Chemical composition and evolutionary status of nine UV-bright stars in five globular clusters from VLT/UVES spectra

Details Chemical composition and evolutionary status of nine UV-bright stars in five globular clusters from VLT/UVES spectra Chemical composition and evolutionary status of nine UV-bright stars in five globular clusters from VLT/UVES spectra

Aug 2004

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004a%26a...423..353j&link_type=abstract

Astronomy and Astrophysics, v.423, p.353-362 (2004)

Astronomy and Astrophysics

Astrophysics

6

Stars: Abundances, Stars : Agb And Post-Agb, Galaxy: Globular Clusters : General

Scientific paper

We have derived the chemical composition of nine UV-bright stars belonging to five Galactic globular clusters of various metallicities ([Fe/H] from -1.0 to -2.4 dex). The analyses are based on high resolution spectra obtained with the UV-Visual Echelle Spectrograph (UVES) at VLT-UT2. The evolutionary status of the stars is assessed from the chemical analysis and location in the H-R diagram. The star ID7 in NGC 5986 is confirmed as a bona fide post-asymptotic giant branch star (post-AGB) whereas the high-luminosity star ID6 has probably left the AGB before the third dredge-up. ZNG 1 in NGC 6712 shows an overabundance of sodium, oxygen, and silicon similar to overabundances we find in the UV-bright star ID6 in NGC 5986; both stars could be in a post-early-AGB (PEAGB) phase of evolution. The UV-bright star ZNG 7 in NGC 6218 seems to be an AGB star. The stars V-4 and ZNG 5 in NGC 6656 are in a post-horizontal-branch phase of evolution, with V-4 being significantly overabundant in heavy elements. The origin of these overabundances is discussed in the context of the evolutionary versus primordial scenario. The three UV-bright stars K 260, K 996 and K 1082 observed in the very metal-deficient globular cluster NGC 7078 are post-horizontal-branch stars, one of them being slightly enriched in s-elements but with a luminosity too low for third dredge-up to have occured. The abundance patterns of K 1082 in NGC 7078 seem to indicate the presence of mild diffusion and a radiative levitation process, already reported in the blue HB stars of M 13 (Behr et al. \cite{Behr1999}, ApJ, 517, L135) and NGC 6752 (Moehler et al. \cite{Moehler1999}, A&A, 339, 537).
Based on data collected at Paranal Observatory (ESO, Chile), program identifier ID 69.D-0081.
Full Table \ref{abund} is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/423/353
Appendix is only available in electronic form at http://www.edpsciences.org

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