C++—The Forgotten Trojan Horse

Johnson, E. Elizabeth

doi:10.1007/978-1-4302-0038-3_17

Cited by 6 publications

(12 citation statements)

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“…Carretta et al (2010) quantify the extension of the Na-O anti-correlation by looking at the interquartile range (IQR) of the [O/Na] values for each cluster; more extended anti-correlations have a higher IQR([O/Na]). Based on Na and O measurements compiled from various sources by Smith & Briley (2006) and measured by Johnson & Pilachowski (2012) for M13, and Carretta et al (2009a,b) for M10, we find that M13 has an IQR([O/Na]) of 0.70 compared to 0.56 for M10. Carretta et al (2010) also find that the IQR([O/Na]) correlates with the maximum temperature reached on the horizontal branch.…”

Section: Comparison To Other Clustersmentioning

confidence: 50%

“…Subsequent dynamical evolution will gradually erase these initial differences in the spatial distribution (see e.g., Vesperini et al 2013) eventually leading to the complete spatial mixing of the two populations. Depending on the cluster's evolutionary phase some memory of the initial spatial distribution of the two populations might be preserved and indeed in several clusters (see e.g., Bellini et al 2009;Lardo et al 2011;Carretta et al 2010;Johnson & Pilachowski 2012;Milone et al 2012;Cordero et al 2014;Simioni et al 2016) second generation stars have been found to be more centrally concentrated than first generation stars. Vesperini et al (2013) have found that in order to reach complete spatial mixing a cluster must be in its advanced evolutionary stage and have lost at least 60-70 % of its initial mass due to the effects of two-body relaxation (see also Miholics et al 2015).…”

Section: Spatial Distribution Of Multiple Populationsmentioning

confidence: 99%

“…One piece of evidence for a higher He abundance in M13 is the difference in the Na-O anti-correlation based on data from Carretta et al (2009a,b), Johnson & Pilachowski (2012), and Smith & Briley (2006). While both M10 and M13 show an anti-correlation in Na-O as expected, the anti-correlation is more extended in M13 than in M10.…”

Section: Comparison To Other Clustersmentioning

confidence: 99%

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Light Element Abundances and Multiple Populations in M10

Gerber¹,

Friel²,

Vesperini³

2018

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We present CN and CH band measurements for 137 RGB and AGB stars in the Galactic globular cluster M10. Our measurements come from low resolution spectroscopy taken with the Hydra spectrograph on the WIYN-3.5m telescope. We use these measurements to identify two populations of stars within the cluster, a CN-normal and CN-enhanced, and find that in our sample 60% of stars are CN-enhanced. Our large sample allows us to conduct a detailed analysis on the carbon and nitrogen abundances and the radial distribution of each population separately. Our analysis of the radial dependence shows that each population has the same radial distribution in the cluster, which is likely due to the cluster being dynamically evolved. We also compare our results to other methods of classifying multiple populations in globular clusters such as the Na-O anti-correlation and the HST pseudo-color magnitude diagrams. We find that these three methods of identifying multiple populations are in good agreement with each other for M10 and all lead to an estimate of the fraction of second generation stars approximately equal to 60%. Among AGB stars, when classified by the CN band, there appears to be a lack of second generation stars when compared to the RGB stars. However, when classified by [N/Fe], we find a similar 60% of AGB stars in the second generation. Finally, we use the measured carbon and nitrogen abundances in RGB stars to study the change of each element with magnitude as stars evolve up the RGB, comparing the results to globular clusters of similar metallicity, M3 and M13.

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Section: Comparison To Other Clustersmentioning

confidence: 50%

Section: Spatial Distribution Of Multiple Populationsmentioning

confidence: 99%

Section: Comparison To Other Clustersmentioning

confidence: 99%

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Light Element Abundances and Multiple Populations in M10

Gerber¹,

Friel²,

Vesperini³

2018

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“…Due to the role of the CO molecule in setting molecular equilibrium abundances in red giant photospheres, the [O/Fe] abundance used in generating the synthetic spectra for each star is an important constraint. Whenever possible, we used the literature values for any star in our study with measured [O/Fe] abundances Cohen & Melendez 2005;Carretta et al 2009a,b;Johnson & Pilachowski 2012;Boberg et al 2015Boberg et al , 2016Rojas-Arriagada et al 2016;Villanova et al 2016;Marino et al 2018). If a star did not have a direct measurement, but belonged to a cluster with other [O/Fe] measurements, we assigned an [O/Fe] equal to the cluster average for that star.…”

