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J/A+A/455/271     Abundances of red giants in NGC 6441          (Gratton+, 2006)

Na-O anticorrelation and HB. III. The abundances of NGC 6441 from FLAMES-UVES spectra. Gratton R.G., Lucatello S., Bragaglia A., Carretta E., Momany Y., Pancino E., Valenti E. <Astron. Astrophys. 455, 271 (2006)> =2006A&A...455..271G
ADC_Keywords: Clusters, globular ; Stars, giant ; Equivalent widths ; Abundances, peculiar Keywords: stars: abundances - stars: atmospheres - stars: Population II - Galaxy: globular clusters: general - Galaxy: globular clusters: individual: NGC 6441 Abstract: The aim of the present work is to determine accurate metallicities for a group of red giant branch stars in the field of the bulge Globular Cluster NGC 6441. This is the third paper in a series resulting from a large project aimed at determining the extent of the Na-O anticorrelation among Globular Cluster stars and exploring its relationship with HB morphology. We present an LTE abundance analysis of these objects, based on data gathered with the FLAMES fiber facility and the UVES spectrograph at VLT2. Results. Five of the thirteen stars observed are members of the cluster. The average Fe abundance for these five stars is [Fe/H]=-0.39±0.04±0.05dex, where the first error bar includes the uncertainties related to star-to-star random errors, and the second one the systematic effects related to the various assumptions made in the analysis.The overall abundance pattern is quite typical of Globular Clusters, with an excess of the alpha-elements and of Eu. There is evidence that the stars of NGC 6441 are enriched in Na and Al, while they have been depleted of O and Mg by H-burning at high temperatures, analogous with extensive observations of other Globular Clusters: in particular, one star is clearly Na and Al-rich and O and Mg-poor. We also obtained quite high V abundances, but it is possible that this is an artifact of the analysis, since similar high V abundances are also derived for the field stars. These last are all more metal-rich than NGC 6441 and probably belong to the bulge population bulge. Description: Equivalent widths for 5 giants members of the globular cluster NGC6441 (Table 3) and 7 field giants (Table 4) File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 80 13 Photometry and spectroscopic data for stars observed with UVES table3.dat 43 800 Equivalent Widths for the cluster members table4.dat 43 1183 Equivalent Widths for field stars
See also: J/AJ/117/1313 : NGC 6441 VI photometry (Layden+, 1999) J/A+A/440/901 : Reddening and metallicity of NGC 6752 (Gratton, 2005) J/A+AS/113/299 : Abundances and velocities for cluster giants (Minniti 1995) J/AJ/127/373 : Elemental abund. of 3 red giants in Ter 7 (Tautvaisiene+ 2004) J/AJ/129/1607 : Equivalent widths of 4 RGB in NGC 7492 (Cohen+, 2005) Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 7 I7 --- Seq Sequential number 9 I1 --- Fib [1/2] Fiber configuration 11- 17 F7.3 deg RAdeg Right ascension in decimal degrees (J2000) 19- 26 F8.4 deg DEdeg Declination in decimal degrees (J2000) 28- 30 I3 arcsec Dist Distance from the cluster center 32- 37 F6.3 mag Vmag Johnson V magnitude 39- 43 F5.3 mag V-Ic Johnson-Cousins V-I colour index 45- 49 F5.3 mag V-K ? Johnson V-K colour index 51- 56 F6.1 km/s RV Radial velocity 58- 59 I2 --- S/N Signal-to-noise ratio 61- 64 F4.1 0.1pm e_EW ? rms uncertainty on EW 66- 70 F5.2 [Sun] [Fe/H] ? Metallicity 72- 80 A9 --- Note Notes
Byte-by-byte Description of file: table3.dat table4.dat
Bytes Format Units Label Explanations
1- 7 I7 --- Seq Sequential number 9- 12 A4 --- El Element 14- 20 F7.2 0.1nm Lambda Wavelength 22- 25 F4.2 eV Ep Excitation potential 27- 32 F6.2 --- log(gf) log Oscillator strength 34- 38 F5.1 0.1pm EW ? Equivalent width 40- 43 F4.2 --- logAbund ? log Abundance
Acknowledgements: Raffaele Gratton, gratton(at) References: Carreta et al., Paper I 2006A&A...450..523C Valenti et al., Paper II 2006, in prep.
(End) Patricia Vannier [CDS] 16-May-2006
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