Improved log(gf) Values for Lines of Ti II and New Titanium Abundances in the Sun and the Metal-Poor Star HD 84937

Wood, Michale (1), Lawler J. E. (1), Sneden C. (2) and Cowan J. J. (3) ((1) University of Wisconsin; (2) University of Texas; (3) University of Oklahoma)

New atomic transition probability measurements for 364 lines of Ti II in the UV through near IR are reported. These results are used to determine the Ti abundance of the Sun and a very metal-poor main-sequence turnoff dwarf star over a range of wavelength and E. P. values to search for non-LTE effects. Branching fractions from data recorded using a Fourier transform spectrometer (FTS) and a 3 m echelle spectrometer are combined with published radiative lifetimes from laser induced fluorescence measurements to determine these new transition probabilities. The new results are in generally good agreement with previously reported FTS measurements and the NIST Atomic Spectra Database. The use of a new echelle spectrometer, new radiometric calibration methods, and independent data analysis routines allows for a reduction of systematic errors and overall improvement in transition probability uncertainties over previous measurements. This work represents the largest and most complete single source of Ti II transition probabilities to date in this wavelength range. The new Ti II data are applied to high resolution visible and UV spectra of the Sun and HD 84937 to derive new, more accurate titanium abundances. We use 36 lines from the solar photosphere to derive log(ε(Ti))=4.98 (σ=0.03), in good agreement with the recommended Ti abundance from previous solar abundance reviews and in very good agreement with our solar abundance derived using Ti I. For HD 84937, a preliminary analysis with a subset of available Ti II lines yields log(ε(Ti))=3.12 (σ=0.04, 19 lines), or [Ti/H]=-1.86, also in very good agreement with our abundance derived using Ti I. This work is supported by NASA grant NNX10AN93G and NSF grant AST-1211055 (JEL) and NSF grants AST-0908978 and AST-1211585 (CS).

See complete preprint –>…22134804W

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