J/A+A/501/519 Extremely metal-poor turnoff stars abundances (Bonifacio+, 2009)
First stars. XII.
Abundances in extremely metal-poor turnoff stars and comparison with the giants.
Bonifacio P., Spite M., Cayrel R., Hill V., Spite F., Francois P., Plez B.,
Ludwig H.-G., Caffau E., Molaro P., Depagne E., Andersen J., Barbuy B.,
Beers T.C., Nordstroem B., Primas F.
<Astron. Astrophys. 501, 519 (2009)>
=2009A&A...501..519B 2009A&A...501..519B (SIMBAD/NED BibCode)
ADC_Keywords: Stars, halo ; Stars, metal-deficient ; Stars, giant ; Abundances ;
Radial velocities ; Equivalent widths ; Stars, population II
Keywords: Galaxy: abundances - Galaxy: halo - Galaxy: evolution -
stars: abundances - stars: population II - stars: supernovae: general
Abstract:
The detailed chemical abundances of extremely metal-poor (EMP) stars
are key guides to understanding the early chemical evolution of the
Galaxy. Most existing data, however, treat giant stars that may have
experienced internal mixing later.
We aim to compare the results for giants with new, accurate abundances
for all observable elements in 18 EMP turnoff stars. VLT/UVES spectra
at ∼45000 and S/N ∼130 per pixel (330-1000nm) are analysed with
OSMARCS model atmospheres and the TURBOSPECTRUM code to derive
abundances for C, Mg, Si, Ca, Sc, Ti, Cr, Mn, Co, Ni, Zn, Sr, and Ba.
For Ca, Ni, Sr, and Ba, we find excellent consistency with our earlier
sample of EMP giants, at all metallicities. However, our abundances of
C, Sc, Ti, Cr, Mn and Co are ∼0.2dex larger than in giants of similar
metallicity. Mg and Si abundances are ∼0.2dex lower (the giant
[Mg/Fe] values are slightly revised), while Zn is again ∼0.4dex
higher than in giants of similar [Fe/H] (6 stars only). For C, the
dwarf/giant discrepancy could possibly have an astrophysical cause,
but for the other elements it must arise from shortcomings in the
analysis. Approximate computations of granulation (3D) effects yield
smaller corrections for giants than for dwarfs, but suggest that this
is an unlikely explanation, except perhaps for C, Cr, and Mn. NLTE
computations for Na and Al provide consistent abundances between
dwarfs and giants, unlike the LTE results, and would be highly
desirable for the other discrepant elements as well. Meanwhile, we
recommend using the giant abundances as reference data for Galactic
chemical evolution models.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table7.dat 59 61 Radial velocities of programme giant stars
table1.dat 39 19 Adopted model atmosphere parameters for
unevolved stars
ew.dat 46 1919 Equivalent widths for unevolved stars
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See also:
J/A+A/403/1105 : Extremely metal-poor giants equivalent widths (Francois+ 2003)
J/A+A/416/1117 : Abundances in the early Galaxy (Cayrel+, 2004)
Byte-by-byte Description of file: table7.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Seq [1,35] sequential number of the star
6- 16 A11 --- Name Star name
21- 30 A10 "Y-M-D" Date ? Observation date (1)
36- 48 F13.7 d MJD ? Modified Julian date (JD-2400000.5) of
observation (1)
53- 59 F7.2 km/s RV Barycentric radial velocity
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Note (1): For star #23 see Depagne et al. (2002A&A...390..187D 2002A&A...390..187D),
for star #35 see Hill et al. (2002A&A...387..560H 2002A&A...387..560H)
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Seq [1/19] Sequential number of unevolved stars
4- 15 A12 --- Name Star name
17- 20 I4 K Teff Effective temperature
22- 25 F4.2 [cm/s2] logg Surface gravity
27- 29 F3.1 km/s Vt Microturbulent velocity
31- 35 F5.2 [-] [Fe/H] Metallicity
37- 39 A3 --- Rem Remarks
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Byte-by-byte Description of file: ew.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Seq [1,19] Sequential number
4- 7 A4 --- Ion Ion identification
10- 17 F8.4 nm lambda Wavelength of the line
19- 23 F5.2 eV chi Excitation potential
26- 31 F6.3 --- loggf Logarithm of the oscillator strength
33- 37 F5.2 pm EW ? Equivalent width
38 A1 --- n_EW [s] abundance from spectrum synthesis (1)
39 A1 --- l_AB Limit flag on AB
40- 45 F6.3 --- AB ? Abundance log(N/H)+12
46 A1 --- n_AB [*] not used for mean (2)
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Note (1): 's' (synt) means that the abundance has been obtained by spectrum
synthesis and no EW is provided.
Note (2): an asterisk (*) means the line has not been used to compute the
mean abundance for this star.
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Acknowledgements:
Piercarlo Bonifacio, Piercarlo.Bonifacio(at)obspm.fr
References:
Depagne et al., Paper I 2002A&A...390..187D 2002A&A...390..187D
Hill et al., Paper II 2002A&A...387..560H 2002A&A...387..560H
Francois et al., Paper III 2003A&A...403.1105F 2003A&A...403.1105F Cat. J/A+A/403/1105
Sivarani et al., Paper IV 2004A&A...413.1073S 2004A&A...413.1073S
Cayrel et al., Paper V 2004A&A...416.1117C 2004A&A...416.1117C Cat. J/A+A/416/1117
Spite et al., Paper VI 2005A&A...430..655S 2005A&A...430..655S
Bonifacio et al., Paper VII 2007A&A...462..851B 2007A&A...462..851B
Francois et al., Paper VIII 2007A&A...476..935F 2007A&A...476..935F
Spite et al., Paper IX 2006A&A...455..291S 2006A&A...455..291S
Sivarani et al., Paper X 2006A&A...459..125S 2006A&A...459..125S
Gonzalez Hernandez et al., Paper XI 2008A&A...480..233G 2008A&A...480..233G
History:
* 10-Aug-2009: on-line data
* 02-Apr-2019: table ew.dat corrected (from author)
(End) Patricia Vannier [CDS] 30-Jul-2009