J/A+A/628/A54 Fe, Mg, Ti in Galactic clusters (Kovalev+, 2019)
NLTE Chemical abundances in Galactic open and globular clusters.
Kovalev M., Bergemann M., Ting Y.-S., Rix H.-W.
<Astron. Astrophys. 628, A54 (2019)>
=2019A&A...628A..54K 2019A&A...628A..54K (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Clusters, globular ; Clusters, open ; Abundances
Keywords: stars: abundances: abundances - stars: fundamental parameters -
techniques: spectroscopic - open clusters and associations: general -
globular clusters: general
Abstract:
We test the effects of non-local thermodynamic equilibrium (NLTE) on
the spectra of FGK-type stars across a wide range of metallicity and
to derive abundance of Fe, Mg, and Ti for a sample of Galactic star
clusters.
We extend the Payne fitting approach to draw on NLTE and LTE spectral
models in order to determine stellar parameters and chemical
abundances for the Gaia-ESO benchmark stars. We also analyse the
medium-resolution Giraffe spectra of 742 stars in 13 open and globular
clusters in the Milky Way galaxy.
We show that this approach accurately recovers effective temperatures,
surface gravities, and abundances of the benchmark stars and clusters
members. The differences between NLTE and LTE stellar parameters are
small for the metal-rich stars. However, for metal-poor stars
[Fe/H]←1, the NLTE estimates of Teff, log(g) and [Fe/H] are higher
than LTE estimates, and the systematic offset increases with
decreasing metallicity. Our LTE measurements of metallicities and
abundances in the Galactic clusters are in a good agreement with the
earlier literature studies. For the majority of these clusters, our
study yields the first estimates of NLTE abundances of Fe, Mg and Ti.
The NLTE [Fe/H] are systematically higher, whereas the average NLTE
[Mg/Fe] abundance ratios are ∼0.15dex lower, compared to LTE. All
clusters investigated in this work appear homogeneous in Fe and Ti,
with the intra-cluster abundance variations of less then 0.1dex. We
confirm large dispersions of [Mg/Fe] ratios for NGC 2808, NGC 4833 and
M 15. Our results shows that NLTE analysis change the mean abundance
ratios in the clusters, but does not influence the intra-cluster
abundance dispersions.
Combining the Payne fitting approach with NLTE spectral models as
input is a powerful tool for a detailed exploration of the large-scale
spectroscopic stellar surveys.
Description:
We investigated the abundances of four elements Fe, Mg, Ti, Mn for 742
stars in 13 open and globular clusters (NGC 3532, NGC 2243,
NGC 5927,NGC 104, NGC 1851, NGC 2808, NGC 362, NGC 6752, NGC 1904,
NGC 4833, NGC 4372, M 2, M 15) using Gaia-ESO HR10 spectra. The
abundances are derived by spectral fitting with the automatic code
Payne (Ting, 2018,arxiv:1804.01530), which uses NLTE/LTE spectral
models from http://nlte.mpia.de.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea5.dat 151 742 Abundances of four elements Fe, Mg, Ti, Mn for
742 stars in 13 open and globular clusters
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Byte-by-byte Description of file: tablea5.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- Star Star name (HHMMSSss+DDMMSSs)
18- 25 A8 --- Cluster Cluster name
27- 31 F5.1 --- SNR Signal-to-noise ratio
34- 37 I4 K TeffN NLTE effective temperature
40- 43 I4 K TeffL LTE effective temperature
45- 48 F4.2 [cm2/s] loggN NLTE gravity surface
50- 53 F4.2 [cm2/s] loggL LTE gravity surface
55- 58 F4.2 km/s vmicN NLTE microturbulent velocity
60- 63 F4.2 km/s vmicL LTE microturbulent velocity?
65- 69 F5.2 [-] [Fe/H]N NLTE [Fe/H] abundance
71- 75 F5.2 [-] [Fe/H]L LTE [Fe/H] abundance
77- 80 F4.2 [-] e_[Fe/H]N rms uncertainty on NLTE [Fe/H] abundance
82- 85 F4.2 [-] e_[Fe/H]L rms uncertainty on LTE [Fe/H] abundance
87- 91 F5.2 [-] [Mg/Fe]N NLTE [Mg/H] abundance
93- 97 F5.2 [-] [Mg/Fe]L LTE [Mg/H] abundance
99-102 F4.2 [-] e_[Mg/Fe]N rms uncertainty on NLTE [Mg/H] abundance
104-107 F4.2 [-] e_[Mg/Fe]L rms uncertainty on LTE [Mg/H] abundance
109-113 F5.2 [-] [Ti/Fe]N NLTE [Ti/H] abundance
115-119 F5.2 [-] [Ti/Fe]L LTE [Ti/H] abundance
121-124 F4.2 [-] e_[Ti/Fe]N rms uncertainty on NLTE [Ti/H] abundance
126-129 F4.2 [-] e_[Ti/Fe]L rms uncertainty on LTE [Ti/H] abundance
131-135 F5.2 [-] [Mn/Fe]N NLTE [Mn/H] abundance
137-141 F5.2 [-] [Mn/Fe]L LTE [Mn/H] abundance
143-146 F4.2 [-] e_[Mn/Fe]N rms uncertainty on NLTE [Mn/H] abundance
148-151 F4.2 [-] e_[Mn/Fe]L rms uncertainty on LTE [Mn/H] abundance
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Acknowledgements:
M. Kovalev, kovalev(at)mpia.de
(End) Patricia Vannier [CDS] 02-Jul-2019