scholarly journals Environmental Effects on the Globular Cluster Blue Straggler Population: a Statistical Approach

2007 ◽  
Vol 3 (S246) ◽  
pp. 369-370
Author(s):  
Alessia Moretti ◽  
Francesca De Angeli ◽  
Giampaolo Piotto
Keyword(s):  
Stellar Evolution ◽  
Globular Clusters ◽  
Statistical Approach ◽  
Principal Component ◽  
Formation Mechanisms ◽  
Homogeneous Sample ◽  
Blue Stragglers ◽  
Parent Cluster ◽  
Blue Straggler ◽  
Environmental Dependence

AbstractBlue stragglers stars (BSS) constitute an ubiquitous population of objects whose origin involves both dynamical and stellar evolution. We took advantage of the homogeneous sample of 56 Galactic globular clusters observed with WFPC2/HST by Piotto et al. (2002) to investigate the environmental dependence of the BSS formation mechanisms. We explore possible monovariate relations between the frequency of BSS (divided in different subsamples according to their location with respect to the parent cluster core radius and half mass radius) and the main parameters of their host GC. We also performed a Principal Component Analysis to extract the main parent cluster parameters which characterise the BSS family.

scholarly journals Observations of blue straggler stars in globular clusters

2006 ◽  
Vol 2 (14) ◽  
pp. 438-439
Author(s):  
Francesco R. Ferraro ◽  
Barbara Lanzoni
Keyword(s):  
Globular Clusters ◽  
Binary Systems ◽  
Stellar Population ◽  
Main Sequence ◽  
Formation Mechanisms ◽  
Main Sequence Stars ◽  
Blue Stragglers ◽  
Photometric And Spectroscopic Observations ◽  
Blue Straggler ◽  
Dynamical Simulations

AbstractBlue stragglers stars (BSS) define a sparsely populated sequence extending to higher luminosity than the turnoff point of normal main sequence stars in the color magnitude diagrams of stellar aggregates, thus mimicking a rejuvenated (more massive) stellar population. The nature of these stars has been a puzzle for many years and their formation mechanism is not completely understood, yet. Two mechanisms have been proposed to produce BSS: (i) the mass transfer in binary systems; and ((ii) the merger of two stars induced by stellar interactions. In this contribution we schematically report on the main properties of BSS in globular clusters (GCs) in the light of the most recent photometric and spectroscopic observations. These results, combined with dynamical simulations, indicate that both the proposed formation mechanisms play an important role in the production of BSS in GCs.

scholarly journals Observations and Simulations of the Blue Straggler Star Radial Distribution: Clues on the Formation Mechanisms

2007 ◽  
Vol 3 (S246) ◽  
pp. 326-330
Author(s):  
Barbara Lanzoni
Keyword(s):  
Mass Transfer ◽  
Monte Carlo ◽  
Radial Distribution ◽  
Globular Clusters ◽  
Formation Mechanisms ◽  
Wide Field ◽  
Field Observations ◽  
Blue Stragglers ◽  
Blue Straggler ◽  
Dynamical Simulations

AbstractBy means of high-resolution and wide-field observations in the UV and optical bands we have derived the radial distribution of the Blue Stragglers Star (BSS) population in a number of galactic globular clusters. Monte-Carlo dynamical simulations have then been used to interpret the observed radial distributions in terms of percentage of collisional and mass-transfer BSS populating each cluster. I will present the main results thus obtained and an overall cluster–to–cluster comparison for the whole sample collected so far, mainly focusing on the clues that such an approach provides about the BSS formation mechanisms.

scholarly journals Blue Straggler Stars in Galactic Globular Clusters: Tracing the Effect of Dynamics on Stellar Evolution

2007 ◽  
Vol 3 (S246) ◽  
pp. 281-290
Author(s):  
Francesco R. Ferraro ◽  
Barbara Lanzoni
Keyword(s):  
Chemical Composition ◽  
Radial Distribution ◽  
Stellar Evolution ◽  
Globular Clusters ◽  
Blue Stragglers ◽  
Blue Straggler ◽  
Galactic Globular Clusters

