2012A&A...540A.128D


Query : 2012A&A...540A.128D

2012A&A...540A.128D - Astronomy and Astrophysics, volume 540A, 128-128 (2012/4-1)

Barium abundance in red giants of NGC 6752. Non-local thermodynamic equilibrium and three-dimensional effects.

DOBROVOLSKAS V., KUCINSKAS A., ANDRIEVSKY S.M., KOROTIN S.A., MISHENINA T.V., BONIFACIO P., LUDWIG H.-G. and CAFFAU E.

Abstract (from CDS):

We study the effects related to departures from non-local thermodynamic equilibrium (NLTE) and homogeneity in the atmospheres of red giant stars, to assess their influence on the formation of Ba II lines. We estimate the impact of these effects on the barium abundance determinations for 20 red giants in Galactic globular cluster NGC 6752. One-dimensional (1D) local thermodynamic equilibrium (LTE) and 1D NLTE barium abundances were derived using classical 1D ATLAS9 stellar model atmospheres. The three-dimensional (3D) LTE abundances were obtained for 8 red giants on the lower RGB, by adjusting their 1D LTE abundances using 3D-1D abundance corrections, i.e., the differences between the abundances obtained from the same spectral line using the 3D hydrodynamical and classical 1D stellar model atmospheres. The 3D-1D abundance corrections were obtained in a strictly differential way using the 3D hydrodynamical and classical 1D codes CO5BOLD and LHD. Both codes utilized identical stellar atmospheric parameters, opacities, and equation of state. The mean 1D barium-to-iron abundance ratios derived for 20 giants are <[Ba/Fe]>1D–LTE=0.24±0.05(stat.)±0.08(sys.) and <[Ba/Fe]>1D–NLTE=0.05±0.06(stat.)±0.08(sys.). The 3D-1D abundance correction obtained for 8 giants is small (~+0.05dex), thus leads to only minor adjustment when applied to the mean 1D NLTE barium-to-iron abundance ratio for the 20 giants, <[Ba/Fe]>3D+NLTE=0.10±0.06(stat.)±0.10(sys.). The intrinsic abundance spread between the individual cluster stars is small and can be explained in terms of uncertainties in the abundance determinations. Deviations from LTE play an important role in the formation of barium lines in the atmospheres of red giants studied here. The role of 3D hydrodynamical effects should not be dismissed either, even if the obtained 3D-1D abundance corrections are small. This result is a consequence of subtle fine-tuning of individual contributions from horizontal temperature fluctuations and differences between the average temperature profiles in the 3D and 1D model atmospheres: owing to the comparable size and opposite sign, their contributions nearly cancel each other. This fine-tuning is characteristic of the particular set of atmospheric parameters and the element investigated, hence should not necessarily be a general property of spectral line formation in the atmospheres of red giant stars.

Abstract Copyright:

Journal keyword(s): stars: late-type - stars: abundances - stars: atmospheres - globular clusters: individual: NGC6752 - techniques: spectroscopic

Simbad objects: 27

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Number of rows : 27
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 NGC 5139 GlC 13 26 47.28 -47 28 46.1   6.12 5.33     ~ 3252 0
2 M 10 GlC 16 57 09.05 -04 06 01.1     4.98     ~ 745 0
3 M 92 GlC 17 17 07.39 +43 08 09.4     6.52     ~ 2001 0
4 M 54 GlC 18 55 03.33 -30 28 47.5           ~ 1003 0
5 Cl* NGC 6752 BUON 4446 * 19 10 14.9559748296 -59 59 13.414731468   14.59 13.78     ~ 10 0
6 Cl* NGC 6752 YGN 29 * 19 10 16.6112031624 -60 00 59.767765308     14.18     ~ 5 0
7 Cl* NGC 6752 BUON 4216 RG* 19 10 19.5305698584 -60 00 30.156575040   14.520 13.698     ~ 10 0
8 NGC 6752 67 RG* 19 10 25.9459355640 -59 59 05.050889808   14.38 13.59     ~ 11 0
9 Cl* NGC 6752 YGN 6 * 19 10 34.3616645352 -59 59 55.028925744   14.43 13.40     ~ 6 0
10 NGC 6752 57 RG* 19 10 36.4928689368 -59 56 07.703392560   14.62 14.00     ~ 11 0
11 Cl* NGC 6752 YGN 30 * 19 10 38.8613425608 -59 59 47.296470264     14.19     ~ 8 0
12 Cl* NGC 6752 CBG 14537 RG* 19 10 43.802 -59 59 41.65   14.913 14.135     ~ 10 0
13 Cl* NGC 6752 BUON 3103 * 19 10 45 -59 58.3     13.56     ~ 7 0
14 Cl* NGC 6752 YGN 1 * 19 10 47 -60 00.7     13.27     ~ 6 0
15 NGC 6752 5 RG* 19 10 48.6380923344 -60 01 55.414478928   14.402 13.743 13.633   ~ 12 0
16 Cl* NGC 6752 BUON 2728 RG* 19 10 49.9412104080 -60 02 25.640269368   14.528 13.697     ~ 10 0
17 NGC 6752 GlC 19 10 52.11 -59 59 04.4   6.96 6.28     ~ 1902 0
18 Cl* NGC 6752 YGN 7 * 19 10 56.6307863736 -60 00 41.575798368   14.30 13.46     ~ 5 0
19 Cl* NGC 6752 YGN 3 * 19 10 59.6123988384 -59 56 40.510533516   14.27 13.35     ~ 6 0
20 2MASS J19111115-6000169 RG* 19 11 11.1684637896 -60 00 16.942232952   14.07 13.33     ~ 12 0
21 NGC 6752 37 RG* 19 11 11.6425951848 -59 58 28.749173376   14.89 14.08     ~ 12 0
22 NGC 6752 17 RG* 19 11 13.4059513224 -60 02 30.244768548   14.85 14.06     ~ 12 0
23 NGC 6752 32 RG* 19 11 18.5097639600 -59 59 41.691616980   14.58 13.63     ~ 10 0
24 Cl* NGC 6752 BUON 1113 RG* 19 11 23.1147114120 -59 59 39.720399864   14.815 14.002     ~ 11 0
25 2MASS J19113265-6000021 RG* 19 11 32.6634739224 -60 00 02.105715024   14.322 13.491     ~ 10 0
26 M 71 GlC 19 53 46.49 +18 46 45.1   7.91 6.1     ~ 1076 0
27 M 15 GlC 21 29 58.33 +12 10 01.2   3       ~ 3029 0

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2022.08.13-02:59:42

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