The Central Blue Straggler Population in Four Outer-Halo Globular Clusters

Beccari, G.; Lützgendorf, Nora; Olczak, C.; Ferraro, F. R.; Lanzoni, B.; Carraro, G.; Stetson, P. B.; Sollima, A.; Boffin, H. M. J.

doi:10.1088/0004-637x/754/2/108

Cited by 15 publications

(14 citation statements)

References 54 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Recent progress in understanding the origin and properties of BS in GCs has been enormous, mostly due to observations of GC cores with the Hubble telescope of Piotto et al (2004), Leigh et al (2007), Beccari et al (2012), Dalessandro et al (2013a), Dalessandro et al (2013b), andSanna et al (2014). A comprehensive review of observations and resulting conclusions can be found in Boffin et al (2014).…”

Section: Blue Stragglersmentioning

confidence: 99%

Model computations of blue stragglers and W UMa-type stars in globular clusters

Stępień

Kiraga

2015

A&A

View full text Add to dashboard Cite

Context. It was recently demonstrated that contact binaries occur in globular clusters (GCs) only immediately below turn-off point and in the region of blue straggler stars (BSs). In addition, observations indicate that at least a significant fraction of BSs in these clusters was formed by the binary mass-transfer mechanism. Aims. The aim of our present investigation is to obtain and analyze a set of evolutionary models of cool, close detached binaries with a low metal abundance, which are characteristic of GC. Methods. We computed the evolution of 975 models of initially detached, cool close binaries with different initial parameters. The models include mass exchange between components as well as mass and angular momentum loss due to the magnetized winds for very low-metallicity binaries with Z = 0.001. The models are interpreted in the context of existing data on contact binary and blue straggler members of GCs. The models are based on our recently developed code for evolutionary modeling of cool close and contact binaries. Results. The model parameters agree well with the observed positions of the GC contact binaries in the Hertzsprung-Russell diagram, and we achieve detailed parameters of several individual contact and near-contact binaries. Contact binaries in the lower part of the cluster main sequence are absent because there are no binaries with initial orbital periods shorter than 1.5 d. Contact binaries end their evolution as mergers that appear in the BS region. Binary-formed BSs populate the whole observed BS region in a GC, but a gap is visible between low-mass mergers that are concentrated along the zero-age main sequence and binary BSs occupying the red part of the BS region. Very few binary mergers are expected to rotate rapidly and/or possess chemical peculiarities resulting from the exposure of the layers processed by CNO nuclear reactions. All other binary mergers are indistinguishable from the collisionally formed mergers. The results show that binary-formed BSs may constitute at least a substantial fraction of all BSs in a GC.

show abstract

Section: Blue Stragglersmentioning

confidence: 99%

Model computations of blue stragglers and W UMa-type stars in globular clusters

Stępień

Kiraga

2015

A&A

View full text Add to dashboard Cite

show abstract

“…The Shallow Sample was used to determine the cluster center of gravity (C grav ) and the projected density profile from accurate star counts 7 , following the procedure already adopted and described, e.g., in Beccari et al (2012). The resulting value of C grav is α J2000 = 14 h 05 m 27 s .2, δ J2000 = +28 • 32 ′ 01.…”

Section: The Shallow Sample and The Bss Populationmentioning

confidence: 99%

Deep Multi-Telescope Photometry of NGC 5466. I. Blue Stragglers and Binary Systems

Beccari

Dalessandro²,

Lanzoni³

et al. 2013

ApJ

View full text Add to dashboard Cite

We present a detailed investigation of the radial distribution of blue straggler star (BSS) and binary populations in the Galactic globular cluster NGC 5466, over the entire extension of the system. We used a combination of data acquired with the Advanced Camera for Survey on board the Hubble Space Telescope, the LBC-blue mounted on the Large Binocular Telescope, and MEGACAM on the Canada-France-Hawaii Telescope. BSSs show a bimodal distribution with a mild central peak and a quite internal minimum. This feature is interpreted in terms of a relatively young dynamical age in the framework of the "dynamical clock" concept proposed by Ferraro et al. The estimated fraction of binaries is ∼6%-7% in the central region (r < 90 ) and slightly lower (∼5.5%) in the outskirts, at r > 200 . Quite interestingly, the comparison with the results of Milone et al. suggests that binary systems may also display a bimodal radial distribution, with the position of the minimum consistent with that of BSSs. If confirmed, this feature would give additional support to the scenario where the radial distribution of objects more massive than the average cluster stars is primarily shaped by the effect of dynamical friction. Moreover, this would also be consistent with the idea that the unperturbed evolution of primordial binaries could be the dominant BSS formation process in low-density environments.

show abstract

“…Ferraro et al (2012) showed that based on the BSS radial distribution with respect to that of the light (or reference stars), globular clusters can be classified into three families: Family I globular clusters have a flat distribution and are "dynamically young"; Family II globular clusters have a bimodal distribution, with a peak at the cluster center, a minimum at intermediate radii, a rise in the external regions (eg. Dalessandro et al 2009;Beccari et al 2012), and are evolving under efficient dynamical friction; Family III globular clusters have a central peak followed by a monotonically decreasing trend and are "dynamically old".…”

Section: Introductionmentioning

confidence: 99%

The blue straggler population of the old open cluster Berkeley 17

Bhattacharya¹,

Vaidya

Chen

et al. 2019

A&A

Self Cite

View full text Add to dashboard Cite

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 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 select 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 analysis. Results. We determine Berkeley 17 to be at 3138.6 +285.5 −352.9 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 center, placing Berkeley 17 with globular clusters of intermediate dynamical age. This is the first such determination for an open cluster.

show abstract

The Central Blue Straggler Population in Four Outer-Halo Globular Clusters

Cited by 15 publications

References 54 publications

Model computations of blue stragglers and W UMa-type stars in globular clusters

Model computations of blue stragglers and W UMa-type stars in globular clusters

Deep Multi-Telescope Photometry of NGC 5466. I. Blue Stragglers and Binary Systems

The blue straggler population of the old open cluster Berkeley 17

Contact Info

Product

Resources

About