AbstractIn this contribution we review the main observational properties of Blue Stragglers Stars (BSS) in galactic GCs. A flower of results on the BSS frequency, radial distribution, and chemical composition are presented and discussed.

scholarly journals Blue stragglers in star clusters and the conventional SSP models

2009 ◽  
Vol 5 (S266) ◽  
pp. 556-556
Author(s):  
Yu Xin ◽  
Richard de Grijs ◽  
Licai Deng ◽  
Pavel Kroupa
Keyword(s):  
Stellar Evolution ◽  
Stellar Population ◽  
Broad Band ◽  
Star Clusters ◽  
Open Clusters ◽  
Formation Mechanisms ◽  
Evolution Theory ◽  
Blue Stragglers ◽  
Blue Straggler ◽  
Conventional Picture

AbstractThe presence of blue straggler stars (BSs) as secure members of star clusters poses a major challenge to the conventional picture of simple stellar population (SSP) models. The models are based on the stellar evolution theory of single stars, while the major formation mechanisms of BSs are all correlated with stellar interactions. Based on a sufficient working sample including 100 Galactic open clusters, one Galactic globular cluster, and seven Magellanic Cloud star clusters, we discuss the modifications of the properties of broad-band colors and Lick indices of the standard SSP models due to BS populations.

scholarly journals The origin of the two populations of blue stragglers in M30

2019 ◽  
Vol 621 ◽  
pp. L10 ◽  
Author(s):  
S. Portegies Zwart
Keyword(s):  
Stellar Evolution ◽  
Main Sequence ◽  
The Other ◽  
Core Collapse ◽  
Blue Stragglers ◽  
The Core ◽  
Constant Rate ◽  
Blue Straggler ◽  
Binary Evolution ◽  
Two Populations

We analyze the position of the two populations of blue stragglers in the globular cluster M30 in the Hertzsprung–Russell diagram. Both populations of blue stragglers are brighter than the cluster’s turn-off, but one population, the blue blue-stragglers, aligns along the zero-age main sequence whereas the other, red population is elevated in brightness (or color) by ∼0.75 mag. Based on stellar evolution and merger simulations we argue that the red population, which composes about 40% of the blue stragglers in M 30, has formed at a constant rate of ∼2.8 blue stragglers per gigayear over the last ∼10 Gyr. The blue population on the other hand formed in a burst that started ∼3.2 Gyr ago at a peak rate of 30 blue stragglers per gigayear with an e-folding time scale of 0.93 Gyr. We speculate that the burst resulted from the core collapse of the cluster at an age of about 9.8 Gyr, whereas the constantly formed population is the result of mass transfer and mergers through binary evolution. In this scenario, about half the binaries in the cluster effectively result in a blue straggler.

scholarly journals Exotic populations in globular clusters: blue stragglers as tracers of the internal dynamical evolution of stellar systems

2014 ◽  
Vol 10 (S312) ◽  
pp. 171-180
Author(s):  
Francesco R. Ferraro
Keyword(s):  
Radial Distribution ◽  
Globular Clusters ◽  
Stellar Population ◽  
Dynamical Evolution ◽  
Stellar Systems ◽  
Internal Dynamics ◽  
Blue Stragglers ◽  
Blue Straggler ◽  
Specific Frequency ◽  
Definition Of

AbstractIn this paper I present an overview of the main observational properties of a special class of exotic objects (the so-called Blue Straggler Stars, BSSs) in Galactic Globular Clusters (GCs). The BSS specific frequency and their radial distribution are discussed in the framework of using this stellar population as probe of GC internal dynamics. In particular, the shape of the BSS radial distribution has been found to be a powerful tracer of the dynamical evolution of stellar systems, thus allowing the definition of an empirical “clock”able to measure the dynamical age of stellar aggregates from pure observational properties.

