Issue |
A&A
Volume 455, Number 1, August III 2006
|
|
---|---|---|
Page(s) | 271 - 281 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361:20064957 | |
Published online | 31 July 2006 |
Na-O anticorrelation and HB
III. The abundances of NGC 6441 from FLAMES-UVES spectra
1
INAF – Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, 35122 Padova, Italy e-mail: raffaele.gratton@oapd.inaf.it
2
INAF – Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
3
Dipartimento di Astronoma, Università di Padova, Vicolo dell'Osservatorio 5, 35122 Padova, Italy
4
Dipartimento di Astronoma, Università di Bologna, via Ranzani 1, 40127 Bologna, Italy
Received:
2
February
2006
Accepted:
10
April
2006
Aims.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.
Methods.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] = dex, 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 α-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.
Key words: stars: abundances / stars: atmospheres / stars: population II / Galaxy: globular clusters: general / galaxies: clusters: individual: NGC 6441
© ESO, 2006
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.