J/A+A/660/A46 Abundance of zirconium in 47 Tuc (Kolomiecas+, 2022)
Abundance of zirconium in the globular cluster 47 Tuc:
a possible Zr-Na correlation?
Kolomiecas E., Dobrovolskas V., Kucinskas A., Bonifacio P., Korotin S.
<Astron. Astrophys. 660, A46 (2022)>
=2022A&A...660A..46K 2022A&A...660A..46K
ADC_Keywords: Clusters, globular ; Stars, dwarfs ; Abundances ; Optical
Keywords: techniques: spectroscopic - stars: abundances - stars: late-type -
globular clusters: individual: 47 Tuc
Abstract:
We determined abundances of Na and Zr in the atmospheres of 237 RGB
stars in Galactic globular cluster (GGC) 47 Tuc (NGC 104), with a
primary goal of searching for possible differences between the
abundances of Zr in the first generation (1P) and second generation
(2P) stars. For the abundance analysis, we used archival UVES/GIRAFFE
spectra obtained during three different observing programmes.
Abundances were determined from two NaI and three ZrI lines, using
1D hydrostatic ATLAS9 model atmospheres. The target stars for the
abundance analysis were limited to those with 4200≤Teff≤4800K.
This is the largest sample of GGC stars in which Na and Zr abundances
have been studied so far. While our mean [Na/Fe] and [Zr/Fe] ratios
agree well with those determined in the earlier studies, we find a
weak but statistically significant correlation in the
[Zr/Fe]-[Na/Fe] plane. A comparison of the mean [Zr/Fe] abundance
ratios in the 1P and 2P stars suggests a small but statistically
significant Zr over-abundance in the 2P stars,
{DELTA}[Zr/Fe]2P-1P~=+0.06 dex. Also, our analysis shows that stars
enriched in both Zr and Na are more centrally concentrated. However,
we find no correlation between their distance from the cluster centre
and their full spatial velocity, as indicated by the velocity
dispersions at different mean values of [Zr/Fe] and [Na/Fe]. While
there may be some influence of CN line blends on the determined Zr
abundances, it seems very unlikely that the detected Zr-Na
correlation, as well as the slightly higher Zr abundances in the 2P
stars, would be caused by the CN blending alone.
The obtained results indicate that, in 47 Tuc, some amount of Zr
should have been synthesised by the same polluters that enriched 2P
stars with the light elements. Unfortunately, our data alone do not
allow us to distinguish which of the two scenarios, or whether or not
a combination of both, could have operated in this GGC.
Description:
Spectra of the RGB stars in 47 Tuc investigated in this work were
obtained with the GIRAFFE spectrograph under the programmes:
072.D-0777(A) (PI: P. Francois); 073.D-0211(A) (PI: E. Carretta);
088.D-0026(A) (PI: I. McDonald).
We present determined effective temperatures and gravities of the
target stars.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tabled1.dat 105 282 Determined effective temperatures and gravities
of the target stars
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See also:
I/350 : Gaia EDR3 (Gaia Collaboration, 2020)
Byte-by-byte Description of file: tabled1.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- GaiaEDR3 GAIA EDR3 identification number
21- 24 I4 K Teff Effective temperature
26- 29 F4.2 [cm/s2] logg Surface gravity
31- 34 F4.2 km/s vmic Microturbulence velocity
36- 39 F4.2 --- A(Fe) 1D LTE iron abundance
41- 45 F5.2 --- [Fe/H] Iron-to-hydrogen ratio
47- 50 F4.2 --- A(Na) 1D NLTE sodium abundance
52- 55 F4.2 --- [Na/Fe] Sodium-to-iron ratio
57- 60 F4.2 --- A(Zr) 1D LTE zirconium abundance
62- 65 F4.2 --- [Zr/Fe] Zirconium-to-iron ratio
67- 73 A7 --- ID Identification number in a given observing
programme
75- 87 A13 --- ObsProg Observing programme
89- 96 F8.6 deg RAdeg Right ascension (J2000)
98-105 F8.4 deg DEdeg Declination (J2000)
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Acknowledgements:
Edgaras Kolomiecas, edgaras.kolomiecas(at)ff.vu.lt
(End) Patricia Vannier [CDS] 20-Nov-2021