Metal Abundances of Red Clump Stars in Open Clusters. I. NGC 6819

By A. Bragaglia, E. Carretta, R. Gratton, M. Tosi, G. Bonanno, P. Bruno, A. Calì, R. Claudi, R. Cosentino, S. Desidera and 3 more. 2000

146 citations recorded by the source corpus.

We present an analysis of high-dispersion spectra (R ∼ 40,000) of three red clump stars in the old open cluster NGC 6819. The spectra were obtained with SARG, the high-dispersion spectrograph of the Telescopio Nazionale Galileo. The spectra were analyzed using both equivalent widths measured with an automatic procedure and comparisons with synthetic spectra. NGC 6819 is found to be slightly metal-rich ([Fe/H] = +0.09 ± 0.03, internal error); there are no previous high-resolution studies to compare. Most element-to-element abundance ratios are close to solar; we find a slight excess of Si and a significant Na overabundance. Our spectra can also be used to derive the interstellar reddening toward the cluster by comparing the observed colors with those expected from line excitation: we derive E(B-V) = 0.14 ± 0.04, in agreement with the most recent estimate for this cluster.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/0460777ed6e2583dec070716abd48bb5cff30907

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In Astronomy and Astrophysics

1. R. Gratton
2. E. Carretta
3. A. Bragaglia
4. F. D’Antona
5. G. Piotto
6. Santi Cassisi
7. D. Stello
8. A. Karakas

In Instrumentation

1. F. D’Antona
2. R. Gratton
3. E. Carretta
4. A. Bragaglia
5. G. Piotto
6. D. Stello
7. P. Ventura
8. Santi Cassisi

Citations in the corpus

• Na-O Anticorrelation and HB. VII. The chemical composition of first and second-generation stars in 15 globular clusters from GIRAFFE spectra (2009, methodology): “Equivalent widths (EWs) were measured as described in detail in Bragaglia et al. (2001) with the same automatic procedure we used in the previous analysis of GIRAFFE spectra (Papers I, II, VI, V) for the definition of the local continuum around each line.”
• A Large Stellar Evolution Database for Population Synthesis Studies. I. Scaled Solar Models and Isochrones (2004, methodology): “We have adopted the recent ½Fe=H ¼ 0:09 0:03 determination by Bragaglia et al. (2001) and found a a successful fit with our ½Fe=H ¼ 0:06 isochrones for E(B V ) ¼ 0:14—in perfect agreement with the spectroscopic value E(B V ) ¼ 0:14 0:04 determined by Bragaglia et al. (2001)—and a distance modulus…”
• Abundances for metal-poor stars with accurate parallaxes , I. Basic data (2003, methodology): “Equivalent widths (EW s) on all these spectra were measured using an our own automatic procedure, that uses a gaussian fitting routine (see Bragaglia et al. 2001 for details).”
• Na-O anticorrelation and HB - VIII. Proton-capture elements and metallicities in 17 globular clusters from UVES spectra (2009, methodology): “Equivalent widths were measured with the same automatic procedure as we used in the analysis of GIRAFFE spectra (Papers I, II, VI, V, VII; see the detailed description in Bragaglia et al. 2001 for the definition of the local continuum around each line).”
• The Victoria-Regina Stellar Models: Evolutionary Tracks and Isochrones for a Wide Range in Mass and Metallicity that Allow for Empirically Constrained Amounts of Convective Core Overshooting (2005, methodology): “The reddening of NGC 6819 seems to be quite well established at E(B V )¼ 0:14 0:15mag (seeRosvick&VandenBerg 1998; Bragaglia et al. 2001), implying an apparent distance modulus of 12.35 if derived from a main-sequence fit of the photometry reported by Rosvick & VandenBerg to our models for ½Fe/H ¼…”
• The Initial-Final Mass Relation: Direct Constraints at the Low-Mass End (2007, methodology): “Using a similar analysis, Kalirai et al. (2001b) determined the reddening and distance modulus of NGC 6819 to be E(B − V ) ∼ 0.10 – 0.14 (see also Bragaglia et al. 2001) and (m − M)V = 12.30 ± 0.12.”
• NEW OPTICAL REDDENING MAPS OF THE LARGE AND SMALL MAGELLANIC CLOUDS (2011, methodology): “…each hot and each cool star in the field a reddening value is estimated, but we only use the data of the cool stars, which are much closer to the characteristics of the RC, with T ∼ 5000 K (Bragaglia et al. 2001) and RR Lyrae stars, with T ∼ 6500 K (Barcza 2010) at minimum light, used in our work.”
• Detailed abundances of a large sample of giant stars in M 54 and in the Sagittarius nucleus (2010, methodology): “Equivalent widths (EWs) were measured with the same semi-automatic procedure described in detail in Bragaglia et al. (2001), with a careful definition of the local continuum around each line, a crucial step at the limited resolution of our GIRAFFE spectra.”
• The Dawes Review 2: Nucleosynthesis and Stellar Yields of Low- and Intermediate-Mass Single Stars (2014, result): “But this is in contradiction with other studies showing typical overabundances of +0.5 (Bragaglia et al. 2001; Jacobson et al. 2007; Schuler et al. 2009).”
• Chemical abundance analysis of the open clusters Cr 110, NGC 2099 (M 37), NGC 2420, NGC 7789, and M 67 (NGC 2682) (2009, unknown): “…+0.12 Pace et al. (2008) +0.47 Carretta et al. (2007) M 11 +0.10 Gonzalez & Wallerstein (2000) +0.30 Boesgaard et al. (2009) M 34 +0.07 Schuler et al. (2003) NGC 6819 +0.09 Bragaglia et al. (2001) M 67 –0.03 Tautvaiŝiene (2000) NGC 6939 0.00 Jacobson et al.(2007) –0.01 Yong et al. (2005) NGC…”
• Asteroseismology of old open clusters with Kepler: direct estimate of the integrated red giant branch mass-loss in NGC 6791 and 6819 (2011, background): “NGC6819 is an open cluster of near-solar metallicity (Bragaglia et al. 2001) estimated to be 2-2.5 Gyr old (Kalirai & Tosi 2004; Basu et al. 2011).”
• Abundance Variations within Globular Clusters (2004, unknown): “…1996 NGC 2243 −0.48 2 Gratton & Contarini 1994 NGC 2264 −0.23 4 King et al. 2000 NGC 6705 or M11 +0.10 10 Gonzalez & Wallerstein 2000 NGC 6819 +0.09 3 Bragaglia et al. 2001 Mel 66 −0.38 2 Gratton & Contarini 1994 Mel 71 −0.30 2 Brown et al. 1996 because of the heterogeneity in the literature of…”
• Intrinsic iron spread and a new metallicity scale for globular clusters (2009, methodology): “Equivalent widths (EWs) were measured by an updated semi-automatic routine, in the package ROSA (Gratton 1988), using an homogeneous method for the continuum positioning (described in Bragaglia et al. 2001).”