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 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 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 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 Homogeneous photometry of globular clusters—a progress report

2008 ◽  
Vol 4 (S258) ◽  
pp. 197-208
Author(s):  
Peter B. Stetson
Keyword(s):  
Stellar Evolution ◽  
Globular Clusters ◽  
Broad Band ◽  
Star Clusters ◽  
Theoretical Models ◽  
Progress Report

AbstractClassical broad-band photometry can provide direct comparisons of star clusters both with each other and with theoretical models of stellar evolution. The confidence with which conclusions can be drawn is often limited by the accuracy of the measurements. The present work is part of a long-term attempt to improve photometric calibrations.

scholarly journals Flare Stars in Star Clusters and Associations

1975 ◽  
Vol 67 ◽  
pp. 1-14 ◽  
Author(s):  
V. A. Ambartsumian ◽  
L. V. Mirzoyan
Keyword(s):  
Stellar Evolution ◽  
Star Clusters ◽  
Open Clusters ◽  
Point Of View ◽  
Flare Activity ◽  
Theoretical Point ◽  
Star Clusters And Associations ◽  
Stellar Flare ◽  
Dwarf Stars ◽  
Flare Stars

The study of stellar evolution can be undertaken either from a purely theoretical point of view or from a more observational approach. The present standpoint is the second one. It starts from the concepts of stellar evolution in associations and open clusters and from stellar flare activity. Statistical considerations show that flare activity is a regular stage in the evolution of stars through which all the dwarf stars go.

scholarly journals Magellanic globulars as cosmological tools

1991 ◽  
Vol 148 ◽  
pp. 165-169
Author(s):  
Alvio Renzini
Keyword(s):  
Galaxy Formation ◽  
Stellar Evolution ◽  
Globular Clusters ◽  
Star Clusters ◽  
Dynamical Evolution ◽  
Mass Range ◽  
Magellanic Clouds ◽  
Evolution Theory ◽  
Mass Functions ◽  
The Ideal

The globular clusters (GC) of the Magellanic Clouds play a very important role for many astrophysical and cosmological topics. For example, they represent the ideal testground for stellar evolution theory, they allow us to study the the early dynamical evolution of star clusters, to obtain accurate initial mass functions in a fairly extended mass range, to calibrate the Cepheid period-luminosity relation, and so on. In this brief paper I will touch upon two items which are of considerable cosmological interest, and about which Magellanic Cloud globulars provide unique information. These topics concern i) GC formation in galaxies, and ii) the epoch of galaxy formation.

scholarly journals Star clusters and single stellar populations

2009 ◽  
Vol 5 (S266) ◽  
pp. 304-311
Author(s):  
Licai Deng ◽  
Yu Xin
Keyword(s):  
Stellar Evolution ◽  
Spectral Properties ◽  
Star Clusters ◽  
Stellar Populations ◽  
Current Theory ◽  
Binary Interaction ◽  
Interaction Theory ◽  
Blue Stragglers ◽  
Evolutionary Scenario

AbstractStar clusters are ideal laboratories to test the theory of stellar evolution and provide very tight constraints on the concept of single stellar poputions (SSPs). Observations show that some stars fail to conform to the theoretical evolutionary scenario applicable to single stars. These special objects, particularly blue stragglers, present a challenge to our current theory of stellar evolution. They may be very important in the context of the integrated spectral properties of clusters. Here, we review the construction of SSP models, both empirically using star clusters and theoretically based on binary-interaction theory.

scholarly journals Spatially Resolving the Star Formation Histories of Three Nearby Nuclear Star Clusters

2021 ◽  
Vol 162 (6) ◽  
pp. 281
Author(s):  
Christian H. Hannah ◽  
Anil C. Seth ◽  
Dieu D. Nguyen ◽  
Antoine Dumont ◽  
Nikolay Kacharov ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Stellar Population ◽  
Star Clusters ◽  
Formation Mechanisms ◽  
Full Spectrum ◽  
Spatially Resolved ◽  
Open Question ◽  
Star Formation Histories ◽  
Spectrum Fitting