Binary evolution and double sequences of blue stragglers in globular clusters

2018 ◽  
Vol 14 (S343) ◽  
pp. 427-428
Author(s):  
Dengkai Jiang ◽  
Xuefei Chen ◽  
Lifang Li ◽  
Zhanwen Han
Keyword(s):  
Mass Transfer ◽  
Globular Clusters ◽  
Double Sequences ◽  
Single Star ◽  
Blue Stragglers ◽  
Blue Straggler ◽  
Magnitude Diagram ◽  
Blue Component ◽  
Binary Evolution ◽  
Red Sequence

AbstractBinary evolution can produce different blue-straggler binaries, for example, blue stragglers with a bright, red component, or with a faint, blue component. In globular clusters, these blue-straggler binaries are generally observed as a single star, because two components can not be distinguished. Therefore, these blue-straggler binaries can be located in different regions of the color-magnitude diagram of globular clusters, e.g. blue sequence and red sequence observed in M30. We suggest that binary evolution can contribute to the blue stragglers in both of the sequences. Some blue stragglers in the blue sequence may have a faint white dwarf companion, while the red sequence includes some binaries experiencing mass transfer. It should be noted that the red sequence may also have other binaries, for example, the binaries just finished the mass transfer, and the binaries including a blue straggler (the accretors) that have evolved away from the blue sequence.

scholarly journals Close binary evolution and blue straggler formation

2008 ◽  
Vol 4 (S252) ◽  
pp. 371-377
Author(s):  
P. Lu. ◽  
L. Deng
Keyword(s):  
Mass Transfer ◽  
Stellar Evolution ◽  
Close Binary ◽  
Close Binaries ◽  
Evolutionary Models ◽  
Mass Ratio ◽  
Blue Stragglers ◽  
Blue Straggler ◽  
Young Clusters ◽  
Binary Evolution

AbstractIn order to discuss the contribution of mass transfer in primordial close binaries to the blue straggler population in young clusters, we use Eggleton's stellar evolution code to simulate a grid of case A binary evolutionary models with the initial donor mass 2.0 – 8.0 M⊙ and mass ratio 0.1 – 0.9. The models cover the whole case A binaries that will experience mass transfer between 30.0 Myr to 1.0 Gyr. Based on such detailed models, we present a simulation to compare with the HST observation of young cluster NGC 1831 which can be fit with an isochrone of log(age) = 8.65. The results show very few blue stragglers could be produced by case A binary evolution. There must be some other mechanisms for blue straggler formation in young clusters.

scholarly journals Blue Stragglers: Spectra of Globular Clusters

2009 ◽  
Vol 5 (S262) ◽  
pp. 23-26
Author(s):  
A. J. Cenarro ◽  
J. L. Cervantes ◽  
M. A. Beasley ◽  
A. Marin-Franch ◽  
A. Vazdekis
Keyword(s):  
Globular Clusters ◽  
Stellar Population ◽  
Main Sequence ◽  
Stellar Systems ◽  
Blue Stragglers ◽  
Horizontal Branch Stars ◽  
Blue Straggler ◽  
Balmer Lines ◽  
Specific Frequency ◽  
High Metallicity

AbstractThe integrated Balmer lines of unresolved stellar systems have been widely used as age indicators, since they are sensitive to the temperature of the main sequence turn-off. However, the existence of “non-canonical” stellar stages such as hot horizontal branch stars and blue straggler stars (BSSs) can lead to underestimations of the true stellar population ages. Using an optimized Hβ index in conjunction with HST/WFPC2 color-magnitude diagrams (CMDs), we find that Galactic globular clusters of similar metallicity exhibit a large scatter in their Hβ strengths, which does not correlate with their CMD-derived ages. Instead, we demonstrate that the specific frequency of BSSs is responsible for the observed Hβ scatter at intermediate-to-high metallicity, in the sense that, at fixed metallicity, higher BSS ratios lead to larger integrated Hβ strengths. Therefore, the specific frequency of BSSs sets a fundamental limit on the accuracy for which integrated spectroscopic ages can be determined for globular clusters and, probably, other stellar systems like galaxies. The observational implications of this result are discussed.

Sign in / Sign up

Export Citation Format

Share Document