English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

(Abridged) Aims: We study the effects related to departures from non-localthermodynamic equilibrium (NLTE) and homogeneity in the atmospheres of redgiant stars in Galactic globular cluster NGC 6752, to assess their influence onthe formation of Ba II lines. Methods: One-dimensional (1D) local thermodynamicequilibrium (LTE) and 1D NLTE barium abundances were derived using classical 1DATLAS stellar model atmospheres. The three-dimensional (3D) LTE abundances wereobtained for 8 red giants on the lower RGB, by adjusting their 1D LTEabundances using 3D-1D abundance corrections, i.e., the differences between theabundances obtained from the same spectral line using the 3D hydrodynamical(CO5BOLD) and classical 1D (LHD) stellar model atmospheres. Results: The mean1D barium-to-iron abundance ratios derived for 20 giants are <[Ba/Fe]>_{1DNLTE} = 0.05 \pm0.06 (stat.) \pm0.08 (sys.). The 3D-1D abundance correctionobtained for 8 giants is small (~+0.05 dex), thus leads to only minoradjustment when applied to the mean 1D NLTE barium-to-iron abundance ratio forthe 20 giants, <[Ba/Fe]>_{3D+NLTE} = 0.10 \pm0.06(stat.) \pm0.10(sys.). Theintrinsic abundance spread between the individual cluster stars is small andcan be explained in terms of uncertainties in the abundance determinations.Conclusions: Deviations from LTE play an important role in the formation ofbarium lines in the atmospheres of red giants studied here. The role of 3Dhydrodynamical effects should not be dismissed either, even if the obtained3D-1D abundance corrections are small. This result is a consequence of subtlefine-tuning of individual contributions from horizontal temperaturefluctuations and differences between the average temperature profiles in the 3Dand 1D model atmospheres: owing to the comparable size and opposite sign, theircontributions nearly cancel each other.

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