Section: Discussionmentioning

confidence: 99%

Carbon Abundance Inhomogeneities and Deep Mixing Rates in Galactic Globular Clusters

Gerber

Briley

Smith

2019

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Among stars in Galactic globular clusters the carbon abundance tends to decrease with increasing luminosity on the upper red giant branch, particularly within the lowest metallicity clusters. While such a phenomena is not predicted by canonical models of stellar interiors and evolution, it is widely held to be the result of some extra mixing operating during red giant branch ascent which transports material exposed to the CN(O)-cycle across the radiative zone in the stellar interior and into the base of the convective envelope, whereupon it is brought rapidly to the stellar surface.Here we present measurements of [C/Fe] abundances among 67 red giants in 19 globular clusters within the Milky Way. Building on the work of Martell et al., we have concentrated on giants with absolute magnitudes of M V ∼ −1.5 within clusters encompassing a range of metallicity (-2.4 < [Fe/H] < -0.3). The Kitt Peak National Observatory (KPNO) 4 m and Southern Astrophysical Research (SOAR) 4.1 m telescopes were used to obtain spectra covering the λ4300 CH and λ3883 CN bands. The CH absorption features in these spectra have been analyzed via synthetic spectra in order to obtain [C/Fe] abundances. These abundances and the luminosities of the observed stars were used to infer the rate at which C abundances change with time during upper red giant branch evolution (i.e., the mixing efficiency). By establishing rates over a range of metallicity, the dependence of deep mixing on metallicity is explored. We find that the inferred carbon depletion rate decreases as a function of metallicity, although our results are dependent on the initial [C/Fe] composition assumed for each star.

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“…For comparison, 47 Tuc, a cluster with a similar age and metallicity, has a much younger dynamical age of t/t rh ∼ 3 (using t rh value from Harris 1996Harris , 2010 and is observed to have a more centrally concentrated second generation compared to the first generation (Milone et al 2012;Cordero et al 2015). Other examples of clusters with more concentrated second generation stars can be found in Bellini et al (2009), Lardo et al (2011), Carretta et al (2010, Johnson & Pilachowski (2012), Milone et al (2012), and Simioni et al (2016). Clusters in which second generation stars are still more concentrated than first generation stars tend to be, in general, dynamically younger (see e.g.…”

Section: Distribution Across the Clustermentioning

confidence: 96%

Identifying Multiple Populations in M71 Using CN

Gerber

Friel

Vesperini

2020

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We have observed the CN features at ∼3800Å and 4120Å as well as the CH band at ∼4300Å for 145 evolved stars in the Galactic globular cluster M71 using the multi-object spectrograph, Hydra, on the WIYN-3.5m telescope. We use these measurements to create two δCN indices finding that both distributions are best fit by two populations, a CN-enhanced and CN-normal. We find that 42 ± 4% of the RGB stars in our sample are CN-enhanced. The percentage of CN-enhanced is 40 ± 13% for the AGB and 33 ± 9% for the HB stars, which suggests there are no missing second generation stars at these stages of stellar evolution. The two generations also separate in magnitude and color on the HB, which allows us to find the difference in He abundance between the two populations by fitting appropriate ZAHBs. The broad range of distances from the cluster's center covered by our sample allows us to study the dependence of the ratio of the number of first to second population stars on the distance from the cluster's center, and we find that this ratio does not vary radially and that the two populations are spatially mixed. Finally, we compare our identification of multiple populations with the classification based on the Na-O anti-correlation and the HST UV photometry, and we find good agreement with both methods.

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C++—The Forgotten Trojan Horse

Cited by 6 publications

References 0 publications

Light Element Abundances and Multiple Populations in M10

Light Element Abundances and Multiple Populations in M10

Carbon Abundance Inhomogeneities and Deep Mixing Rates in Galactic Globular Clusters

Identifying Multiple Populations in M71 Using CN

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