Volume 525, January 2011
|Number of page(s)||16|
|Published online||01 December 2010|
Mn, Cu, and Zn abundances in barium stars and their correlations with neutron capture elements⋆,⋆⋆,⋆⋆⋆
Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de
São Paulo, Rua do Matão
São Paulo, Brazil
2 Universidade Federal do Rio de Janeiro, Observatório do Valongo, Ladeira do Pedro Antonio 43, 20080-090 Rio de Janeiro, RJ, Brazil
Received: 21 April 2009
Accepted: 21 September 2010
Barium stars are optimal sites for studying the correlations between the neutron-capture elements and other species that may be depleted or enhanced, because they act as neutron seeds or poisons during the operation of the s-process. These data are necessary to help constrain the modeling of the neutron-capture paths and explain the s-process abundance curve of the solar system. Chemical abundances for a large number of barium stars with different degrees of s-process excesses, masses, metallicities, and evolutionary states are a crucial step towards this goal. We present abundances of Mn, Cu, Zn, and various light and heavy elements for a sample of barium and normal giant stars, and present correlations between abundances contributed to different degrees by the weak-s, main-s, and r-processes of neutron capture, between Fe-peak elements and heavy elements. Data from the literature are also considered in order to better study the abundance pattern of peculiar stars. The stellar spectra were observed with FEROS/ESO. The stellar atmospheric parameters of the eight barium giant stars and six normal giants that we analyzed lie in the range 4300 < Teff/K < 5300, −0.7 < [Fe/H] ≤ 0.12 and 1.5 ≤ log g < 2.9. Carbon and nitrogen abundances were derived by spectral synthesis of the molecular bands of C2, CH, and CN. For all other elements we used the atomic lines to perform the spectral synthesis. A very large scatter was found mainly for the Mn abundances when data from the literature were considered. We found that [Zn/Fe] correlates well with the heavy element excesses, its abundance clearly increasing as the heavy element excesses increase, a trend not shown by the [Cu/Fe] and [Mn/Fe] ratios. Also, the ratios involving Mn, Cu, and Zn and heavy elements usually show an increasing trend toward higher metallicities. Our results suggest that a larger fraction of the Zn synthesis than of Cu is owed to massive stars, and that the contribution of the main-s process to the synthesis of both elements is small. We also conclude that Mn is mostly synthesized by SN Ia, and that a non-negligible fraction of the synthesis of Mn, Cu, and Zn is owed to the weak s-process.
Key words: stars: chemically peculiar / stars: abundances / techniques: spectroscopic / stars: AGB and post-AGB / stars: atmospheres
Based on spectroscopic observations collected at the European Southern Observatory (ESO), within the Observatório Nacional ON/ESO and ON/IAG agreements,under FAPESP project No. 1998/10138-8.
Full Tables 2 and 3 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (126.96.36.199) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/525/A63
© ESO, 2010
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