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 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:
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FileName Lrecl Records Explanations
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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
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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
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Bytes Format Units Label Explanations
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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
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Byte-by-byte Description of file: table3.dat table4.dat
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Bytes Format Units Label Explanations
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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
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Acknowledgements: Raffaele Gratton, gratton(at)pd.astro.it
References:
Carreta et al., Paper I 2006A&A...450..523C 2006A&A...450..523C
Valenti et al., Paper II 2006, in prep.
(End) Patricia Vannier [CDS] 16-May-2006