J/A+A/604/A35 NGC104 RGB Na, Mg, and K abundances (Cerniauskas+, 2017)
Abundances of Na, Mg, and K in the atmospheres of RGB stars of Galactic globular
cluster 47 Tucanae.
Cerniauskas A., Kucinskas A., Klevas J., Prakapavicius D., Korotin S.,
Bonifacio P., Ludwig H.-G., Caffau E., Steffen M.
<Astron. Astrophys. 604, A35 (2017)>
=2017A&A...604A..35C 2017A&A...604A..35C (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Stars, late-type - Stars, giant ;
Abundances
Keywords: globular clusters: individual: NGC 104 - stars: late type -
stars: atmospheres - stars: abundances - techniques: spectroscopic -
convection
Abstract:
We study the abundances of Na, Mg, and K in the atmospheres of 32 red
giant branch (RGB) stars in the Galactic globular cluster (GGC) 47
Tuc, with the goal to investigate the possible existence of Na-K and
Mg-K correlations/anti-correlations, similar to those that were
recently discovered in two other GGCs, NGC 2419 and 2808.
The abundances of K, Na, and Mg were determined using high-resolution
2df spectra obtained with the Anglo-Australian Telescope (AAT). The 1D
NLTE abundance estimates were obtained using 1D hydrostatic ATLAS9
model atmospheres and spectral line profiles synthesized with the
MULTI package. We also used 3D hydrodynamical CO5BOLD and 1D
hydrostatic LHD model atmospheres to compute 3D-1D LTE abundance
corrections, Delta 3D-1D LTE, for the spectral lines of Na, Mg, and K
used in our study. These abundance corrections were used to understand
the role of convection in the formation of spectral lines, as well as
to estimate the differences in the abundances obtained with the 3D
hydrodynamical and 1D hydrostatic model atmospheres.
The average element-to-iron abundance ratios and their RMS variations
due to star-to-star abundance spreads determined in our sample of RGB
stars were <[Na/Fe]>(1D-NLTE)=0.42±0.13,
<[Mg/Fe]>(1D-NLTE)=0.41±0.11, and <[K/Fe]>(1D-NLTE)=0.05±0.14.
We found no statistically significant relations between the abundances
of the three elements studied here. Also, there were no abundance
trends with the distance from the cluster center, nor any
statistically significant relations between the abundance/abundance
ratios and absolute radial velocities of individual stars. All these
facts suggest the similarity of K abundance in stars that belong to
different generations in 47 Tuc which, in turn, may hint that
evolution of K in this particular cluster was unrelated to the
nucleosynthesis of Na and/or Mg.
Description:
We used 2dF/HERMES spectra obtained in two wavelength regions,
564.9-587.3nm (GREEN) and 758.5-788.7nm (IR), using the spectral
resolution of R∼28000 and exposure time of 1200s. The observations
were carried out during the period of Oct 22 - Dec 20, 2013
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 87 32 Target RGB stars in 47 Tuc, their atmospheric
parameters, and determined abundances of
Na, Mg and K
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See also:
J/A+A/435/657 : Equivalent widths of 5 giants in 47 Tuc (Alves-Brito+, 2005)
J/A+A/549/A41 : Horizontal branch stars in 47 Tuc and M5 (Gratton+, 2013)
J/A+A/550/A34 : Abundances of red giants in M4 and 47 Tuc (Carretta+, 2013)
J/A+A/565/A121 : Abundances of 47 Tuc turn-off stars (Dobrovolskas+, 2014)
J/A+A/572/A108 : 47 Tuc red giants chemical composition (Thygesen+, 2014)
J/ApJ/780/94 : Abundances of red giants in 47 Tuc (Cordero+, 2014)
J/ApJ/797/124 : AGB and RGB stars in 47 Tuc (Lapenna+, 2014)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- ID Star name (N104-SNNNN)
12- 18 F7.5 deg RAdeg Right ascension (J2000)
20- 28 F9.5 deg DEdeg Declination (J2000)
30- 34 F5.2 mag Vmag [12.99/14.25] V magnitude
36- 40 F5.2 mag Imag [11.75/13.17] I magnitude
42- 45 I4 K Teff [4390/4720] Effective temperature
47- 50 F4.2 [cm/s2] logg [1.6/2.3] Surface gravity
52- 56 F5.1 [km/s] RV Radial velocity
58- 61 F4.2 [-] [Na/Fe] ? 1D NLTE sodium abundance (1)
63- 66 F4.2 [-] e_[Na/Fe] ? Error of sodium abundance
68- 71 F4.2 [-] [Mg/Fe] ? 1D NLTE magnesium abundance (1)
73- 76 F4.2 [-] e_[Mg/Fe] ? Error of magnesium abundance
78- 82 F5.2 [-] [K/Fe] ? 1D NLTE potassium abundance (1)
84- 87 F4.2 [-] e_[K/Fe] ? Error of potassium abundance
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Note (1): The abundances were derived assuming identical microturbulence
velocity of 1.5km/s for all stars; A(H)=12.4.
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Acknowledgements:
algimantas.cerniauskas(at)tfai.vu.lt
(End) Patricia Vannier [CDS] 31-Mar-2017