Spectral lines as probes of surface gravities and galactic nucleosynthesis

Four spectroscopic analyses based on observations of spectral lines in the atmospheres of late type stars are presented. Surface gravities for eight G8IV-K2III stars, as well as for α Bootis (Arcturus) and α Centauri A and B (Rigil Kentaurus) were determined from the pressure sensitive wings of a number of strong metal lines. The pressure sensitivity of these line wings were determined from the appearance of the lines in the solar spectrum. The resulting surface gravities have been compared to surface gravities determined by other methods and were shown to agree well and to be very insensitive to uncertainties in the model atmospheres adopted in the analyses. Chemical abundances of twelve elements from Na to Ni and tentative abundances of five heavier elements were also obtained. The first results of an abundance determination primarily of light elements in a number of F and G dwarfs of different ages are reported. The final results will be used for investigating details of the history of element synthesis in the Galactic disk. Evidence is found for metallicity inhomogeneities in the interstellar medium, or gradients in the metallicity as a function of galactocentric distance, at agiven time. The results also confirm the relative overabundances previously found for oxygen in metal poor stars and similar results are found for the α-elements. Accurate life-time measurements are reported for excited levels in singly ionized samarium. Oscillator strengths for Sm II lines have been determined using these lifetimes and used for a determination of the solar samarium abundance by spectrum synthesis. The recommended value is consistent with that found from meteorites. One new candidate line for the investigation of partial solar and stellar samarium isotopic ratios is suggested. (author)