J/A+A/679/A110 Titans metal-poor reference stars. II. (Giribaldi+, 2023)
Titans metal-poor reference stars. II. Red giants and CEMP stars.
Giribaldi R.E., Van Eck S., Merle T., Jorissen A., Krynski P., Planquart L.,
Valentini M., Chiappini C., Van Winckel H.
<Astron. Astrophys. 679, A110 (2023)>
=2023A&A...679A.110G 2023A&A...679A.110G (SIMBAD/NED BibCode)
ADC_Keywords: Stars, metal-deficient ; Stars, giant ; Effective temperatures ;
Abundances, [Fe/H] ; Stars, diameters
Keywords: surveys - techniques: spectroscopic - stars: atmospheres -
stars: fundamental parameters - stars: Population II - stars: carbon
Abstract:
Representative samples of F-, G-, K-type stars located out of the
Solar Neighbourhood has started to be available in spectroscopic
surveys. The fraction of metal-poor ([Fe/H]≤-0.8dex) giants becomes
increasingly relevant to far distances. In metal-poor stars, effective
temperatures (Teff) based on LTE spectroscopy and on former
colour-Teff relations of still wide use have been reported to be
inaccurate. It is necessary to re-calibrate chemical abundances based
on these Teff scales in the multiple available surveys to bring them
to the same standard scale for their simultaneous use. For that, a
complete sample of standards is required, which so far, is restricted
to a few stars with quasi-direct Teff measurements.
We aim at providing a legacy sample of metal-poor standards with
proven accurate atmospheric parameters. We add 47 giants to the sample
of metal-poor dwarfs of Giribaldi et al. (2021A&A...650A.194G 2021A&A...650A.194G, Cat.
J/A+A/650/A194), thereby constituting the Titans metal-poor reference
stars.
Teff was derived by 3D non-LTE Hα modelling, whose accuracy was
tested against interferometry and InfraRed Flux Method (IRFM). Surface
gravity (logg) was derived by fitting MgI b triplet lines, whose
accuracy was tested against asteroseismology. Metallicity was derived
using FeII lines, which was verified to be identical to the [Fe/H]
derived from non-LTE spectral synthesis.
Teff from 3D non-LTE Hα is equivalent to interferometric and IRFM
temperatures within a ±46K uncertainty. We achieved precision of
∼50K for 34 stars with spectra with the highest S/N. For log g, we
achieved a total uncertainty of ±0.15dex. For [Fe/H], we obtained a
total uncertainty of ±0.09dex. We find that the ionization
equilibrium of Fe lines under LTE is not valid in metal-poor giants.
LTE leads to a small but significant metallicity underestimation of
∼0.1dex when derived from weak FeI lines, only provided accurate
Teff and logg. This bias disappears totally under non-LTE.
Description:
We provide accurate fundamental parameters and Mg abundances of the
TITANS II standard stars. This table complements the TITANS I sample
in Giribaldi et al., 2021A&A...650A.194G 2021A&A...650A.194G, Cat. J/A+A/650/A194 (DOI:
10.1051/0004-6361/202140751).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 98 47 Determined atmospheric parameters of the giant Titans
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See also:
J/A+A/650/A194 : Titans metal-poor reference stars. I. (Giribaldi+, 2021)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- Name Simbad star name
18- 21 I4 K Teff ? Effective temperature
23- 25 I3 K e_Teff ? Error of Effective temperature
27- 30 I4 K Teff2 ? Effective temperature derived by other
method compatible with accurate Teff
32- 33 I2 K e_Teff2 ? Error of effective temperature derived by
other method compatible with accurate Teff
35- 38 F4.2 [cm/s2] logg Surface gravity
40- 43 F4.2 [cm/s2] e_logg ? Error of surface gravity
45- 49 F5.2 [-] [FeI/H] Metallicity from neutral iron in LTE
51- 54 F4.2 [-] e_[FeI/H] Error of metallicity from neutral iron in LTE
56- 60 F5.2 [-] [FeII/H] ? Metallicity from ionised iron in non-LTE
62- 65 F4.2 [-] e_[FeII/H] ? Error of metallicity from ionised iron
in non-LTE
67- 71 F5.3 [Lsun] logL ? Luminosity relative to solar
73- 77 F5.3 [Lsun] e_logL ? Error of Luminosity relative to solar
79- 83 F5.2 Rsun Rad ? Radius relative to solar
85- 88 F4.2 Rsun e_Rad ? Error of radius relative to solar
90- 93 F4.2 [-] A(Mg) ? Magnesium abundance
95- 98 F4.2 [-] e_A(Mg) ? Error of magnesium abundance
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Acknowledgements:
Riano Giribaldi, rianoesc(at)gmail.com
References:
Giribaldi et al., Paper I 2021A&A...650A.194G 2021A&A...650A.194G, Cat. J/A+A/650/A194
(End) Patricia Vannier [CDS] 24-Oct-2023