dc.contributor.author |
Ambika, S |
|
dc.contributor.author |
Parthasarathy, M |
|
dc.contributor.author |
Aoki, W |
|
dc.contributor.author |
Fujii, T |
|
dc.contributor.author |
Nakada, Y |
|
dc.contributor.author |
Ita, Y |
|
dc.contributor.author |
Izumiura, H |
|
dc.date.accessioned |
2008-09-12T15:51:53Z |
|
dc.date.available |
2008-09-12T15:51:53Z |
|
dc.date.issued |
2004-04 |
|
dc.identifier.citation |
Astronomy and Astrophysics, Vol. 417, No. 1, pp. 293 - 300 |
en |
dc.identifier.issn |
0004-6361 |
|
dc.identifier.uri |
http://hdl.handle.net/2248/3600 |
|
dc.description.abstract |
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 ( R ≈ 45 000 ) spectrum of the object, we derive the atmospheric parameters to be Teff = 8500± 250 K, log g = 2.5 ± 0.5 and [Fe/H]= -1.5. 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.
Based on observations obtained with the Subaru 8.2 m Telescope, which is operated by the National Astronomical Observatory of Japan.
Table \ref{t3} is only available in electronic form at http://www.edpsciences.org |
en |
dc.language.iso |
en |
en |
dc.publisher |
EDP Sciences |
en |
dc.relation.uri |
http://www.aanda.org/index.php?option=article&access=doi&doi=10.1051/0004-6361:20031759 |
en |
dc.subject |
Stars: abundances |
en |
dc.subject |
Stars: evolution |
en |
dc.subject |
Stars: Population II |
en |
dc.subject |
Stars: horizontal-branch |
en |
dc.subject |
Galaxy: globular cluster: individual: M 13 |
en |
dc.subject |
Stars: individual: ZNG 4 |
en |
dc.title |
Chemical composition of UV-bright star ZNG 4 in the globular cluster M 13 |
en |
dc.type |
Article |
en |