M92 (NGC 6341) Is a Metal-complex Globular Cluster with an Atypical Primordial Population

Lee, Jae Woo

doi:10.3847/2041-8213/acd05a

Cited by 5 publications

(13 citation statements)

References 39 publications

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“…In Figure 4, we show [C/Fe] ch and [N/Fe] nh against the V magnitude with and without the differential reddening correction, suggesting that the differential reddening correction does not significantly affect our photometric [C/Fe] ch and [N/Fe] nh . Our results clearly show that the carbon abundance decreases and nitrogen abundance increases in RGB stars brighter than the RGBB (V ≈14.0 mag for M22; Lee 2015) as can be seen in our previous studies of other Galactic GCs, M5, M3, and M92 (Lee 2021(Lee , 2023Lee & Sneden 2021).…”

Section: Metallicity Carbon and Nitrogen Abundancessupporting

confidence: 87%

“…We constructed 97 model atmospheres and synthetic spectra for each chemical composition from the lower main sequences to the tip of RGB sequences using ATLAS12 (Kurucz 2011) and the latest version of MOOGS-CAT (Sneden 1974;Sobeck et al 2011). As we discussed in our previous works (Lee & Sneden 2021;Lee 2023), the latest version of MOOGSCAT (Sobeck et al 2011) takes proper care of Rayleigh scattering from neutral hydrogen (RSNH) atoms with a nonlocal thermodynamic equilibrium treatment of the source function, which is important to calculate continuum opacities for our short-wavelength indices such as our JWL34 (i.e., nh JWL ), due to a λ −4 dependency of the RSNH cross section (see Lee & Sneden 2021, and references therein).…”

Section: Metallicity Carbon and Nitrogen Abundancesmentioning

confidence: 80%

“…The hk JWL index is a good photometric measure of metallicity, while the nh JWL , cn JWL , and ch JWL indices are measures of NH absorption band at λ3360, CN at λ3883, and CH at λ4250 Å, respectively (e.g., see Lee et al 2009;Lee 2015Lee , 2022Lee , 2023Lee & Sneden 2021).…”

Section: Photometric Indices and Color-magnitude Diagramsmentioning

confidence: 99%

“…We argue that different initial helium abundances between the FG and SG are responsible for the difference in the slopes. Due to the high helium abundances of the SG stars, which can be inferred from their RGBB V magnitudes (e.g., Lee 2020Lee , 2023Lee & Sneden 2021), the SG RGB stars have high temperature at the hydrogen burning shell, which causes slightly faster carbon destruction through the CN cycle (e.g., Church et al 2014).…”

Section: Surface Carbon Depletion Rates Of Milky Way Globularmentioning

confidence: 99%

“…During the past decade, we developed a new photometric system combined with the robust and self-consistent theoretical fine model grids with various parameter sets to simultaneously measure the key elements of GC MSPs, [Fe/H], [C/Fe], and [N/ Fe], even in the very crowded field, where traditional spectroscopic observations cannot be applied (Lee 2017(Lee , 2019(Lee , 2021(Lee , 2022(Lee , 2023Lee & Sneden 2021).…”

Section: Introductionmentioning

confidence: 99%

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Carbon Abundance of Globular Cluster M22 (NGC 6656) and the Surface Carbon Depletion Rates of the Milky Way Globular Clusters

Lee

2023

ApJL

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It is well known that metal-poor red giant branch (RGB) stars show variations in some elemental abundances, including carbon, due to the internal mixing accompanied by their own in situ CN cycle in the hydrogen burning shell. With our new photometric carbon abundance measurements of RGB stars in M22 and other globular clusters (GCs) in our previous studies, M5, M3, and M92, we derive the carbon depletion rates against the V magnitude, d[C/Fe]/M V , for individual populations in each GC. We find the metallicity dependence of the carbon depletion rates, d[C/Fe]/M V ∝ −0.25[Fe/H]. Our results also suggest that the carbon depletion rates of the second generation (SG) of stars are larger than those of the first generation (FG) of stars in our sample GCs, most likely due to different internal temperature profiles with different initial helium abundances between the FG and SG. Our results can provide critical constraints both on understanding the mixing efficiency in the theoretical models, which is largely unknown, and on interpretation of the observational carbon abundance evolution of the bright halo RGB stars.

