J/ApJ/847/142 Ultra-metal-poor stars LTE and NLTE abundances (Ezzeddine+, 2017)
Ultra-metal-poor stars: spectroscopic determination of stellar atmospheric
parameters using iron non-LTE line abundances.
Ezzeddine R., Frebel A., Plez B.
<Astrophys. J., 847, 142 (2017)>
=2017ApJ...847..142E 2017ApJ...847..142E
ADC_Keywords: Abundances, [Fe/H]; Stars, metal-deficient; Equivalent widths;
Models
Keywords: line: formation ; stars: abundances ; stars: atmospheres ;
stars: fundamental parameters ; stars: Population II
Abstract:
We present new ultra-metal-poor stars parameters with [Fe/H] < -4.0
based on line-by-line non-local thermodynamic equilibrium (NLTE)
abundances using an up-to-date iron model atom with a new recipe for
non-elastic hydrogen collision rates. We study the departures from LTE
in their atmospheric parameters and show that they can grow up to
∼1.00dex in [Fe/H], ∼150K in Teff and ∼0.5dex in logg toward the
lowest metallicities. Accurate NLTE atmospheric stellar parameters, in
particular [Fe/H] being significantly higher, are the first step to
eventually providing full NLTE abundance patterns that can be compared
with Population III supernova nucleosynthesis yields to derive
properties of the first stars. Overall, this maximizes the potential
of these likely second-generation stars to investigate the early
universe and how the chemical elements were formed.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 62 631 Atomic linelists and obtained FeI and FeII
abundances of the ultra-metal-poor stars
table3.dat 99 20 *Our results for the average FeI, FeII, and total
Fe abundances with their standard deviation errors
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Note on table3.dat: Values are reported relative to the solar iron abundance of
ε(Fe)☉=7.50 from Asplund+ (2009ARA&A..47..481A 2009ARA&A..47..481A).
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See also:
J/AJ/103/1987 : Stars of very low metal abundance (Beers+ 1992)
J/A+A/275/101 : Chemical evolution of the galactic disk I. (Edvardsson+ 1993)
J/A+A/416/1117 : Abundances in the early Galaxy (Cayrel+, 2004)
J/ApJ/769/57 : Equivalent widths of metal-poor stars (Frebel+, 2013)
J/ApJ/762/25 : The most metal-poor stars in HES and SDSS. I. (Norris+, 2013)
J/A+A/572/A103 : Inelastic silicon-hydrogen collision data (Belyaev+, 2014)
J/A+A/564/A133 : Gaia FGK benchmark stars: metallicity (Jofre+, 2014)
J/AJ/147/136 : Stars of very low metal abundance. VI. (Roederer+, 2014)
J/A+A/579/A28 : Abundances of 3 CEMP stars (Bonifacio+, 2015)
J/ApJS/216/1 : New FeI level energies from stellar spectra (Peterson+, 2015)
J/A+A/587/A114 : Inelastic calcium-hydrogen collision data (Belyaev+, 2016)
J/A+A/586/A120 : Grid of 1D models for Mg line formation (Osorio+, 2016)
J/A+A/593/A27 : Inelastic beryllium-hydrogen collision data (Yakovleva+, 2016)
J/ApJ/833/225 : -2.6≤[Fe/H]≤0.2 F and G dwarfs. II. Abundances (Zhao+, 2016)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- Name Star name
17- 20 A4 --- Ion Species identifier
22- 29 F8.3 0.1nm lambda [3255.8/5586.8] Wavelength λ;
in Angstroms unit
31- 35 F5.3 eV ExPot [0/4.4] Excitation potential
37- 41 F5.2 [-] log(gf) [-4.8/0.7] Log of the oscillator strength
44- 44 A1 --- l_EW Limit flag on EW
45- 49 F5.1 10-13m EW [0.8/143] Equivalent width of line,
in milli-Angstroms unit
51- 51 A1 --- l_logeLTE Limit flag on loge-LTE
52- 55 F4.2 [-] logeLTE [0.2/4.1] logε abundance of line, LTE
57- 57 A1 --- l_logeNLTE Limit flag on loge-NLTE
58- 62 F5.3 [-] logeNLTE [0.9/4.7] logε abundance of line, NLTE
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1 I1 --- Group [1/3] Ultra-metal-poor star group (1)
3- 17 A15 --- Name Star name
19 A1 --- f_Name [bc] Flag on Name (2)
21 A1 --- l_[FeI/H] Limit flag on [FeI/H]
22- 26 F5.2 [Sun] [FeI/H] LTE FeI abundance
28- 31 F4.2 [Sun] e_[FeI/H] [0.07/0.3]? Uncertainty on [FeI/H]
33 A1 --- l_[FeII/H] Limit flag on [FeI/H]
34- 38 F5.2 [Sun] [FeII/H] ? LTE FeII abundance
40- 43 F4.2 [Sun] e_[FeII/H] [0.08/0.2]? Uncertainty on [FeII/H]
45 A1 --- l_[FeI/H]n Limit flag on [FeI/H]
46- 50 F5.2 [Sun] [FeI/H]n non-LTE FeI abundance
52- 55 F4.2 [Sun] e_[FeI/H]n [0.03/0.2]? Uncertainty on [FeI/H]n
57 A1 --- l_[FeII/H]n Limit flag on [FeI/H]
58- 62 F5.2 [Sun] [FeII/H]n ? non-LTE FeII abundance
64- 67 F4.2 [Sun] e_[FeII/H]n [0.07/0.2]? Uncertainty on [FeII/H]n
69 A1 --- l_[Fe/H] Limit flag on [FeI/H]
70- 74 F5.2 [Sun] [Fe/H] LTE total Fe abundance
76- 79 F4.2 [Sun] e_[Fe/H] [0.07/0.3]? Uncertainty on [Fe/H]
81 A1 --- l_[Fe/H]n Limit flag on [FeI/H]
82- 86 F5.2 [Sun] [Fe/H]n non-LTE total Fe abundance
88- 91 F4.2 [Sun] e_[Fe/H]n [0.03/0.2]? Uncertainty on [Fe/H]n
93- 95 I3 --- NFeI Number of FeI lines used
96 A1 --- n_NFeI a: No line detection, upper limit only
98- 98 I1 --- NFeII Number of FeII lines used
99 A1 --- n_NFeII a: No line detection, upper limit only
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Note (1): Group as follows:
1 = -4.5 < [Fe/H] < -4.0
2 = -5.0 < [Fe/H] < -4.5
3 = [Fe/H] < -5.0
Note (2):
b = uncertainties of 1σ
c = uncertainties of 3σ
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 07-Jun-2018