Star-to-Star Abundance Variations among Bright Giants in the Mildly Metal-poor Globular Cluster M4

Ivans, Inese I.; Sneden, Christopher; Kraft, Robert P.; Suntzeff, Nicholas B.; Smith, Verne V.; Langer, G. E.; Fulbright, Jon P.

doi:10.1086/301017

Cited by 267 publications

(461 citation statements)

References 95 publications

(178 reference statements)

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“…The mean abundance ratios of Ba (see x 7.6 for details), La, and Eu are consistent with the earlier results of Ivans et al (2001) listed in Table 8. The abundances of Ba, La, and Eu are overabundant relative to Fe, as is seen in other globular clusters such as M4 (Ivans et al 1999) and M15 (Sneden et al 1997 Burris et al (2000), Ba is a neutron capture element synthesized through s-process reactions that occur mainly in low-mass asymptotic giant branch stars, while Eu is exclusively an r-process element.…”

Section: Neutron Capture Elementsmentioning

confidence: 68%

“…The dashed line corresponds to the anticorrelation observed in M4 from Ivans et al (1999), adopted here and in Ramírez & Cohen (2002) as a fiducial line. Our observed range in [Na/Fe] is similar to the range observed by these other studies, but our range in [O/Fe] is considerably smaller.…”

Section: Sodium and Oxygenmentioning

confidence: 97%

“…The open triangle represents the mean value for the main-sequence stars, whose [O/Fe] is obtained through the equivalent widths measured in the summed spectra and whose [Na/Fe] is the average of the values of the main-sequence stars derived individually. In view of the large sample of bright RGB stars studied in M4 by Ivans et al (1999), we adopt their results for the observed anticorrelation between Na and O among red giants in this cluster to provide a fiducial line for a visual comparison. The anticorrelation found from their sample is indicated as a dashed line in Figure 12.…”

Section: Sodium and Oxygenmentioning

confidence: 99%

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Abundances in Stars from the Red Giant Branch Tip to near the Main-Sequence Turnoff in M5

Ramírez

Cohen

2003

The Astronomical Journal

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We present the iron abundance and abundance ratios for 18 elements with respect to Fe in a sample of stars with a wide range in luminosity, from luminous giants to stars near the turnoff in the globular cluster M5. The analyzed spectra, obtained with the High Resolution Echelle Spectrograph at the Keck Observatory, are of high dispersion (R = /D = 35,000). We find that the neutron capture, the iron peak, and the -element abundance ratios show no trend with T eff and low scatter around the mean between the top of the red giant branch and near the main-sequence turnoff, suggesting that at this metallicity non-LTE effects are not important over the range of stellar parameters spanned by our sample. To within the precision of the measurements (about AE0.1 dex), gravitationally induced heavy-element diffusion does not appear to be present among the stars near the main-sequence turnoff studied here. Our work and other recent studies suggest that heavy-element diffusion is inhibited in the surface layers of metal-poor stars. Differences in the Na abundance from star to star that extend to the main-sequence turnoff are detected in our sample in M5. The anticorrelation between O and Na abundances, observed in other metal-poor globular clusters, is not detected in our sample, but it may be hidden among stars with only upper limits for their O abundances. As we found in M71, there is a hint of star-to-star variation in the Zr abundance. Overall the abundance ratios of M5 appear very similar to those of M71, with the possible exception of the neutron capture element Ba, for which we argue that the apparent difference may be due to difficulties in the analysis. As in M71, the -elements Mg, Ca, Si, and Ti are overabundant relative to Fe. The results of our abundance analysis of 25 stars in M5 provide further evidence of abundance variations among specific light elements at unexpectedly low luminosities, which cannot be explained by our current understanding of stellar evolution.

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Section: Neutron Capture Elementsmentioning

confidence: 68%

Section: Sodium and Oxygenmentioning

confidence: 97%

Section: Sodium and Oxygenmentioning

confidence: 99%

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Abundances in Stars from the Red Giant Branch Tip to near the Main-Sequence Turnoff in M5

Ramírez

Cohen

2003

The Astronomical Journal

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“…Spectroscopic studies of bright RGB stars in M 4, have shown significant star-to-star light-element abundance variations (Norris 1981;Gratton et al 1986;Brown & Wallerstein 1992;Drake et al 1992;Smith et al 2005), with sodium-oxygen and magnesium-aluminum correlations (Ivans et al 1999;Marino et al 2008;Villanova & Geisler 2011). High-resolution VLT/UVES spectra for about one hundred RGB stars revealed two groups of stars in the Na versus O plane.…”

Section: Multiple Stellar Populations Within Mmentioning

confidence: 99%

The M 4 Core Project with HST: I. Overview and first epoch

et al. 2013

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We present an overview of the ongoing Hubble Space Telescope large program GO-12911. The program is focused on the core of M 4, the nearest Galactic globular cluster, and the observations are designed to constrain the number of binaries with massive companions (black holes, neutron stars, or white dwarfs) by measuring the "wobble" of the luminous (mainsequence) companion around the center of mass of the pair, with an astrometric precision of ∼ 50 μas. The high spatial resolution and stable medium-band PSFs of WFC3/UVIS will make these measurements possible. In this work we describe (i) the motivation behind this study, (ii) our observing strategy, (iii) the many other investigations enabled by this unique data set, and which of those our team is conducting, and (iv) a preliminary reduction of the first-epoch dataset collected on

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“…Despite the importance of the C+N+O content in globular clusters, there is only a modest number of studies on this topic (e.g., Brown et al 1991;Dickens et al 1991;Ivans et al 1999;Cohen & Meléndez 2005;Smith et al 2005;Yong et al 2008b;Marino et al 2011Marino et al , 2012. For NGC 1851, there are conflicting results regarding the C+N+O abundance sum Villanova et al 2010).…”

Section: Introductionmentioning

confidence: 99%

CNO abundances in the globular clusters NGC 1851 and NGC 6752★

Yong¹,

Grundahl²,

Norris³

2014

Monthly Notices of the Royal Astronomical Society

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We measure the C+N+O abundance sum in red giant stars in two Galactic globular clusters, NGC 1851 and NGC 6752. NGC 1851 has a split subgiant branch which could be due to different ages or C+N+O content while NGC 6752 is representative of the least complex globular clusters. For NGC 1851 and NGC 6752, we obtain average values of A(C+N+O) = 8.16 ± 0.10 (σ = 0.34) and 7.62 ± 0.02 (σ = 0.06), respectively. When taking into account the measurement errors, we find a constant C+N+O abundance sum in NGC 6752. The C+N+O abundance dispersion is only 0.06 dex, and such a result requires that the source of the light element abundance variations does not increase the C+N+O sum in this cluster. For NGC 1851, we confirm a large spread in C+N+O. In this cluster, the anomalous RGB has a higher C+N+O content than the canonical RGB by a factor of four (∼0.6 dex). This result lends further support to the idea that the two subgiant branches in NGC 1851 are roughly coeval, but with different CNO abundances.

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Star-to-Star Abundance Variations among Bright Giants in the Mildly Metal-poor Globular Cluster M4

Cited by 267 publications

References 95 publications

Abundances in Stars from the Red Giant Branch Tip to near the Main-Sequence Turnoff in M5

Abundances in Stars from the Red Giant Branch Tip to near the Main-Sequence Turnoff in M5

The M 4 Core Project with HST: I. Overview and first epoch

CNO abundances in the globular clusters NGC 1851 and NGC 6752★

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