Abstract
Using an Non-Local Thermodynamic Equilibrium (NLTE) analysis and a homogenous spectral data base, we have determined Ba abundances in a sample of 210 Galactic Cepheids and related objects. We confirm the previous result reported in Andrievsky et al. that the barium distribution in the range of Galactocentric distances from 5 to 18 kpc shows very small gradient value. The value determined here – d[Ba/H]/dR ≈ −0.01 dex kpc−1 – is smaller than that for other s-process elements, such as La, Pr, Nd and Sm (Luck & Lambert), that typically show gradients of −0.03 dex kpc−1.
Highlights
Barium is an element whose primary source is the main s-process in asymptotic giant branch (AGB) stars
In Andrievsky et al (2013), we determined Non-Local Thermodynamic Equilibrium (NLTE) barium abundances in a sample of 270 Cepheids distributed at Galactocentric distances from 4 to 15 kpc
We found the rather unexpected result that the barium abundance distribution does not show any significant slope; that is, the barium radial Galactocentric abundance gradient is about zero
Summary
Barium is an element whose primary source is the main s-process in asymptotic giant branch (AGB) stars. This contrasts with α- and iron peak elements that derive from supernovae. We found the rather unexpected result that the barium abundance distribution does not show any significant slope; that is, the barium radial Galactocentric abundance gradient is about zero. This result contrasts with the previous finding for other s/r-process elements, which shows the gradient for those elements is small, but non-zero (Luck & Lambert 2011). It is important to check our previous finding with an extended sample of stars, and this is the main aim of our present study
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