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J/A+A/287/927     Abundances for lines of n-capture in 19 stars  (Gratton+ 1994)
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Abundances of neutron-capture elements in metal-poor stars
     Gratton R.G., Sneden C.
    <Astron. Astrophys. 287, 927 (1994)>
    =1994A&A...287..927G
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ADC_Keywords: Stars, dwarfs; Spectroscopy; Abundances
Keywords: stars: abundances - stars: population II - sun: abundances -
          nucleosynthesis - Galaxy: evolution

Abstract:
    We use a large set of high S/N, high resolution spectra of 19 stars with 
    -2.8<[Fe/H]<0 to study the abundances of neutron-rich elements in 
    metal-poor stars. Basic data (atmospheric parameters, iron abundances, 
    abundance indices, atomic and line parameters) are carefully examined both
    for the Sun and for the program stars, and extensive use is made of 
    comparisons with synthetic spectra. New analyses of solar abundances of  
    Sr, La, and Ce are presented; deduced abundances agree well with meteoritic
    results. Our stellar abundances are briefly compared with nucleosynthesis 
    predictions. The main results are: 1. Those elements whose solar abundances
    are mainly attributed to the s-process (e.g. Ba and La) are overdeficient 
    in extremely metal-poor stars ([Fe/H]<-2) with respect to those elements 
    whose solar abundances are mainly attributed to the r-process (e.g. Eu). 
    We did not find any clear evidence for a plateau in abundance ratios like 
    [Ba/Eu] at these low values of [Fe/H]. 2. Eu itself begins to decline 
    (with respect either to Fe or Mg) in the most metal-poor stars, with 
    perhaps a sharp drop in stars with [Fe/H]<-2.5. If the r-process mainly 
    occurs in SN explosions of massive stars, then the abundances of its 
    products in the ejecta are a function of initial stellar mass and/or 
    metallicity. 3. The abundance pattern of neutron-capture elements in 
    metal-poor stars show clear differences with respect to scaled 
    solar-system r-process nucleosynthesis predictions; e.g. there is a 
    relative excess of Ba (attributed mainly to the s-process). This pattern 
    may be explained if the contribution of the s-process to the solar 
    abundances of heavy elements is overestimated, or the production of heavy 
    elements through the r-process was different when [Fe/H] was much lower 
    than the present value, or there was an early onset of the contribution by
    the main component of the s-process in the Galactic chemical evolution. 

File Summary:
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 FileName    Lrecl    Records    Explanations
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ReadMe          80          .    This file
table3          60       1311    Equivalent widths and abundances for lines of
                                  n-capture elements in 19 metal-poor stars
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Byte-by-byte Description of file: table3
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   Bytes Format  Units   Label    Explanations
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   1-  9  A9     ---     HD       HD name
  11- 16  A6     ---     E        Element
  22- 28  F7.2   0.1nm   W        Wavelength
  32- 35  F4.2   eV      EP       Potential energy
  38- 42  F5.2   ---     log(gf)  Oscillator strength
      44  A1     ---     l_EW     Limit flag on equivalent width
  45- 49  F5.1   0.1pm   EW       []? Equivalent width
      50  A1     ---     n        [ s] When s, the line was saturated
      51  A1     ---     l_log(A) Limit flag on abundance
  52- 56  F5.2   ---     log(A)   []? Abundance
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(End)                                          Patricia Bauer [CDS] 31-Jan-1994