2004A&A...423..353J -
Astronomy and Astrophysics, volume 423353-362 (2004/8-3)
Chemical composition and evolutionary status of nine UV-bright stars in five globular clusters from VLT/UVES spectra.
JASNIEWICZ G., DE LAVERNY P., PARTHASARATHY M., LEBRE A. and THEVENIN F.
Abstract (from CDS):
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 -2.4dex). 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.,
1999ApJ...517L.135B) and NGC 6752 (Moehler et al.,
1999A&A...346L...1M).
Abstract Copyright:
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Journal keyword(s):
stars: abundances - stars : AGB and post-AGB - Galaxy: globular clusters: general
VizieR on-line data:
<Available at CDS (J/A+A/423/353): table6.dat table6.tex>
CDS comments:
Table 2 : NGC 6656 V-4 is NGC 6656 5004 in Simbad.
Simbad objects:
25
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