Cluster and association membership

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1290 ◽

2020 ◽

Vol 495 (1) ◽

pp. 1209-1226 ◽

Cited By ~ 2

Author(s):

Gemma Rate ◽

Paul A Crowther ◽

Richard J Parker

Keyword(s):

Near Infrared ◽

Galactic Centre ◽

Low Density ◽

Cluster Membership ◽

Star Forming ◽

Star Forming Regions ◽

Centre Region ◽

Ob Associations ◽

Mass Segregation ◽

Gaia Dr2

ABSTRACT Galactic Wolf–Rayet (WR) star membership of star-forming regions can be used to constrain the formation environments of massive stars. Here, we utilize Gaia DR2 parallaxes and proper motions to reconsider WR star membership of clusters and associations in the Galactic disc, supplemented by recent near-infrared studies of young massive clusters. We find that only 18–36 per cent of 553 WR stars external to the Galactic Centre region are located in clusters, OB associations or obscured star-forming regions, such that at least 64 per cent of the known disc WR population are isolated, in contrast with only 13 per cent of O stars from the Galactic O star Catalogue. The fraction located in clusters, OB associations or star-forming regions rises to 25–41 per cent from a global census of 663 WR stars including the Galactic Centre region. We use simulations to explore the formation processes of isolated WR stars. Neither runaways, nor low-mass clusters, are numerous enough to account for the low cluster membership fraction. Rapid cluster dissolution is excluded as mass segregation ensures WR stars remain in dense, well-populated environments. Only low-density environments consistently produce WR stars that appeared to be isolated during the WR phase. We therefore conclude that a significant fraction of WR progenitors originate in low-density association-like surroundings which expand over time. We provide distance estimates to clusters and associations host to WR stars, and estimate cluster ages from isochrone fitting.

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Testing modified gravity with wide binaries in Gaia DR2

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz1898 ◽

2019 ◽

Vol 488 (4) ◽

pp. 4740-4752 ◽

Cited By ~ 8

Author(s):

Charalambos Pittordis ◽

Will Sutherland

Keyword(s):

Dark Matter ◽

Binary Stars ◽

Modified Gravity ◽

Simulated Data ◽

Peak Shift ◽

Wide Binary ◽

A Value ◽

Modified Gravity Theories ◽

Clear Peak ◽

Gaia Dr2

ABSTRACT Several recent studies have shown that very wide binary stars can potentially provide an interesting test for modified-gravity theories which attempt to emulate dark matter; these systems should be almost Newtonian according to standard dark-matter theories, while the predictions for MOND-like theories are distinctly different, if the various observational issues can be overcome. Here we explore an observational application of the test from the recent Gaia DR2 data release: we select a large sample of ∼24 000 candidate wide binary stars with distance $\lt 200 \, {\rm pc}$ and magnitudes G < 16 from Gaia DR2, and estimated component masses using a main-sequence mass–luminosity relation. We then compare the frequency distribution of pairwise relative projected velocity (relative to circular-orbit value) as a function of projected separation; these distributions show a clear peak at a value close to Newtonian expectations, along with a long ‘tail’ which extends to much larger velocity ratios; the ‘tail’ is considerably more numerous than in control samples constructed from DR2 with randomized positions, so its origin is unclear. Comparing the velocity histograms with simulated data, we conclude that MOND-like theories without an external field effect (ExFE) are strongly inconsistent with the observed data since they predict a peak-shift in clear disagreement with the data; testing MOND-like theories with an ExFE is not decisive at present, but has good prospects to become decisive in future with improved modelling or understanding of the high-velocity tail, and additional spectroscopic data.

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Distance scale for high-luminosity stars in OB associations and in field with Gaia DR2. Spurious systematic motions

Astrophysics and Space Science ◽

10.1007/s10509-020-03827-0 ◽

2020 ◽

Vol 365 (7) ◽

Author(s):

A. M. Melnik ◽

A. K. Dambis

Keyword(s):

Distance Scale ◽

High Luminosity ◽

Ob Associations ◽

Gaia Dr2

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Mining of the Milky Way Star Archive Gaia-DR2. Searching for Binary Stars in Planetary Nebulae

Proceedings ◽

10.3390/proceedings2020054052 ◽

2020 ◽

Vol 54 (1) ◽

pp. 52

Author(s):

Iker González-Santamaría ◽

Minia Manteiga ◽

Carlos Dafonte ◽

Arturo Manchado ◽

Ana Ulla

Keyword(s):

Binary Stars ◽

Binary Systems ◽

Planetary Nebulae ◽

Central Star ◽

Separation Distance ◽

Proper Motions ◽

Use Of Data ◽

Stellar Sources ◽

Stellar Envelopes ◽

Gaia Dr2

The aim of this work is to search for binary stars associated to planetary nebulae (ionized stellar envelopes in expansion), by mining the astronomical archive of Gaia DR2, that is composed by around 1.7 billion stellar sources. For this task, we selected those objects with coincident astrometric parameters (parallaxes and proper motions) with the corresponding central star, among a sample of 211 planetary nebulae. By this method, we found eight binary systems, and we obtained their components positions, separations, temperatures and luminosities, as well as some of their masses and ages. In addition, we estimated the probability for each companion star of having been detected by chance and we analyzed how the number of false matches increase as the separation distance between both stars gets larger. All these procedures have been carried out making use of data mining techniques.

