J/A+A/350/955 Atmospheric parameters in metal-poor stars. II (Gratton+, 1999)
Abundances of light elements in metal-poor stars.
II. Non-LTE abundance corrections
Gratton R.G., Carretta E., Eriksson K., Gustafsson B.
<Astron. Astrophys. 350, 955 (1999)>
=1999A&A...350..955G 1999A&A...350..955G
ADC_Keywords: Stars, metal-deficient ; Abundances ; Models, atmosphere
Keywords: stars: abundances - stars: atmospheres - stars: population II -
Sun: abundances
Abstract:
We present non-LTE corrections to abundances of Fe, O, Na, and Mg
derived from LTE analyses of F-K stars over a broad range of
gravities and metal abundances; they were obtained using statistical
equilibrium calculations and new model atoms. Line opacity was
considered by means of an empirical procedure where it was
attributed to a veil of weak Fe I lines; in the case of solar-type
dwarfs, results were compared with those obtained using (LTE) mean
intensities computed from OSMARCS models. We think that the empirical
procedure produces better results for metal-poor stars, while mean
intensities should perhaps be preferred for the Sun (where departures
from LTE are anyway not very large). Collisions with both electrons
and H I atoms were considered. Since cross sections for this second
mechanism are very poorly known, we calibrated them empirically by
matching observations of RR Lyrae variables at minimum light
(discussed in Clementini et al., 1995, Cat. J/AJ/110/2319). These
stars were selected because non-LTE effects are expected to be larger
in these stars than in those usually considered in the study of the
chemical evolution of the Galaxy (cool main sequence and red giant
branch stars). We found that different non-LTE mechanisms are
important for the different species and transitions considered; on the
whole, our calculations yielded moderate corrections to LTE abundances
for high excitation O lines in warm dwarfs and giants, Na and Mg lines
in giants and supergiants, and Fe I lines in F-supergiants (where
corrections becomes very large for IR O lines). Non-LTE corrections
were found to be negligible in the other cases studied.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
levels.dat 42 138 Levels for Fe I, O I, Na I and Mg I atoms
bound.dat 43 160 Bound-bound transitions
abundcor.dat 111 520 Corrections to LTE abundances
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See also:
J/A+A/314/191 : Atmospheric parameters in metal-poor stars. I (Gratton+, 1996)
J/AJ/110/2319 : Abundances in RR Lyrae variables (Clementini+ 1995)
Byte-by-byte Description of file: levels.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- Ion Ion designation
6- 7 I2 --- Level Level
10- 17 F8.1 cm-1 E Energy
21- 22 I2 --- Weight Statistical weight
25- 31 A7 --- Ident Identification
35- 42 E8.2 cm+2 CrossSec ? Threshold Cross Section
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Byte-by-byte Description of file: bound.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- Ion Ion designation
6- 7 I2 --- UpperL Upper level
10- 11 I2 --- LowerL Lower level
13- 20 F8.1 nm Lambda Wavelength
25- 32 E8.2 --- Abs Absorption oscillator strength
36- 43 E8.2 s-1 Einst Einstein factor
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Byte-by-byte Description of file: abundcor.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- Ion Ion designation
6- 9 F4.1 [Sun] [A/H] Abundance [A/H] (logarithmic scale)
11- 18 F8.3 0.1nm Lambda Wavelength
20- 23 F4.2 eV EP Excitation Potential
25- 30 F6.1 0.1pm EW Equivalent Width
32- 36 F5.2 --- C4kK1.5 ?=-11 Correction for Teff=4000, logg=1.50 (1)
38- 43 F6.2 --- C4kK3 ?=-11 Correction for Teff=4000, logg=3.00 (1)
45- 50 F6.2 --- C4kK4.5 ?=-11 Correction for Teff=4000, logg=4.50 (1)
52- 57 F6.2 --- C5kK1.5 ?=-11 Correction for Teff=5000, logg=1.50 (1)
59- 63 F5.2 --- C5kK3 ?=-11 Correction for Teff=5000, logg=3.00 (1)
65- 70 F6.2 --- C5kK4.5 ?=-11 Correction for Teff=5000, logg=4.50 (1)
72- 77 F6.2 --- C6kK1.5 ?=-11 Correction for Teff=6000, logg=1.50 (1)
79- 84 F6.2 --- C6kK3 ?=-11 Correction for Teff=6000, logg=3.00 (1)
86- 90 F5.2 --- C6kK4.5 ?=-11 Correction for Teff=6000, logg=4.50 (1)
92- 97 F6.2 --- C7kK1.5 ?=-11 Correction for Teff=7000, logg=1.50 (1)
99-104 F6.2 --- C7kK3 ?=-11 Correction for Teff=7000, logg=3.00 (1)
106-111 F6.2 --- C7kK4.5 ?=-11 Correction for Teff=7000, logg=4.50 (1)
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Note (1): correction in the sense [A/H](NLTE) - [A/H](LTE).
The value -11 indicates that either the NLTE could not be computed,
or gave non-physical results
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Acknowledgements:
Raffaele Gratton
History:
* 19-Oct-1999: Original version
* 07-Jan-2000: File abundcor.dat was corrected with new tables
supplied by the authors.
* 25-Mar-2008: Note added about the value -11 in abundcor.dat
(End) Patricia Bauer [CDS] 07-Jan-2000