Abstract The formation of nuclear star clusters (NSCs) remains an open question. In this work, we use spatially-resolved HST/STIS spectroscopic observations of three nearby NSCs (hosted by NGC 5102, NGC 5206, and NGC 205) to constrain their formation histories by exploring radial variations of the stellar populations within each cluster. Utilizing full-spectrum fitting, we find substantial age and metallicity gradients within the central 0.″9 (16 pc) of the NSC in NGC 5102 where populations near the center are young/metal-rich (age ∼400 Myr and [M/H] ∼ −0.4) and become older/metal-poor at larger radii (mean age ∼1 Gyr and mean [M/H] ∼ −1.6 in the radial range [0.″3, 0.″9]). This behavior suggests that the young/metal-rich population at the center was formed from a period of in situ formation, while the older/metal-poor populations were likely formed by inspiraled globular clusters. The two broad populations observed in the NGC 5102 NSC (young/metal-rich and old/metal-poor) appear to be linked to the transition between the two morphological components of the NSC derived from the surface-brightness profile in Nguyen et al. (2018). The radial ranges explored in NGC 5206 and NGC 205 were much smaller due to poor data quality; in NGC 5206 we find a similar metallicity gradient to NGC 5102 (but with much lower significance), while the data for NGC 205 is too poor to reach any conclusions. Overall, this data highlights the links between the morphological and stellar population complexity of NSCs and their formation mechanisms.

scholarly journals Gaia Data Release 2

2018 ◽  
Vol 616 ◽  
pp. A10 ◽  
Author(s):  
◽  
C. Babusiaux ◽  
F. van Leeuwen ◽  
M. A. Barstow ◽  
C. Jordi ◽  
...  
Keyword(s):  
Stellar Evolution ◽  
White Dwarfs ◽  
Stellar Population ◽  
Open Clusters ◽  
Data Release ◽  
Low Mass ◽  
Different Populations ◽  
Fine Structures ◽  
First Time ◽  
Late Stages

Context. Gaia Data Release 2 provides high-precision astrometry and three-band photometry for about 1.3 billion sources over the full sky. The precision, accuracy, and homogeneity of both astrometry and photometry are unprecedented. Aims. We highlight the power of the Gaia DR2 in studying many fine structures of the Hertzsprung-Russell diagram (HRD). Gaia allows us to present many different HRDs, depending in particular on stellar population selections. We do not aim here for completeness in terms of types of stars or stellar evolutionary aspects. Instead, we have chosen several illustrative examples. Methods. We describe some of the selections that can be made in Gaia DR2 to highlight the main structures of the Gaia HRDs. We select both field and cluster (open and globular) stars, compare the observations with previous classifications and with stellar evolutionary tracks, and we present variations of the Gaia HRD with age, metallicity, and kinematics. Late stages of stellar evolution such as hot subdwarfs, post-AGB stars, planetary nebulae, and white dwarfs are also analysed, as well as low-mass brown dwarf objects. Results. The Gaia HRDs are unprecedented in both precision and coverage of the various Milky Way stellar populations and stellar evolutionary phases. Many fine structures of the HRDs are presented. The clear split of the white dwarf sequence into hydrogen and helium white dwarfs is presented for the first time in an HRD. The relation between kinematics and the HRD is nicely illustrated. Two different populations in a classical kinematic selection of the halo are unambiguously identified in the HRD. Membership and mean parameters for a selected list of open clusters are provided. They allow drawing very detailed cluster sequences, highlighting fine structures, and providing extremely precise empirical isochrones that will lead to more insight in stellar physics. Conclusions. Gaia DR2 demonstrates the potential of combining precise astrometry and photometry for large samples for studies in stellar evolution and stellar population and opens an entire new area for HRD-based studies.

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