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MOCCA Survey Database: Extra Galactic Globular Clusters. I. Method and first results

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa4027 ◽

2021 ◽

Author(s):

A Leveque ◽

M Giersz ◽

M Paolillo

Keyword(s):

Globular Clusters ◽

Surface Brightness ◽

Velocity Dispersion ◽

Structural Parameters ◽

Dynamical Evolution ◽

Central Surface ◽

First Results ◽

Preliminary Study ◽

Galactic Globular Clusters ◽

Gaia Dr2

Abstract Over the last few decades, exhaustive surveys of extra Galactic globular clusters (EGGCs) have become feasible. Only recently, limited kinematical information of globular clusters (GCs) were available through Gaia DR2 spectroscopy and also proper motions. On the other hand, simulations of GCs can provide detailed information about the dynamical evolution of the system. We present a preliminary study of EGGCs- properties for different dynamical evolutionary stages. We apply this study to 12 Gyr-old GCs simulated as part of the MOCCA Survey Database. Mimicking observational limits, we consider only a subssample of the models in the database, showing that it is possible to represent observed Milky Way GCs. In order to distinguish between different dynamical states of EGGCs, at least three structural parameters are necessary. The best distinction is achieved by considering the central parameters, those being observational core radius, central surface brightness, ratio between central and half-mass velocity dispersion, or similarly considering the central color, the central V magnitude and the ratio between central and half-mass radius velocity dispersion, although such properties could be prohibitive with current technologies. A similar but less solid result is obtained considering the average properties at the half-light radius, perhaps accessible presently in the Local Group. Additionally, we mention that the color spread in EGGCs due to internal dynamical models, at fixed metallcity, could be just as important due to the spread in metallicity.

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Internal motions in OB associations with Gaia DR2

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa454 ◽

2020 ◽

Vol 493 (2) ◽

pp. 2339-2351 ◽

Cited By ~ 8

Author(s):

A M Melnik ◽

A K Dambis

Keyword(s):

Expansion Velocity ◽

Giant Molecular Clouds ◽

Proper Motions ◽

Ob Stars ◽

Internal Motions ◽

Ob Associations ◽

Stellar Masses ◽

Formation Efficiency ◽

First Time ◽

Gaia Dr2

ABSTRACT We study the motions inside 28 OB associations with the use of Gaia DR2 proper motions. The average velocity dispersion calculated for 28 OB associations including more than 20 stars with Gaia DR2 proper motion is σv = 4.5 km s−1. The median virial and stellar masses of OB associations are Mvir = 8.9 × 105 and Mst = 8.1 × 103 M⊙, respectively. The median star-formation efficiency in parent giant molecular clouds appears to be ϵ = 1.2 per cent. Gaia DR2 proper motions confirm the expansion in the Per OB1, Car OB1, and Sgr OB1 associations found earlier with Gaia DR1 data. We also detect the expansion in Gem OB1, Ori OB1, and Sco OB1 associations, which became possible for the first time now when analysed with Gaia DR2 proper motions. The analysis of the distribution of OB stars in the Per OB1 association shows the presence of a shell-like structure with the radius of 40 pc. Probably, the expansion of the Per OB1 association started with the velocity greater than the present-day expansion velocity equal to 5.0 ± 1.7 km s−1.

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Kinematics of OB-associations in the 3-kpc solar neighborhood

Proceedings of the International Astronomical Union ◽

10.1017/s1743921318008335 ◽

2018 ◽

Vol 14 (S345) ◽

pp. 39-42

Author(s):

Anna M. Melnik ◽

Andrei K. Dambis ◽

Elena V. Glushkova ◽

Pertti Rautiainen

Keyword(s):

Velocity Dispersion ◽

Local System ◽

Solar Neighborhood ◽

Proper Motions ◽

One Dimensional ◽

The Galaxy ◽

Average Residual ◽

Ob Associations ◽

Stellar Masses ◽

Formation Efficiency

AbstractWe use Gaia (DR1, DR2) stellar proper motions to study the kinematics of OB-associations. The average one-dimensional velocity dispersion inside 18 OB-associations with more than 10 Gaia DR1 stars is σv = 3.9 km s−1. The median virial and stellar masses of OB-associations are equal to 7×105 and 9 × 103 solar masses, respectively. The median star-formation efficiency is ε = 2.1%. We have found the expansion in several OB-associations. Models of the Galaxy with a two-component outer ring R1R2 can reproduce the average residual velocities of OB-associations in the Perseus, Sagittarius and Local System complexes.

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