Modeling Unresolved Binaries of Open Clusters in the Color–Magnitude Diagram. I. Method and Application of NGC 3532

Context. Blue straggler stars (BSSs) are observed in Galactic globular clusters and old open clusters. The radial distribution of BSSs has been used to diagnose the dynamical evolution of globular clusters. For the first time, with a reliable sample of BSSs identified with Gaia DR2, we conduct such an analysis for an open cluster. Aims. We aim to identify members, including BSSs, of the oldest known Galactic open cluster Berkeley 17 with the Gaia DR2 proper motions and parallaxes. We study the radial distribution of the BSS population to understand the dynamical evolution of the cluster. Methods. We selected cluster members to populate the colour magnitude diagram in the Gaia filters. Cluster parameters are derived using the brightest members. The BSSs and giant branch stars are identified, and their radial distributions are compared. The segregation of BSSs is also evaluated with respect to the giant branch stars using the minimum spanning tree (MST) analysis. Results. We determine Berkeley 17 to be at 3138.6−352.9+285.5 pc. We find 23 BSS cluster members, only two of which were previously identified. We find a bimodal radial distribution of BSSs supported by findings from the MST method. Conclusions. The bimodal radial distribution of BSSs in Berkeley 17 indicates that they have just started to sink towards the cluster centre, placing Berkeley 17 with globular clusters of intermediate dynamical age. This is the first such determination for an open cluster.

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Investigation on fundamental plane of open clusters

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317008869 ◽

2017 ◽

Vol 13 (S334) ◽

pp. 331-332

Author(s):

Xiao-Ying Pang ◽

Chien-Cheng Lin

Keyword(s):

Radial Velocity ◽

Surface Brightness ◽

Velocity Dispersion ◽

Open Clusters ◽

Fundamental Plane ◽

Average Surface ◽

Magnitude Diagram ◽

Formation And Evolution

AbstractThe fundamental plane (FP) is the relation between the surface brightness (I), velocity dispersion (σ) and radius (R). The tilt of FP from the virial plane (R = σ2 I) not only tells the dynamical states of the system but also its formation and evolution. We motivate to looking for an FP in Galactic open clusters (OCs). To form a sample of OCs, we access the most recent DR 14 data from the SDSS/APOGEE2 and the Gaia-ESO survey. Membership of stars is determined via radial velocity and metallicity, plus star’s location in the color-magnitude diagram. Besides the velocity dispersion (σrv) obtained from SDSS/APOGEE2 & Gaia-ESO, the average surface brightness (IKs), and apparent radii (r2) of OCs are taken from known OC catalog. A weak relation is found: log(r2) ∝ -0.34 * log(σ) - 0.08 * IKs. An implication of this FP needs further investigation.

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Determination of astrophysical parameters of open clusters using classical and semi-automated isochrone-fitting methods

Proceedings of the International Astronomical Union ◽

10.1017/s1743921309991268 ◽

2009 ◽

Vol 5 (S266) ◽

pp. 352-352

Author(s):

Virginia Mello Alves ◽

Eduardo Bica ◽

Daniela Borges Pavani

Keyword(s):

Open Clusters ◽

Parameter Uncertainties ◽

Optical Photometry ◽

Automated Method ◽

Magnitude Diagram

AbstractWhen we use optical isochrone-fitting solutions from the literature to 2mass CMDs, they are often not the best solutions in the infrared domain. We analysed 10 open clusters with 2mass, nine of them previously studied with optical photometry (NGC 1245, NGC 1342, NGC 1502, NGC 2104, NGC 2204, NGC 2243, NGC 2281, NGC 6709 and NGC 744) and one using integrated spectroscopy (BH 132). The study involved the classical (by eye) and a semi-automated method of isochrone fitting. We used the solutions of the first method as input for the second, looking for refined solutions. The semi-automated method uses a synthetic color–magnitude diagram (CMD), based on different Padova isochrones, to compare with the observed CMDs by means of likelihood statistics. The derived astrophysical parameters are age, distance and reddening values. The present results show better fits than those implied by the optical values. We also show that the semi-automated method decreases the parameter uncertainties.

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Extended main sequence turnoffs in open clusters as seen by Gaia – II. The enigma of NGC 2509

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz3128 ◽

2019 ◽

Vol 491 (2) ◽

pp. 2129-2136 ◽

Cited By ~ 4

Author(s):

M de Juan Ovelar ◽

S Gossage ◽

S Kamann ◽

N Bastian ◽

C Usher ◽

...

