Chemical abundances and kinematics of barium stars

DE CASTRO, D.B.; PEREIRA, C. B.; ROIG, F.; JILINSKI, E.; DRAKE, N. A.;; CHAVERO, C.;; SALES SILVA, J. V.,

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2016 vol. 459 p. 4299 - 4324

0035-8711

In this paper we present an homogeneous analysis of photospheric abundancesbased on high-resolution spectroscopy of a sample of 182 barium stars and candidates.We determined atmospheric parameters, spectroscopic distances, stellar masses,ages, luminosities and scale height, radial velocities, abundances of the Na, Al, alphaelements,iron-peak elements, and s-process elements Y, Zr, La, Ce, and Nd. We employedthe local-thermodynamic-equilibrium model atmospheres of Kurucz and thespectral analysis code moog. We found that the metallicities, the temperatures andthe surface gravities for barium stars can not be represented by a single gaussian distribution.The abundances of alpha-elements and iron peak elements are similar tothose of field giants with the same metallicity. Sodium presents some degree of enrichmentin more evolved stars that could be attributed to the NeNa cycle. As expected,the barium stars show overabundance of the elements created by the s-process. Bymeasuring the mean heavy-element abundance pattern as given by the ratio [s/Fe], wefound that the barium stars present several degrees of enrichment. We also obtainedthe [hs/ls] ratio by measuring the photospheric abundances of the Ba-peak and the Zrpeakelements. Our results indicated that the [s/Fe] and the [hs/ls] ratios are stronglyanti-correlated with the metallicity. Our kinematical analysis showed that 90% of thebarium stars belong to the thin disk population. Based on their luminosities, none ofthe barium stars are luminous enough to be an AGB star, nor to become self-enrichedin the s-process elements. Finally, we determined that the barium stars also follow anage-metallicity relation.