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Section: Metallicity Carbon and Nitrogen Abundancessupporting

confidence: 87%

Section: Metallicity Carbon and Nitrogen Abundancesmentioning

confidence: 80%

Section: Photometric Indices and Color-magnitude Diagramsmentioning

confidence: 99%

Section: Surface Carbon Depletion Rates Of Milky Way Globularmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Carbon Abundance of Globular Cluster M22 (NGC 6656) and the Surface Carbon Depletion Rates of the Milky Way Globular Clusters

Lee

2023

ApJL

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MgAl burning chain in ω Centauri

Alvarez Garay,

Mucciarelli,

Bellazzini

et al. 2024

A&A

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In this study, we report the results of the analysis of Fe, Mg, Al, and Si abundances analysis for a sample of 439 stars in ω Centauri, using high-resolution spectra obtained with the VLT/FLAMES multi-object spectrograph. Our analysis reveals the presence of four distinct Fe populations, with the main peak occurring at a low metallicity, consistent with previous literature findings. We observe a discrete and pronounced Mg–Al anticorrelation, which exhibits variations in shape and extension as a function of metallicity. Specifically, this anticorrelation is present in stars with metallicities lower than approximately −1.3 dex, while it becomes less evident or absent for higher [Fe/H] values. Additionally, we detect (anti)correlations between Mg and Si, and between Al and Si, whose extensions also vary with metallicity, similar to the Mg–Al anticorrelation. These results suggest that the MgAl cycle plays a crucial role in the formation of multiple populations in ω Centauri, with the presence of all (anti)correlations at metallicities lower than –1.3 dex, providing evidence for the burning of Mg at very high temperatures (> 108 K), at least in the metal-poor regime. Furthermore, we observe a clear trend of stars with [Al/Fe] > +0.5 dex as a function of metallicity, confirming for the first time the existence of the two channels of Al production and destruction. This evidence can help to provide further constraints on the potential nature of the polluters responsible for the observed chemical anomalies in this stellar system. Finally, we find that the two most metal-poor populations identified in our sample are compatible with null or very small metallicity dispersion and we discuss how this result fits into a scenario where ω Centauri is the remnant of a disrupted nucleated dwarf galaxy.

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Benchmarking the effective temperature scale of red giant branch stellar models: The case of the metal-poor halo giant HD 122563

Creevey,

Cassisi,

Thévenin

et al. 2024

A&A

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There is plenty of evidence in the literature of significant discrepancies between the observations and models of metal-poor red giant branch stars, in particular regarding the effective temperature scale. We revisit the benchmark star HD\,122563 using the most recent observations from Data Release 3, to investigate if these new constraints may help in resolving this discrepancy. We review the most recent spectroscopic determinations of the metallicity Fe/H of HD\,122563, and provide a new assessment of its fundamental parameters, specifically, bolometric luminosity surface gravity, plus a photometric determination of its metal content. Using these constraints, we compare the position of the star in the Hertzsprung-Russell (H-R) diagram with various recent sets of stellar evolution tracks. The H-R diagram analysis reveals a significant disagreement between observed and theoretical values, when adopting the most recent spectroscopic estimate of Fe/H . On the other hand, by using the photometric determination of Fe/H some of the selected sets of stellar tracks appear in fair agreement with observations. The sets with discrepant can be made to agree with observations either by modifying the prescription adopted to calculate the models' outer boundary conditions, and/or by reducing the adopted value of the mixing length parameter with respect to the solar-calibration. A definitive assessment of whether the scale of metal-poor stellar red giant branch models is consistent with observations requires a more robust determination of the fundamental parameters of HD 122563 and also a larger sample of calibrators. From the theoretical side, it is crucial to minimise the current uncertainties in the treatment (boundary conditions, temperature gradient) of the outer layers of stellar models with convective envelopes.

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M92 (NGC 6341) Is a Metal-complex Globular Cluster with an Atypical Primordial Population

Cited by 5 publications

References 39 publications

Carbon Abundance of Globular Cluster M22 (NGC 6656) and the Surface Carbon Depletion Rates of the Milky Way Globular Clusters

Carbon Abundance of Globular Cluster M22 (NGC 6656) and the Surface Carbon Depletion Rates of the Milky Way Globular Clusters

MgAl burning chain in ω Centauri

Benchmarking the effective temperature scale of red giant branch stellar models: The case of the metal-poor halo giant HD 122563

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