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First Stars. II. Elemental abundances in the extremely metal-poor star CS 22949--037. A diagnostic of early massive supernovae

Depagne, E.; Hill, V.; Spite, M.; Spite, F.; Plez, B.; Beers, T. C.; Barbuy, B.; Cayrel, R.; Andersen, J. and Bonifacio, P., et al. (2002) In Astronomy & Astrophysics 390(1). p.187-198
Abstract
CS 22949-037 is one of the most metal-poor giants known ([Fe/H]~-4.0),and it exhibits large overabundances of carbon and nitrogen (Norris etal.). Using VLT-UVES spectra of unprecedented quality, regardingresolution and S/N ratio, covering a wide wavelength range (from lambda= 350 to 900 nm), we have determined abundances for 21 elements in thisstar over a wide range of atomic mass. The major new discovery is anexceptionally large oxygen enhancement, [O/Fe] = 1.97+/-0.1, as measuredfrom the [O I] line at 630.0 nm. We find an enhancement of [N/Fe] of2.56+/- 0.2, and a milder one of [C/Fe] = 1.17+/-0.1, similar to thosealready reported in the literature. This implies Z<SUB>star </SUB>=0.01Z<SUB>sun</SUB>. We also find... (More)
CS 22949-037 is one of the most metal-poor giants known ([Fe/H]~-4.0),and it exhibits large overabundances of carbon and nitrogen (Norris etal.). Using VLT-UVES spectra of unprecedented quality, regardingresolution and S/N ratio, covering a wide wavelength range (from lambda= 350 to 900 nm), we have determined abundances for 21 elements in thisstar over a wide range of atomic mass. The major new discovery is anexceptionally large oxygen enhancement, [O/Fe] = 1.97+/-0.1, as measuredfrom the [O I] line at 630.0 nm. We find an enhancement of [N/Fe] of2.56+/- 0.2, and a milder one of [C/Fe] = 1.17+/-0.1, similar to thosealready reported in the literature. This implies Z<SUB>star </SUB>=0.01Z<SUB>sun</SUB>. We also find carbon isotopic ratios<SUP>12</SUP>C/<SUP>13</SUP>C =4+/-2.0 and <SUP>13</SUP>C/<SUP>14</SUP>N=0.03 <SUP>+0.035</SUP><SUB>-0.015</SUB>, close to the equilibrium valueof the CN cycle. Lithium is not detected. Na is strongly enhanced([Na/Fe] = +2.1 +/- 0.2), while S and K are not detected. Thesilicon-burning elements Cr and Mn are underabundant, while Co and Znare overabundant ([Zn/Fe]=+0.7). Zn is measured for the first time insuch an extremely metal-poor star. The abundances of the neutron-captureelements Sr, Y, and Ba are strongly decreasing with the atomic number ofthe element: [Sr/Fe] ~ +0.3, [Y/Fe] ~ -0.1, and [Ba/Fe] ~ -0.6. Amongpossible progenitors of CS 22949-037, we discuss the pair-instabilitysupernovae. Such very massive objects indeed produce large amounts ofoxygen, and have been found to be possible sources of primary nitrogen.However, the predicted odd/even effect is too large, and the predictedZn abundance much too low. Other scenarios are also discussed. Inparticular, the yields of a recent model (Z35Z) from Heger and Woosleyare shown to be in fair agreement with the observations. The onlydiscrepant prediction is the very low abundance of nitrogen, possiblycurable by taking into account other effects such as rotationallyinduced mixing. Alternatively, the absence of lithium in our star, andthe values of the isotopic ratios <SUP>12</SUP>C/<SUP>13</SUP>C and<SUP>13</SUP>C/<SUP>14</SUP>N close to the equilibrium value of the CNcycle, suggest that the CNO abundances now observed might have beenaltered by nuclear processing in the star itself. A 30-40M<SUB>sun</SUB> supernova, with fallback, seems the most likelyprogenitor for CS 22949-037. Based on observations made with the ESOVery Large Telescope at Paranal Observatory, Chile (programme ID165.N-0276(A)). (Less)
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stars: individual: object {BPS CS 22949-037, stars: fundamental parameters, stars: abundances
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Astronomy & Astrophysics
volume
390
issue
1
pages
187 - 198
publisher
