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Abundances of RGB stars in NGC 6752

Grundahl, F; Briley, M; Nissen, P E and Feltzing, Sofia LU (2002) In Astronomy & Astrophysics 385. p.14-17
Abstract
Abundances of O, Fe, Al, Mg, Na and Li determined from high-resolutionand high signal-to-noise spectra of 21 red giant branch (RGB) stars inthe globular cluster NGC 6752 are presented. We demonstrate that theStrömgren c<SUB>1</SUB> index correlates extremely well with themeasured NH, CH and CN indices and that variations in c<SUB>1</SUB> aredue to differences in UV NH band strengths. As shown by Grundahl et al.(cite{grundahl02}), the RGB stars in all 20 globular clusters surveyedpossess large star-to-star variations in their c<SUB>1</SUB> index,which we interpret as significant inhomogeneities in N abundances. Thewell known relations among O and Na and Mg and Al as well as with CN,CH, and NH are also... (More)
Abundances of O, Fe, Al, Mg, Na and Li determined from high-resolutionand high signal-to-noise spectra of 21 red giant branch (RGB) stars inthe globular cluster NGC 6752 are presented. We demonstrate that theStrömgren c<SUB>1</SUB> index correlates extremely well with themeasured NH, CH and CN indices and that variations in c<SUB>1</SUB> aredue to differences in UV NH band strengths. As shown by Grundahl et al.(cite{grundahl02}), the RGB stars in all 20 globular clusters surveyedpossess large star-to-star variations in their c<SUB>1</SUB> index,which we interpret as significant inhomogeneities in N abundances. Thewell known relations among O and Na and Mg and Al as well as with CN,CH, and NH are also present in these stars, some of which are fainterthan the RGB bump. We find that the Li (6708 Å) equivalent widthbecomes too small to be measured as the luminosity of the stars increaseabove the luminosity of the RGB bump. Taken together, these data enforcethe results of Gratton et al. (cite{gratton01}) for turnoff andsub-giant branch stars, and suggest that in this cluster the abundancecorrelations observed among the brighter giants are in place prior toappreciable RGB ascent and likely due to previous generation(s) ofstars, rather than due to mixing in the observed stars. Based onobservations obtained with the ESO Very Large Telescope UVESspectrograph for programme 65.L-0165(A). Based on observations obtainedwith the Danish 1.5 m telescope at the European Southern Observatory, LaSilla, Chile. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
GLOBULAR CLUSTERS, INDIVIDUAL: NGC 6752, STARS: ABUNDANCES, MIXING
in
Astronomy & Astrophysics
volume
385
pages
14 - 17
publisher
EDP Sciences
external identifiers
  • wos:000174804600003
  • scopus:0036531143
ISSN
0004-6361
DOI
10.1051/0004-6361:20020264
language
English
LU publication?
yes
id
7202023c-1814-4dd7-96ad-3a0803cf3706 (old id 130373)
date added to LUP
2007-07-13 10:11:24
date last changed
2017-12-10 04:31:15
@article{7202023c-1814-4dd7-96ad-3a0803cf3706,
  abstract     = {Abundances of O, Fe, Al, Mg, Na and Li determined from high-resolutionand high signal-to-noise spectra of 21 red giant branch (RGB) stars inthe globular cluster NGC 6752 are presented. We demonstrate that theStrömgren c&lt;SUB&gt;1&lt;/SUB&gt; index correlates extremely well with themeasured NH, CH and CN indices and that variations in c&lt;SUB&gt;1&lt;/SUB&gt; aredue to differences in UV NH band strengths. As shown by Grundahl et al.(cite{grundahl02}), the RGB stars in all 20 globular clusters surveyedpossess large star-to-star variations in their c&lt;SUB&gt;1&lt;/SUB&gt; index,which we interpret as significant inhomogeneities in N abundances. Thewell known relations among O and Na and Mg and Al as well as with CN,CH, and NH are also present in these stars, some of which are fainterthan the RGB bump. We find that the Li (6708 Å) equivalent widthbecomes too small to be measured as the luminosity of the stars increaseabove the luminosity of the RGB bump. Taken together, these data enforcethe results of Gratton et al. (cite{gratton01}) for turnoff andsub-giant branch stars, and suggest that in this cluster the abundancecorrelations observed among the brighter giants are in place prior toappreciable RGB ascent and likely due to previous generation(s) ofstars, rather than due to mixing in the observed stars. Based onobservations obtained with the ESO Very Large Telescope UVESspectrograph for programme 65.L-0165(A). Based on observations obtainedwith the Danish 1.5 m telescope at the European Southern Observatory, LaSilla, Chile.},
  author       = {Grundahl, F and Briley, M and Nissen, P E and Feltzing, Sofia},
  issn         = {0004-6361},
  keyword      = {GLOBULAR CLUSTERS,INDIVIDUAL: NGC 6752,STARS: ABUNDANCES,MIXING},
  language     = {eng},
  pages        = {14--17},
  publisher    = {EDP Sciences},
  series       = {Astronomy & Astrophysics},
  title        = {Abundances of RGB stars in NGC 6752},
  url          = {http://dx.doi.org/10.1051/0004-6361:20020264},
  volume       = {385},
  year         = {2002},
}