Nissen, P. E.P. E.NissenChristensen-Dalsgaard, J.J.Christensen-DalsgaardMosumgaard, J. R.J. R.MosumgaardSilva Aguirre, V.V.Silva AguirreSPITONI, EmanueleEmanueleSPITONIVerma, K.K.Verma2025-03-112025-03-1120200004-6361http://hdl.handle.net/20.500.12386/36633Aims: Previous high-precision studies of abundances of elements in solar twin stars are extended to a wider metallicity range to see how the trends of element ratios with stellar age depend on [Fe/H]. <BR /> Methods: HARPS spectra with signal-to-noise ratios S/N ≳ 600 at λ ∼ 6000 Å were analysed with MARCS model atmospheres to obtain 1D LTE abundances of C, O, Na, Mg, Al, Si, Ca, Ti, Cr, Fe, Ni, Sr, and Y for 72 nearby solar-type stars with metallicities in the range of -0.3 ≲ [Fe/H] ≲ +0.3 and ASTEC stellar models were used to determine stellar ages from effective temperatures, luminosities obtained via Gaia DR2 parallaxes, and heavy element abundances. <BR /> Results: The age-metallicity distribution appears to consist of the following two distinct populations: a sequence of old stars with a steep rise of [Fe/H] to ∼ + 0.3 dex at an age of ∼7 Gyr and a younger sequence with [Fe/H] increasing from about -0.3 dex to ∼ + 0.2 dex over the last 6 Gyr. Furthermore, the trends of several abundance ratios, [O/Fe], [Na/Fe], [Ca/Fe], and [Ni/Fe], as a function of stellar age, split into two corresponding sequences. The [Y/Mg]-age relation, on the other hand, shows no offset between the two age sequences and has no significant dependence on [Fe/H], but the components of a visual binary star, ζ Reticuli, have a large and puzzling deviation. <BR /> Conclusions: The split of the age-metallicity distribution into two sequences may be interpreted as evidence of two episodes of accretion of gas onto the Galactic disk with a quenching of star formation in between. Some of the [X/Fe]-age relations support this scenario but other relations are not so easy to explain, which calls for a deeper study of systematic errors in the derived abundances as a function of [Fe/H], in particular 3D non-LTE effects. <P />Full Tables 1 and 2 are only available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr/">http://cdsarc.u-strasbg.fr</A> (ftp://130.79.128.5) or via <A href="http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/640/A81">http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/640/A81</A>STAMPAenArticle10.1051/0004-6361/2020383002-s2.0-85090121651https://www.aanda.org/articles/aa/full_html/2020/08/aa38300-20/aa38300-20.htmlhttp://arxiv.org/abs/2006.06013v12020A&A...640A..81NFIS/05 - ASTRONOMIA E ASTROFISICA