J/A+A/403/1105 Extremely metal-poor giants equivalent widths (Francois+, 2003)
First stars. III.
A detailed elemental abundance study of four extremely metal-poor giant stars
Francois P., Depagne E., Hill V., Spite M., Spite F., Plez B.,
Beers T.C., Barbuy B., Cayrel R., Andersen J., Bonifacio P., Molaro P.,
Nordstroem F., Primas B.
<Astron. Astrophys. 403, 1105 (2003)>
=2003A&A...403.1105F 2003A&A...403.1105F
ADC_Keywords: Stars, giant ; Stars, halo ; Stars, metal-deficient ;
Equivalent widths
Keywords: stars: abundances - stars: population II - Galaxy: abundances -
Galaxy: halo - nuclear reactions, nucleosynthesis, abundances
Abstract:
This paper reports detailed abundance analyses for four extremely
metal-poor (XMP) giant stars with [Fe/H]←3.8, based on
high-resolution, high- S/N spectra from the ESO VLT (Kueyen/UVES) and
LTE model atmosphere calculations. The derived [α/Fe] ratios in
our sample exhibit a small dispersion, confirming previous findings in
the literature, i.e. a constant overabundance of the α-elements
with a very small (if any) dependence on [Fe/H]. In particular, the
very small scatter we determine for [Si/Fe] suggests that this element
shows a constant overabundance at very low metallicity, a conclusion
which could not have been derived from the widely scattered [Si/Fe]
values reported in the literature for less metal-poor stars. For the
iron-peak elements, our precise abundances for the four XMP stars in
our sample confirm the decreasing trend of Cr and Mn with decreasing
[Fe/H], as well as the increasing trend for Co and the absence of any
trend for Sc and Ni. In contrast to the significant spread of the
ratios [Sr/Fe] and [Ba/Fe], we find [Sr/Ba] in our sample to be
roughly solar, with a much lower dispersion than previously found for
stars in the range -3.5<[Fe/H]←2.5.
Description:
The observations were carried out during several observing runs in
2000 and 2001 using the VLT-Kueyen telescope and UVES spectrograph.
The log of the observations and spectrograph settings can be found in
Table 1.
Objects: (Adopted atmospheric parameters)
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RA (2000) DE Designation(s) Bmag Vmag Teff logg Vtur
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00 46 36.2 -37 39 34 CD -38 245 12.00 4900 1.7 2.0
20 20 51.2 -39 53 30 BPS CS 22885-096 14.02 13.33 5100 1.9 1.4
13 42 00.6 +17 48 33 BPS BS 16467-062 14.02 4800 1.3 2.2
03 14 20.6 -10 35 10 BPS CS 22172-002 13.54 12.73 4900 2.0 2.0
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table5.dat 97 258 Equivalent widths for program stars
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Table 1: Observing log for the programme stars. Exposure times combine several
exposures obtained in different observing runs, and S/N ratios are
given for the co-added spectra.
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Total exposure time S/N ratio
Star Vmag Date Blue yellow Red
396nm 573nm 850nm 400nm 510nm 630nm
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CD -38 245 12.01 Jul. 2000 7200 3600 3600 150 150 200
Aug. 2000
BS 16467 062 14.09 Jun. 2001 10200 7200 3600 90 140 170
Jul. 2001
CS 22172 002 12.73 Oct. 2000 7494 3600 3900 130 200 330
CS 22885 096 13.33 Jul. 2000 15835 9184 6600 160 250 410
Aug. 2000
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See also:
J/ApJS/123/639 : UBV photometry of metal-weak candidates (Norris+, 1999)
Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- Element Chemical element and ionization stage
11- 18 F8.3 0.1nm Lambda Wavelength in Angstroem
24- 27 F4.2 eV EP Line Excitation potential of the line energy
33- 38 F6.3 --- loggf Oscillator strength (1)
44- 50 F7.3 0.1pm EW1 ? Equivalent width of the line for CD-38 245
56- 62 F7.3 0.1pm EW2 ? Equivalent width of the line for CS 22885-096
69- 75 F7.3 0.1pm EW3 ? Equivalent width of the line for BS 16467-062
84- 90 F7.3 0.1pm EW4 ? Equivalent width of the line for CS 22172-002
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Note (1): The log(gf) are the same as in Hill et al. (2002A&A...387..560H 2002A&A...387..560H).
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Acknowledgements: Patrick Francois
References:
Hill et al., Paper I 2002A&A...387..560H 2002A&A...387..560H
Depagne et al., Paper II 2002A&A...390..187D 2002A&A...390..187D
(End) Patricia Bauer [CDS] 27-May-2003