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 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 Star clusters as laboratories for stellar and dynamical evolution

2010 ◽  
Vol 368 (1913) ◽  
pp. 755-782 ◽  
Author(s):  
Jason S. Kalirai ◽  
Harvey B. Richer
Keyword(s):  
Mass Loss ◽  
Stellar Evolution ◽  
First Generation ◽  
Main Sequence ◽  
Star Clusters ◽  
Dynamical Evolution ◽  
Stellar Populations ◽  
Stellar Mass ◽  
Theoretical Studies ◽  
Chemical Enrichment

Open and globular star clusters have served as benchmarks for the study of stellar evolution owing to their supposed nature as simple stellar populations of the same age and metallicity. After a brief review of some of the pioneering work that established the importance of imaging stars in these systems, we focus on several recent studies that have challenged our fundamental picture of star clusters. These new studies indicate that star clusters can very well harbour multiple stellar populations, possibly formed through self-enrichment processes from the first-generation stars that evolved through post-main-sequence evolutionary phases. Correctly interpreting stellar evolution in such systems is tied to our understanding of both chemical-enrichment mechanisms, including stellar mass loss along the giant branches, and the dynamical state of the cluster. We illustrate recent imaging, spectroscopic and theoretical studies that have begun to shed new light on the evolutionary processes that occur within star clusters.

scholarly journals Stellar Populations in Star Clusters: The Role Played by Stochastic Effects

2002 ◽  
Vol 207 ◽  
pp. 616-624 ◽  
Author(s):  
Gustavo Bruzual A.
Keyword(s):  
Stellar Evolution ◽  
Ad Hoc ◽  
Star Clusters ◽  
Stellar Populations ◽  
Evolution Theory ◽  
Agb Stars ◽  
Population Synthesis ◽  
Stochastic Effects

In this paper I combine the results of a set of population synthesis models with simple Montecarlo simulations of stochastic effects in the number of stars occupying sparsely populated stellar evolutionary phases, to show that the scatter observed in the magnitudes and colors of LMC and NGC 7252 star clusters can be understood in the framework of current stellar evolution theory, without the need to introduce ad-hoc corrections (e.g. artificially increasing the number of AGB stars).

scholarly journals The stellar populations of low-luminosity active galactic nuclei - III. Spatially resolved spectral properties

2005 ◽  
Vol 356 (1) ◽  
pp. 270-294 ◽  
Author(s):  
R. Cid Fernandes ◽  
R. M. Gonzalez Delgado ◽  
T. Storchi-Bergmann ◽  
L. P. Martins ◽  
H. Schmitt
Keyword(s):  
Active Galactic Nuclei ◽  
Spectral Properties ◽  
Galactic Nuclei ◽  
Stellar Populations ◽  
Spatially Resolved

scholarly journals Modeling of Integrated Spectral Energy Distributions of Stellar Populations with Various Binary Fractions

2021 ◽  
Vol 2068 (1) ◽  
pp. 012048
Author(s):  
Zhongmu Li ◽  
Chen Yan
Keyword(s):  
Binary Stars ◽  
Star Clusters ◽  
Stellar Populations ◽  
Spectral Studies ◽  
Spectral Energy ◽  
Spectral Energy Distributions ◽  
Energy Distributions ◽  
Spectral Fitting ◽  
The Universe

Abstract Binary stars are common in the universe, but binary fractions are various in different star clusters and galaxies. Studies have shown that binary fraction affects the integrated spectral energy distributions obviously, in particular in the UV band. It affects spectral fitting of many star clusters and galaxies significantly. However, previous works usually take a fixed binary fraction, i.e., 0.5, and this is far from getting accurate results. Therefore, it is important to model the integrated spectral energy distributions of stellar populations with various binary fractions. This work presents a modeling of spectral energy distributions of simple stellar populations with binary fractions of 0.3, 0.7, and 1.0. The results are useful for different kinds of spectral studies.

scholarly journals On the precision of full-spectrum fitting of simple stellar populations – I. Well-sampled populations

2020 ◽  
Vol 498 (2) ◽  
pp. 2814-2832
Author(s):  
Randa Asa’d ◽  
Paul Goudfrooij
Keyword(s):  
Random Noise ◽  
Star Clusters ◽  
Stellar Populations ◽  
Asymptotic Giant Branch ◽  
Full Spectrum ◽  
Red Giant ◽  
Set Up ◽  
Age Range ◽  
Spectrum Fitting ◽  
Giant Branch Stars

ABSTRACT We investigate the precision of the ages and metallicities of 21 000 mock simple stellar populations (SSPs) determined through full-spectrum fitting. The mock SSPs cover an age range of 6.8 < log (age/yr) < 10.2, for three wavelength ranges in the optical regime, using both Padova and MIST isochrone models. Random noise is added to the model spectra to achieve S/N ratios between 10 and 100 per wavelength pixel. We find that for S/N ≥ 50, this technique can yield ages of SSPs to an overall precision of ∆log (age/yr)∼01 for ages in the ranges 7.0 ≤ log (age/yr) ≤ 8.3 and 8.9 ≤ log (age/yr) ≤ 9.4. For the age ranges of 8.3 ≤ log (age/yr) ≤ 8.9 and log (age/yr) ≥ 9.5, which have significant flux contributions from asymptotic giant branch and red giant branch stars, respectively, the age uncertainty rises to about ±0.3 dex. The precision of age and metallicity estimation using this method depends significantly on the S/N and the wavelength range used in the fitting. We quantify the systematic differences in age predicted by the MIST and Padova isochrone models, due to their different assumptions about stellar physics in various important (i.e. luminous) phases of stellar evolution, which needs to be taken in consideration when comparing ages of star clusters obtained using these popular models. Knowing the strengths and limitations of this technique is crucial in interpreting the results obtained for real star clusters and for deciding the optimal instrument set-up before performing the observations.

scholarly journals On Some Peculiar Features in the Sequences of the Old Open Star Clusters

1974 ◽  
Vol 59 ◽  
pp. 109-111
Author(s):  
A. Maeder
Keyword(s):  
Chemical Composition ◽  
Stellar Evolution ◽  
Main Sequence ◽  
Star Clusters ◽  
Open Star Clusters ◽  
Hydrogen Burning ◽  
The Core ◽  
Open Star ◽  
Solar Type ◽  
Good Agreement

In spite of the rather good agreement between the theory of stellar evolution and the observations, there exist some difficulties when one compares closely the sequences of open star clusters and the theoretical isochrones. Several, if not all, of the old open star clusters seem to be concerned, especially those which are accurately measured, namely Praesepe, NGC 2360, 752, 3680 and M67. The problem concerns the gap occuring in the HR diagram at the end of the phase of hydrogen burning in the core; it corresponds to the phase of hydrogen exhaustion (or of overall contraction). The sequence of M67 has been studied by Racine (1971) and Torres-Peimbert (1971). The well apparent gap is located farther from the zero-age main sequence than indicated by the models and the hook towards a larger Teff predicted during this phase is not observed. Differences in chemical composition may not be held responsible for these anomalies. From Torres-Peimbert's models, it may be assumed that neither solar type, nor super metal rich composition are able to reduce the discrepancies. As a further illustration, let us mention the case of NGC 752. In Table I, the main features related to the gap are examined: the disagreement, like in M67, essentially concern features 1 and 2. The observations are based on a recent study of Grenon and Mermillod (1973) and on Bell's data (1972). Bell has also mentioned the existence of discrepancies. As in M67, the gap is too far from the zero-age main sequence and does not present any sudden turning towards a larger Teff.

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