J/A+A/620/A187 Very metal-poor turn-off stars abundances (Francois+, 2018)
TOPoS. V: Abundance ratios in a sample of very metal-poor turn-off stars.
Francois P., Caffau E., Bonifacio P., Spite M., Spite F., Cayrel R.,
Christlieb N., Gallagher A., Klessen R., Koch A., Ludwig H.-G., Monaco L.,
Plez B., Steffen M., Zaggia S.
<Astron. Astrophys. 620, A187 (2018)>
=2018A&A...620A.187F 2018A&A...620A.187F (SIMBAD/NED BibCode)
ADC_Keywords: Stars, metal-deficient ; Abundances ; Milky Way
Keywords: stars: abundances - Galaxy: abundances
Abstract:
Extremely metal-poor stars are keys to understand the early evolution
of our Galaxy. The ESO large programme TOPoS has been tailored to
analyse a new set of metal-poor turn-off stars, whereas most of the
previously known extremely metal-poor stars are giant stars.
Our results confirms the super-solar [Mg/Fe] and [Ca/Fe] ratios in
metal-poor turn-off stars as observed in metal-poor giant stars. We
found a significant spread of the [alpha/Fe] ratios with several stars
showing sub-solar [Ca/Fe] ratios. We could measure the abundance of
strontium in 12 stars of the sample, leading to abundance ratios
[Sr/Fe] around the Solar value. We detected barium in two stars of the
sample. One of the stars (SDSS J114424-004658) shows both very high
[Ba/Fe] and [Sr/Fe] abundance ratios (>1dex).
Description:
Sixty five turn-off stars (preselected from SDSS spectra) have been
observed with the X-Shooter spectrograph at the ESO VLT Unit
Telescope 2, to derive accurate and detailed abundances of magnesium,
silicon, calcium, iron, strontium and barium. We analysed
medium-resolution spectra (R∼10000) obtained with the ESO X-Shooter
spectrograph and computed the abundances of several alpha and
neutron-capture elements using standard one-dimensional local
thermodynamic equilibrium (1D LTE) model atmospheres.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 89 65 Stellar Parameters
tablea2.dat 83 65 Chemical composition of the stars analysed in
this paper
tablea3.dat 31 1006 Equivalent width of Fe lines used to determine
the metallicity of the stars
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See also:
J/A+A/579/A28 : Abundances of 3 CEMP stars (Bonifacio+, 2015)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- SDSS SDSS star identification (JHHMMSS+DDMMSS)
17- 20 I4 K Teff Effective temperature
23- 27 F5.2 [-] [Fe/H] Metallicity
30- 31 I2 h RAh Right ascension (J2000.0)
33- 34 I2 min RAm Right ascension (J2000.0)
36- 40 F5.2 s RAs Right ascension (J2000.0)
42 A1 --- DE- Declination sign (J2000.0)
43- 44 I2 deg DEd Declination (J2000.0)
46- 47 I2 arcmin DEm Declination (J2000.0)
49- 52 F4.1 arcsec DEs Declination (J2000.0)
54- 60 F7.4 mag Gmag Gaia G magnitude
63- 64 I2 --- SNR Signal to Noise ratio
66- 89 A24 --- Name SDSS DR12 name (SDSS JHHMMSS.ss+DDMMSS.s)
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Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- SDSS SDSS star identification (JHHMMSS+DDMMSS)
18- 22 F5.2 [-] [Fe/H] Metallicity
25 A1 --- l_A(C) Upper limit flag on A(C)
26- 29 F4.2 [-] A(C) Carbon abundance (upper limit)
32- 36 F5.2 [-] [Mg/Fe] ? Abundance [Mg/Fe]
39 I1 --- nMg ? Number of lines used to determine the
abundance of Mg
42- 46 F5.2 [-] [Ca/Fe] ? Abundance [Ca/Fe]
51 I1 --- nCa ? Number of lines used to determine the
abundance of Ca
53- 57 F5.2 [-] [Si/Fe] ? Abundance [Si/Fe]
61 I1 --- nSi ? Number of lines used to determine the
abundance of Si
64- 68 F5.2 [-] [Sr/Fe] ? Abundance [Sr/Fe]
72 I1 --- nSr ? Number of lines used to determine the
abundance of Sr
75- 79 F5.2 [-] [Ba/Fe] ? Abundance [Ba/Fe]
83 I1 --- nBa ? Number of lines used to determine the
abundance of Ba
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Byte-by-byte Description of file: tablea3.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- SDSS SDSS star identification (JHHMMSS+DDMMSS)
17- 18 A2 --- El Element
20- 27 F8.4 nm Lambda Wavelength
29- 31 I3 0.1pm EW Equivalent width (mÅ)
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Acknowledgements:
Patrick Francois, patrick.francois(at)obspm.fr
References:
Caffau et al., Paper I 2013A&A...560A..71C 2013A&A...560A..71C
Bonifacio et al., Paper II 2015A&A...579A..28B 2015A&A...579A..28B, Cat. J/A+A/579/A28
Caffau et al., Paper III 2016A&A...595L...6C 2016A&A...595L...6C
Bonifacio et al., Paper IV 2018A&A...612A..65B 2018A&A...612A..65B
(End) Patrick Francois [Paris Observatory], Patricia Vannier [CDS] 05-Nov-2018