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arXiv · 1711.03643

The temporal evolution of neutron-capture elements in the Galactic discs

Lorenzo Spina·Jorge Meléndez·Amanda I. Karakas·Leonardo dos Santos·Megan Bedell·Martin Asplund·Ivan Ramírez·David Yong·Alan Alves-Brito·Jacob L. Bean·Stefan Dreizler
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Abstract

Important insights into the formation and evolution of the Galactic disc(s) are contained in the chemical compositions of stars. We analysed high-resolution and high signal to noise HARPS spectra of 79 solar twin stars in order to obtain precise determinations of their atmospheric parameters, ages ($σ$$\sim$0.4 Gyr) and chemical abundances ($σ$$<$0.01~dex) of 12 neutron-capture elements (Sr, Y, Zr, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, and Dy). This valuable dataset allows us to study the [X/Fe]-age relations over a time interval of $\sim$10 Gyr and among stars belonging to the thin and thick discs. These relations show that i) the $s$-process has been the main channel of nucleosynthesis of $n$-capture elements during the evolution of the thin disc; ii) the thick disc is rich in $r$-process elements which suggests that its formation has been rapid and intensive. %; iii) a chemical continuity between the thin and thick discs is evident in the abundances of Ba. In addition, the heavy (Ba, La, Ce) and light (Sr, Y, Zr) $s$-process elements revealed details on the dependence between the yields of AGB stars and the stellar mass or metallicity. Finally, we confirmed that both [Y/Mg] and [Y/Al] ratios can be employed as stellar clocks, allowing ages of solar twin stars to be estimated with an average precision of $\sim$0.5~Gyr.

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Lorenzo Spina, Jorge Meléndez, Amanda I. Karakas, Leonardo dos Santos, Megan Bedell, Martin Asplund, Ivan Ramírez, David Yong, Alan Alves-Brito, Jacob L. Bean, Stefan Dreizler. 2017-11-09. The temporal evolution of neutron-capture elements in the Galactic discs. https://doi.org/10.1093/mnras%2Fstx2938

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