Volume 417, Number 1, April I 2004
|Page(s)||293 - 300|
|Published online||16 March 2004|
Indian Institute of Astrophysics, Koramangala, Bangalore, 560034, India
2 National Astronomical Observatory, Mitaka, Tokyo 181-8588, Japan
3 Faculty of Science, Kagoshima University, 1-21-35 Korimoto, Kagoshima 890-0065, Japan
4 Institute of Astronomy, The University of Tokyo, Mitaka, Tokyo, 181-0015, Japan
5 Kiso Observatory, Institute of Astronomy, University of Tokyo, Mitake, Kiso, Nagano 397-0101, Japan
6 Okayama Astrophysical Observatory, National Astronomical Observatory, Kamogata, Okayama 719-0232, Japan
Corresponding author: S. Ambika, firstname.lastname@example.org
Accepted: 18 November 2003
We present a detailed model-atmosphere analysis of ZNG 4, a UV-bright star in the globular cluster M 13. From the analysis of a high resolution () spectrum of the object, we derive the atmospheric parameters to be K, log and . Except for magnesium, chromium and strontium, all other even Z elements are enhanced with titanium and calcium being overabundant by a factor of 0.8 dex. Sodium is enhanced by a factor of 0.2 dex. The luminosity of ZNG 4 and its position in the color-magnitude diagram of the cluster indicate that it is a Supra Horizontal Branch (SHB) (post-HB) star. The underabundance of He and overabundances of Ca, Ti, Sc and Ba in the photosphere of ZNG 4 indicate that diffusion and radiative levitation of elements may be in operation in M 13 post-HB stars even at Teff of 8500 K. Detailed and more accurate abundance analysis of post-HB stars in several globular clusters is needed to further understand their abundance anomalies.
Key words: stars: abundances / stars: evolution / stars: Population II / stars: horizontal-branch / Galaxy: globular cluster: individual: M 13 / stars: individual: ZNG 4
© ESO, 2004
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.