Keyword(s):

Stellar Evolution ◽

Main Sequence ◽

Narrow Range ◽

Open Cluster ◽

Open Clusters ◽

Stellar Rotation ◽

Rotation Rates ◽

Magnitude Diagram ◽

Stellar Density

ABSTRACT We investigate the morphology of the colour–magnitude diagram (CMD) of the open cluster NGC 2509 in comparison with other Galactic open clusters of similar age using Gaia photometry. At ${\sim}900\,\rm {Myr}$ Galactic open clusters in our sample all show an extended main sequence turnoff (eMSTO) with the exception of NGC 2509, which presents an exceptionally narrow CMD. Our analysis of the Gaia data rules out differential extinction, stellar density, and binaries as a cause for the singular MSTO morphology in this cluster. We interpret this feature as a consequence of the stellar rotation distribution within the cluster and present the analysis with mesa Isochrones and Stellar Tracks (MIST) stellar evolution models that include the effect of stellar rotation on which we based our conclusion. In particular, these models point to an unusually narrow range of stellar rotation rates (Ω/Ωcrit, ZAMS = [0.4, 0.6]) within the cluster as the cause of this singular feature in the CMD of NGC 2509. Interestingly, models that do not include rotation are not as good at reproducing the morphology of the observed CMD in this cluster.

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Fundamental parameters for 30 faint open clusters with Gaia EDR3 based on the more reliable members

Publications of the Astronomical Society of Japan ◽

10.1093/pasj/psab091 ◽

2021 ◽

Author(s):

Xu Ding ◽

Kai-Fan Ji ◽

Xu-Zhi Li ◽

Qi-Yuan Cheng ◽

Jin-Liang Wang ◽

...

Keyword(s):

Spatial Structure ◽

Spatial Clustering ◽

Open Cluster ◽

Open Clusters ◽

Monte Carlo Algorithm ◽

Structure Parameters ◽

Fundamental Parameters ◽

The Core ◽

Magnitude Diagram ◽

Fitting Parameters

Abstract An open cluster is an ideal region to study the evolution of stars. In this work, we use Gaia Early Data Release 3 (Gaia EDR3) to derive the fundamental parameters of 30 faint open clusters listed in the catalogue given by Cantat-Gaudin et al. (2018, A&A, 618, A93), but the G magnitude of all of the member stars of that catalogue is brighter than ∼18 mag. This catalogue does not provide isochrone fitting parameters and spatial structure parameters. We acquired the member stars of 30 open clusters using the Density-Based Spatial Clustering of Applications with Noise algorithm in Gaia EDR3. The G magnitude of the member stars using our method can be found down to ∼21 mag. The G-band, GBP-band, and GRP-band data of the member stars construct a good color–magnitude diagram, which can further ensure the precision of isochrone fitting. We also calculated the spatial structure parameters, which are the core radius and the limiting radius, using Markov chain Monte Carlo algorithm.

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Open clusters: a program to analyse the color–magnitude diagram with the help of stellar kinematic data

Proceedings of the International Astronomical Union ◽

10.1017/s1743921309991426 ◽

2009 ◽

Vol 5 (S266) ◽

pp. 385-385

Author(s):

Wilton S. Dias ◽

Thiago Costa Caetano

Keyword(s):

Radial Velocity ◽

Proper Motion ◽

Open Clusters ◽

Uncertain Parameters ◽

Kinematic Data ◽

Magnitude Diagram ◽

The Mean ◽

Stellar Kinematic

AbstractWe constructed a program that allows one to use simultaneously and interactively photometric and astrometric stellar data (proper motion) to analyse color–color and color–magnitude diagrams. With this program, we are able to determine, based on photometric membership, the distance and age as well as the mean proper motion and radial velocity of several open clusters which had very uncertain parameters in previous analyses.

