Abundances in Metal-rich Stars ?

We have derived elemental abundances of O, Ni as well as for a number of s-elements for 47 G and K dwarf, with Me/H]> 0:1 dex. The selection of stars was based on their kinematics as well as on their uvby ?-photometry. One sample of stars on rather eccentric orbits traces the chemical evolution interior to the solar orbit and another, on circular orbits, the evolution around the solar orbit. A few Extreme Population I stars were included in the latter sample. The stars have ?0:1 dex < Fe=H] < 0:42 dex. The spectroscopic Fe/H] correlate well with the Me/H] derived from uvby ? photometry. We nd that the elemental abundances of Mg, Al, Si, Ca, Ti, Cr and Ni all follow Fe/H]. Our data put further constraints on models of galactic chemical evolution, in particular of Cr, Mn and Co which has not previously been studied for dwarf stars with Me=H] > 0:1 dex. The increase in Na/Fe] and Al/Fe] as a function of Fe/H] found previously by Edvardsson et al. (1993a) has been connrmed for Na/Fe]. This upturning relation, and the scatter around it, are shown not to be due to a mixture of populations with diierent mean distances to the galactic centre. We do not connrm the same trend for aluminium, which is somewhat surprising since both these elements are thought to be produced in the same environments in the pre-supernova stars. Nor have we been able to trace any tendency for relative abundances of O, Si, and Ti relative to Fe to vary with the stellar velocities , i.e. the stars present mean distance to the galactic centre. These results imply that there is no signiicant difference in the chemical evolution of the diierent stellar populations for stars with Me/H]> 0:1 dex. We nd that O/Fe] continue to decline with increasing Fe/H] and that oxygen and europium correlate well. However Si/Fe] and Ca/Fe] seem to stay constant. A real ("cosmic") scatter in Ti/Fe] at given Fe/H] is suggested as well as a decreasing abundance of the s-elements relative to iron for the Send ooprint requests to: S. Feltzing [email protected] ? Based on observations at the McDonald Observatory. most metal-rich dwarf stars. We discuss our results in the context of recent models of galactic chemical evolution. In our sample we have included a few very metal rich stars, sometimes called SMR (super metal rich) stars. We nd …