Different Characteristics of the Bright Branches of the Globular Clusters M3 and M13

Cho, Donghwan; Lee, Sang-Gak; Jeon, Young‐Beom; Sim, Kyung Jin

doi:10.1086/428369

Cited by 20 publications

(19 citation statements)

References 48 publications

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“…All observations of M53 and M92 were carried out using the 1.8 m telescope (f/8) and SITe 2048 × 2048 CCD camera at the Bohyunsan Optical Astronomy Observatory (BOAO) in Korea in the BV I bands on the same nights using the same instrumental setup, which was also the same as that used by Cho et al (2005). Details of the observations of M92 can be found in the report by Cho & Lee (2007).…”

Section: Observationsmentioning

confidence: 99%

“…Second, the asymptotic giant branch (AGB) is clearly separated in all three kinds of CMDs from the RGB sequence from ∼1.0 mag below the RGB tip down to the bottom of the AGB. On the other hand, the AGB bump (Ferraro et al 1999;Cassisi et al 2001), which indicates the clump of AGB stars at the beginning of He-shell burning, is difficult to identify because of the sparse distribution pattern of AGB stars in the CMDs compared to the AGB bumps of the GCs M3 (NGC 5272), M13 (NGC 6205), M15 (NGC 7078), and M92 (Cho et al 2005;Cho & Lee 2007). Finally, as reported by Rey et al (1998) and Beccari et al (2008), there are many BSSs that extend diagonally from the main sequence of M53, and the BSSs are delineated most clearly in the V versus B−I CMD due to about a factor of two higher color resolution than in the V versus B−V or V versus V − I CMD.…”

Section: Color-magnitude Diagramsmentioning

confidence: 99%

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Relative Age Difference Between the Metal-Poor Globular Clusters M53 and M92

Cho¹,

Sung²,

Lee³

et al. 2016

Journal of The Korean Astronomical Society

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CCD photometric observations of the globular cluster (GC), M53 (NGC 5024), are performed using the 1.8 m telescope at the Bohyunsan Optical Astronomy Observatory in Korea on the same nights (2002 April and 2003 May) as the observations of the GC M92 (NGC 6341) reported by Cho and Lee using the same instrumental setup. The data for M53 is reduced using the same method as used for M92 by Cho and Lee, including preprocessing, point-spread function fitting photometry, and standardization etc. Therefore, M53 and M92 are on the same photometric system defined by Landolt, and the photometry of M53 and M92 is tied together as closely as possible. After complete photometric reduction, the V versus B − V , V versus V − I, and V versus B − I color-magnitude diagrams (CMDs) of M53 are produced to derive the relative ages of M53 and M92 and derive the various characteristics of its CMDs in future analysis. From the present analysis, the relative ages of M53 and M92 are derived using the ∆(B − V ) method reported by VandenBerg et al. The relative age of M53 is found to be 1.6 ± 0.85 Gyr younger than that of M92 if the absolute age of M92 is taken to be 14 Gyr. This relative age difference between M53 and M92 causes slight differences in the horizontal-branch morphology of these two GCs.

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Section: Observationsmentioning

confidence: 99%

Section: Color-magnitude Diagramsmentioning

confidence: 99%

Relative Age Difference Between the Metal-Poor Globular Clusters M53 and M92

Cho¹,

Sung²,

Lee³

et al. 2016

Journal of The Korean Astronomical Society

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“…The analysis by Cho et al (2005) determined an observed value R 2 = 0.12 ± 0.03 for M 3 (we estimated the error bar on R 2 using Poisson statistics). The simulations by A81, page 6 of 8 Dalessandro et al (2013) match the observed stellar distribution and magnitude levels along the cluster HB with a range of initial Y abundances equal to ∼0.02, starting from a minimum Y = 0.246.…”

Section: Consistency Checksmentioning

confidence: 99%

“…Our HB simulations provide R 2 = 0.06 (as for NGC 6752) again in very good agreement with the observations. The study by Cho et al (2005) provides another very interesting test for the evolutionary timescales of the models. They determined R 2 = 0.16 ± 0.07 (we calculated the error bar from Poisson statistics) when considering all AGB stars but only the reddest component along the HB, e.g.…”