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The LMC Globular Cluster Hodge 11 (=SL 868)

Symposium - International Astronomical Union ◽

10.1017/s0074180900039863 ◽

1984 ◽

Vol 108 ◽

pp. 43-44

Author(s):

L. L. Stryker ◽

J. M. Nemec ◽

J. E. Hesser ◽

R.D. McClure

Keyword(s):

Globular Clusters ◽

Main Sequence ◽

Star Cluster ◽

Open Clusters ◽

Rr Lyrae Stars ◽

Rr Lyrae ◽

Magnitude Diagram ◽

The Galaxy ◽

Lyrae Stars ◽

Termination Point

The age of the star cluster H11 has been controversial for a number of years. The color-magnitude diagram (CMD) of Walker (1979) to V=21.5 was interpreted as an “…evolved main-sequence, whose termination point corresponds to an age of about 0.6 Gyr, but with a giant branch which is displaced blueward by about Δ (B-V)o=0.4 from the positions of the giant branches of open clusters of similar age in our Galaxy.” On the other hand, the integrated colors are similar to those of metal-poor globular clusters in the Galaxy (Freeman and Gascoigne 1977, and references therein), and “…incompatible with an age of say 0.3 Gyr.” Searle, Wilkinson and Bagnuolo (1980) classify it as Group VII, the oldest group. The system has no RR Lyrae stars (Graham and Nemec 1984).

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Open Clusters and Stellar Evolution

Symposium - International Astronomical Union ◽

10.1017/s0074180900091841 ◽

1980 ◽

Vol 85 ◽

pp. 195-214

Author(s):

Gretchen L.H. Harris

Keyword(s):

Stellar Evolution ◽

Initial Conditions ◽

Dynamical Evolution ◽

Open Clusters ◽

Potential Importance ◽

Helium Burning ◽

The Core ◽

Magnitude Diagram

Several topics relevant to the study of stellar evolution through open clusters are discussed. These include composite color-magnitude diagrams, the need for thorough studies of populous clusters, parameters affecting the core helium burning stage, and the potential importance of initial conditions and dynamical evolution on the cluster color-magnitude diagram.

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Study of open cluster NGC 5617 in Gaia era

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319008159 ◽

2019 ◽

Vol 14 (S353) ◽

pp. 22-23

Author(s):

D. Bisht ◽

Qingfeng Zhu

Keyword(s):

Data Base ◽

Proper Motion ◽

Open Cluster ◽

Open Clusters ◽

Fundamental Parameters ◽

Magnitude Diagram ◽

Cluster Properties ◽

Open Question ◽

Gaia Dr2

AbstractIdentification of member stars in open clusters is still an open question. Thanks to Gaia DR2 data base, which improves our statistics regarding true members in clusters to understand cluster properties much better way. In this paper, we identify the cluster members using proper motion and colour magnitude diagram for NGC 5617. In addition to this, we have determined more precise fundamental parameters as well.

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Tests of Evolution Models Using Star Clusters

Highlights of Astronomy ◽

10.1017/s153929960001159x ◽

1995 ◽

Vol 10 ◽

pp. 423-427 ◽

Cited By ~ 1

Author(s):

J.-C. Mermilliod

Keyword(s):

Globular Clusters ◽

Main Sequence ◽

Open Clusters ◽

Surface Chemical ◽

Main Sequence Stars ◽

Element Abundances ◽

Detailed Surface ◽

Model Predictions ◽

Magnitude Diagram ◽

Red Giant

The fitting of isochrones over star-cluster colour-magnitude diagrams is a favourite test of stellar evolution models because it seems to be the easiest and most evident one: the star distribution in the colour-magnitude diagram represents a constant age locus, provided the clusters are old enough and the internal age dispersion is negligible. The ratios of evolved to main-sequence stars in open clusters, or of population along the red giant branch in globular clusters, could provide valuable tests, but it is difficult to estimate these ratios with small enough uncertainties. Furthermore the detailed surface chemical composition (element abundances and isotope ratios) is not known for many cluster stars and model predictions cannot be tested in various environments.Tests have been mostly devoted to the main sequence and the long debate between canonical precepts and core overshooting is still active. St others (1991) has argued that the use of the new opacities (Rogers & Iglesias 1992) reduces the necessity of adding overshooting to the models. Castellani et al (1992) computed extensive grids of models with canonical precepts. However, recent papers (Carraro et al. 1993; Meynet et al. 1993; Demarque et al. 1994) show that a moderate core overshooting (about 0.2 Hp) is still necessary. Basically, cluster observations call for more massive cores, whatever process is at work. An excellent review of the various ingredients included in models (equation of state, nuclear rates, opacities, convection) and the effects of their changes has been presented by Vandenberg (1991).

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