A spectroscopic study of the blue stragglers in M67

We determined the cluster apex coordinates, studied the substructures and performed membership analysis in the central part (34 ′ ×33 ′ ) of the open cluster M 67. We used the individual stellar apexes method developed earlier and classical technique of proper motion diagrams in coordinate system connected with apex. The neighbour-to-neighbour distance technique was applied to detect space details. The membership list was corrected and some stars were excluded from the most probable members list. The apex coordinates have been determined as: A 0 = 132.97• ±0.81• and D 0 = 11.85 • ±0.90• . The 2D-space star density field was analysed and high degree of inhomogeneity was found.

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“…4). Liu et al (2008) and Pribulla et al (2008) have shown that these stars are blue stragglers. On this basis, we do not reject their membership.…”

Section: The Apex Determinationmentioning

confidence: 98%

Apex determination and detection of stellar clumps in the open cluster M 67

et al. 2014

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“…The flux of the BSS spectrum is then calibrated using the BSS's absolute magnitude and, finally, the spectrum of the BSS population is obtained by adding up all flux-calibrated BSS spectra, i.e., The approximation to use the spectra of single MS stars to represent the spectra of BSSs is made based on both theoretical (e.g., [3,4]) and observational (e.g., [23,32]) considerations. The major formation scenarios of BSSs, such as mergers of primordial binaries and dynamical encounters between stars, can replenish fresh hydrogen fuel in the core and rejuvenate BSSs to the MS stage.…”

Section: Building the Empirical Ssp Librarymentioning

confidence: 99%

Blue Stragglers in Clusters and Integrated Spectral Properties of Stellar Populations

Xin

Deng

2014

Ecology of Blue Straggler Stars

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Evolutionary population synthesis (EPS) has been widely used as a powerful tool to study the stellar contents of galaxies. In essence, EPS compares the observed, integrated spectrum of a galaxy with a combination of spectra of simple stellar populations (SSPs; single-age, single-metallicity populations) of different ages and metallicities, and decomposes the complex stellar contents into SSPs of known ages and metallicities to infer the galaxy's star-formation history. Over the past two decades, much work has been done to improve the accuracy of EPS and SSP models in various contexts (e.g., [6,7,19,34,35,36]).Unfortunately, population synthesis models still suffer from a number of limitations. One is our poor understanding of some advanced single-star evolutionary phases, such as of supergiants and asymptotic giant branch stars [41], while a second is an absence in the models of the results of stellar interactions, such as the so-called "stragglers" formed through mass transfer in binaries or stellar collisions. Such stars are usually very bright and can strongly affect the integrated-light properties of the entire system. The potential uncertainties inherent to EPS caused by ignoring these components could be much larger than those still remaining and due to the variety of input physics among different models.In this chapter, we focus on the second limitation to the standard SSP models. With the updated knowledge of stars, in particular on the physical properties of binary and collisional interactions that eventually create the exotic blue straggler stars (BSSs) discussed in previous chapters in this book, a more realistic prescription of stellar populations is now possible. The goal of this chapter is to present a new set of SSP models which include contributions from BSSs.

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“…Benz & Hills 1987, 1992) and observational (e.g. Shetrone & Sandquist 2000; Liu et al 2008) considerations. The major formation scenarios of BSs, such as mergers of primordial binaries and dynamical encounters between stars, can replenish fresh hydrogen fuel in the core and rejuvenate BSs to the MS stage.…”

Section: Bs‐ssp Modelsmentioning

confidence: 99%

“…The major formation scenarios of BSs, such as mergers of primordial binaries and dynamical encounters between stars, can replenish fresh hydrogen fuel in the core and rejuvenate BSs to the MS stage. Liu et al (2008) studied the spectral properties of a complete sample of 24 BSs in the Galactic OC NGC 2682 (M67) based on spectroscopic observations with a resolution of 3.2 Å pixel −1 and covering wavelengths of 3600–6900 Å. They concluded that BS spectra can be well represented by the theoretical spectra of single stars, at least at medium resolution. We use BC03 models to represent the spectrum of the population of normal member stars in an SSP (i.e.…”

Section: Bs‐ssp Modelsmentioning

confidence: 99%

Simple stellar population models including blue stragglers

Xin

Deng

Grijs

et al. 2010

Monthly Notices of the Royal Astronomical Society

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Observations show that nearly all star clusters and stellar populations contain blue straggler stars (BSs). BSs in a cluster can significantly enhance the integrated spectrum of the host population, preferentially at short wavelengths, and render it much bluer in photometric colours. Current theoretical simple stellar population (SSP) models constructed within the traditional framework of single and binary stellar evolution cannot fully account for the impact of these objects on the integrated spectral properties of stellar populations. Using conventional SSP models without taking into account BS contributions may significantly underestimate a cluster's age and/or metallicity, simply because one has to balance the observed bluer colours (or a bluer spectrum) with a younger age and/or a lower metallicity. Therefore, inclusion of BS contributions in SSP models is an important and necessary improvement for population synthesis and its applications. Here, we present a new set of SSP models, which include BS contributions based on our analysis of individual star clusters. The models cover the wavelength range from 91~{\AA} to 160~$\mu$m, ages from 0.1 to 20 Gyr and metallicities $Z=0.0004, 0.004, 0.008, 0.02$ (solar) and 0.05. We use the observed integrated spectra of several Magellanic Cloud star clusters to cross-check and validate our models. The results show that the age predictions from our models are closer to those from isochrone fitting in the clusters' colour-magnitude diagrams compared to age predictions based on standard SSP models.Comment: 16 pages, 15 figures, 4 tables, accepted for publication in MNRA

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A spectroscopic study of the blue stragglers in M67

Cited by 14 publications

References 42 publications

Apex determination and detection of stellar clumps in the open cluster M 67

Apex determination and detection of stellar clumps in the open cluster M 67

Blue Stragglers in Clusters and Integrated Spectral Properties of Stellar Populations

Simple stellar population models including blue stragglers

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