Section: Consistency Checksmentioning

confidence: 99%

On the missing second generation AGB stars in NGC 6752

Cassisi

Salaris

Pietrinferni

et al. 2014

A&A

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In recent years the view of Galactic globular clusters as simple stellar populations has changed dramatically, it is now thought that basically all globular clusters host multiple stellar populations, each with its own chemical abundance pattern and colour-magnitude diagram sequence. Recent spectroscopic observations of asymptotic giant branch stars in the globular cluster NGC 6752 have disclosed a low [Na/Fe] abundance for the whole sample, suggesting that they are all first generation stars, and that all second generation stars fail to reach the AGB in this cluster. A scenario proposed to explain these observations invokes strong mass loss in second generation horizontal branch stars -all located at the hot side of the blue and extended horizontal branch of this cluster -possibly induced by the metal enhancement associated to radiative levitation. This enhanced mass loss would prevent second generation stars from reaching the asymptotic giant branch phase, thus explaining at the same time the low value of the ratio between horizontal branch and asymptotic giant branch stars (the R 2 parameter) observed in NGC 6752. We have critically discussed this mass-loss scenario, finding that the required mass-loss rates are of the order of 10 −9 M yr −1 , significantly higher than current theoretical and empirical constraints. By making use of synthetic horizontal branch simulations, we demonstrate that our modelling correctly predicts the R 2 parameter for NGC 6752, without the need to invoke very efficient mass loss during the core He-burning stage. As a test of our stellar models we show that we can reproduce the observed value of R 2 for both M 3, a cluster of approximately the same metallicity and with a redder horizontal branch morphology, and M 13, a cluster with a horizontal branch very similar to NGC 6752. However, our simulations for the NGC 6752 horizontal branch predict however the presence of a significant fraction of second generation stars (about 50%) along the cluster asymptotic giant branch. We conclude that there is no simple explanation for the lack of second generation stars in the spectroscopically surveyed sample, although the interplay between mass loss (with low rates) and radiative levitation may play a role in explaining this puzzle.

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“…These theoretical LF represent the time spent in each bin of magnitude V by models on the RGB with magnitudes lower than V = 16.6. We chose this cut-off so as to compare the models' predictions with the observed luminosity function of the globular cluster M 13 as given by Cho et al (2005).…”

Section: Red Giant Branchmentioning

confidence: 99%

Rotational mixing in low-mass stars

Palacios¹,

Charbonnel

Talon

et al. 2006

A&A

205

235

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Aims. In this paper we study the effects of rotation in low-mass, low-metallicity RGB stars. Methods. We present the first evolutionary models taking into account self-consistently the latest prescriptions for the transport of angular momentum by meridional circulation and shear turbulence in stellar interiors as well as the associated mixing processes for chemicals computed from the ZAMS to the upper RGB. We discuss the uncertainties associated with the physical description of the rotational mixing in detail and carefully study their effects on the rotation profile, diffusion coefficients, structural evolution, lifetimes, and chemical signatures at the stellar surface. We focus in particular on the various assumptions concerning the rotation law in the convective envelope, the initial rotation velocity distribution, the presence of µ-gradients, and the treatment of the horizontal and vertical turbulence.Results. This exploration leads to two main conclusions. (1) After completion of the first dredge-up, the degree of differential rotation (and hence mixing) is maximised in the case of a differentially rotating convective envelope (i.e., j CE (r) = const.), as anticipated in previous studies. (2) Even with this assumption, and contrary to some previous claims, the present treatment for the evolution of the rotation profile and associated meridional circulation and shear turbulence does not lead to enough mixing of chemicals to explain the abundance anomalies in low-metallicity field and globular cluster RGB stars observed around the bump luminosity. Conclusions. This study raises questions that need to be addressed in the near future. These include, for example, the interaction between rotation and convection and the trigger of additional hydrodynamical instabilities.

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Different Characteristics of the Bright Branches of the Globular Clusters M3 and M13

Cited by 20 publications

References 48 publications

Relative Age Difference Between the Metal-Poor Globular Clusters M53 and M92

Relative Age Difference Between the Metal-Poor Globular Clusters M53 and M92

On the missing second generation AGB stars in NGC 6752

Rotational mixing in low-mass stars

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