EDP Sciences
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  • wos:000176980000023
  • scopus:0036647699
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0004-6361
DOI
10.1051/0004-6361:20020687
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English
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2007-07-12 15:48:23
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@article{a4fc78da-9ea4-4824-8e24-51d2b9eebaf3,
  abstract     = {CS 22949-037 is one of the most metal-poor giants known ([Fe/H]~-4.0),and it exhibits large overabundances of carbon and nitrogen (Norris etal.). Using VLT-UVES spectra of unprecedented quality, regardingresolution and S/N ratio, covering a wide wavelength range (from lambda= 350 to 900 nm), we have determined abundances for 21 elements in thisstar over a wide range of atomic mass. The major new discovery is anexceptionally large oxygen enhancement, [O/Fe] = 1.97+/-0.1, as measuredfrom the [O I] line at 630.0 nm. We find an enhancement of [N/Fe] of2.56+/- 0.2, and a milder one of [C/Fe] = 1.17+/-0.1, similar to thosealready reported in the literature. This implies Z&lt;SUB&gt;star &lt;/SUB&gt;=0.01Z&lt;SUB&gt;sun&lt;/SUB&gt;. We also find carbon isotopic ratios&lt;SUP&gt;12&lt;/SUP&gt;C/&lt;SUP&gt;13&lt;/SUP&gt;C =4+/-2.0 and &lt;SUP&gt;13&lt;/SUP&gt;C/&lt;SUP&gt;14&lt;/SUP&gt;N=0.03 &lt;SUP&gt;+0.035&lt;/SUP&gt;&lt;SUB&gt;-0.015&lt;/SUB&gt;, close to the equilibrium valueof the CN cycle. Lithium is not detected. Na is strongly enhanced([Na/Fe] = +2.1 +/- 0.2), while S and K are not detected. Thesilicon-burning elements Cr and Mn are underabundant, while Co and Znare overabundant ([Zn/Fe]=+0.7). Zn is measured for the first time insuch an extremely metal-poor star. The abundances of the neutron-captureelements Sr, Y, and Ba are strongly decreasing with the atomic number ofthe element: [Sr/Fe] ~ +0.3, [Y/Fe] ~ -0.1, and [Ba/Fe] ~ -0.6. Amongpossible progenitors of CS 22949-037, we discuss the pair-instabilitysupernovae. Such very massive objects indeed produce large amounts ofoxygen, and have been found to be possible sources of primary nitrogen.However, the predicted odd/even effect is too large, and the predictedZn abundance much too low. Other scenarios are also discussed. Inparticular, the yields of a recent model (Z35Z) from Heger and Woosleyare shown to be in fair agreement with the observations. The onlydiscrepant prediction is the very low abundance of nitrogen, possiblycurable by taking into account other effects such as rotationallyinduced mixing. Alternatively, the absence of lithium in our star, andthe values of the isotopic ratios &lt;SUP&gt;12&lt;/SUP&gt;C/&lt;SUP&gt;13&lt;/SUP&gt;C and&lt;SUP&gt;13&lt;/SUP&gt;C/&lt;SUP&gt;14&lt;/SUP&gt;N close to the equilibrium value of the CNcycle, suggest that the CNO abundances now observed might have beenaltered by nuclear processing in the star itself. A 30-40M&lt;SUB&gt;sun&lt;/SUB&gt; supernova, with fallback, seems the most likelyprogenitor for CS 22949-037. Based on observations made with the ESOVery Large Telescope at Paranal Observatory, Chile (programme ID165.N-0276(A)).},
  author       = {Depagne, E. and Hill, V. and Spite, M. and Spite, F. and Plez, B. and Beers, T. C. and Barbuy, B. and Cayrel, R. and Andersen, J. and Bonifacio, P. and François, P. and Nordström, Birgitta and Primas, F.},
  issn         = {0004-6361},
  keyword      = {stars: individual: object {BPS CS 22949-037,stars: fundamental parameters,stars: abundances},
  language     = {eng},
  number       = {1},
  pages        = {187--198},
  publisher    = {EDP Sciences},
  series       = {Astronomy & Astrophysics},
  title        = {First Stars. II. Elemental abundances in the extremely metal-poor star CS 22949--037. A diagnostic of early massive supernovae},
  url          = {http://dx.doi.org/10.1051/0004-6361:20020687},
  volume       = {390},
  year         = {2002},
}