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Abundances in bulge stars from high-resolution, near-IR spectra I. The CNO elements observed during the science verification of CRIRES at VLT

Ryde, Nils LU ; Edvardsson, B.; Gustafsson, B.; Eriksson, K.; Kauefl, H. U.; Siebenmorgen, R. and Smette, A. (2009) In Astronomy & Astrophysics 496(3). p.141-701
Abstract
Context. The formation and evolution of the Milky Way bulge is not yet well understood and its classification is ambiguous. Constraints can, however, be obtained by studying the abundances of key elements in bulge stars. Aims. The aim of this study is to determine the chemical evolution of C, N, O, and a few other elements in stars in the Galactic bulge, and to discuss the sensitivities of the derived abundances from molecular lines. Methods. High-resolution, near-infrared spectra in the H band were recorded using the CRIRES spectrometer on the Very Large Telescope. Due to the high and variable visual extinction in the line-of-sight towards the bulge, an analysis in the near-IR is preferred. The C, N, and O abundances can all be determined... (More)
Context. The formation and evolution of the Milky Way bulge is not yet well understood and its classification is ambiguous. Constraints can, however, be obtained by studying the abundances of key elements in bulge stars. Aims. The aim of this study is to determine the chemical evolution of C, N, O, and a few other elements in stars in the Galactic bulge, and to discuss the sensitivities of the derived abundances from molecular lines. Methods. High-resolution, near-infrared spectra in the H band were recorded using the CRIRES spectrometer on the Very Large Telescope. Due to the high and variable visual extinction in the line-of-sight towards the bulge, an analysis in the near-IR is preferred. The C, N, and O abundances can all be determined simultaneously from the numerous molecular lines in the wavelength range observed. Results. The three giant stars in Baade's window presented here are the first bulge stars observed with CRIRES during its science verification observations. We have especially determined the C, N, and O abundances, with uncertainties of less than 0.20 dex, from CO, CN, and OH lines. Since the systematic uncertainties in the derived C, N, and O abundances due to uncertainties in the stellar fundamental parameters, notably T-eff, are significant, a detailed discussion of the sensitivities of the derived abundances is included. We find good agreement between near-IR and optically determined O, Ti, Fe, and Si abundances. Two of our stars show a solar [C+N/Fe], suggesting that these giants have experienced the first dredge-up and that the oxygen abundance should reflect the original abundance of the giants. The two giants fit into the picture, in which there is no significant difference between the oxygen abundance in bulge and thick-disk stars. Our determination of the sulphur abundances is the first for bulge stars. The high [ S/Fe] values for all the stars indicate a high star-formation rate in an early phase of the bulge evolution. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
stars: abundances, Galaxy: bulge, infrared: stars
in
Astronomy & Astrophysics
volume
496
issue
3
pages
141 - 701
publisher
EDP Sciences
external identifiers
  • wos:000264665600013
  • scopus:65949119518
ISSN
0004-6361
DOI
10.1051/0004-6361/200811070
language
English
LU publication?
yes
id
dbeec3e6-2557-45e1-b2a0-c57575fcc2c0 (old id 1401641)
date added to LUP
2009-06-15 10:57:07
date last changed
2017-07-30 04:23:59
@article{dbeec3e6-2557-45e1-b2a0-c57575fcc2c0,
  abstract     = {Context. The formation and evolution of the Milky Way bulge is not yet well understood and its classification is ambiguous. Constraints can, however, be obtained by studying the abundances of key elements in bulge stars. Aims. The aim of this study is to determine the chemical evolution of C, N, O, and a few other elements in stars in the Galactic bulge, and to discuss the sensitivities of the derived abundances from molecular lines. Methods. High-resolution, near-infrared spectra in the H band were recorded using the CRIRES spectrometer on the Very Large Telescope. Due to the high and variable visual extinction in the line-of-sight towards the bulge, an analysis in the near-IR is preferred. The C, N, and O abundances can all be determined simultaneously from the numerous molecular lines in the wavelength range observed. Results. The three giant stars in Baade's window presented here are the first bulge stars observed with CRIRES during its science verification observations. We have especially determined the C, N, and O abundances, with uncertainties of less than 0.20 dex, from CO, CN, and OH lines. Since the systematic uncertainties in the derived C, N, and O abundances due to uncertainties in the stellar fundamental parameters, notably T-eff, are significant, a detailed discussion of the sensitivities of the derived abundances is included. We find good agreement between near-IR and optically determined O, Ti, Fe, and Si abundances. Two of our stars show a solar [C+N/Fe], suggesting that these giants have experienced the first dredge-up and that the oxygen abundance should reflect the original abundance of the giants. The two giants fit into the picture, in which there is no significant difference between the oxygen abundance in bulge and thick-disk stars. Our determination of the sulphur abundances is the first for bulge stars. The high [ S/Fe] values for all the stars indicate a high star-formation rate in an early phase of the bulge evolution.},
  author       = {Ryde, Nils and Edvardsson, B. and Gustafsson, B. and Eriksson, K. and Kauefl, H. U. and Siebenmorgen, R. and Smette, A.},
  issn         = {0004-6361},
  keyword      = {stars: abundances,Galaxy: bulge,infrared: stars},
  language     = {eng},
  number       = {3},
  pages        = {141--701},
  publisher    = {EDP Sciences},
  series       = {Astronomy & Astrophysics},
  title        = {Abundances in bulge stars from high-resolution, near-IR spectra I. The CNO elements observed during the science verification of CRIRES at VLT},
  url          = {http://dx.doi.org/10.1051/0004-6361/200811070},
  volume       = {496},
  year         = {2009},
}