IMPROVED Cr II log(gf) VALUES AND ABUNDANCE DETERMINATIONS IN THE PHOTOSPHERES OF THE SUN AND METAL-POOR STAR HD 84937


Lawler J. E. , SNEDEN C., NAVE G., DEN HARTOG E. A. , Emrahoglu N. , COWAN J. J.

ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, cilt.228, 2017 (SCI İndekslerine Giren Dergi) identifier identifier identifier

  • Cilt numarası: 228 Konu: 1
  • Basım Tarihi: 2017
  • Doi Numarası: 10.3847/1538-4365/228/1/10
  • Dergi Adı: ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES

Özet

New emission branching fraction (BF) measurements for 183 lines of the second spectrum of chromium (Cr II) and new radiative lifetime measurements from laser-induced fluorescence for 8 levels of Cr+ are reported. The goals of this study are to improve transition probability measurements in Cr II and reconcile solar and stellar Cr abundance values based on Cr I and Cr II lines. Eighteen spectra from three Fourier Transform Spectrometers supplemented with ultraviolet spectra from a high-resolution echelle spectrometer are used in the BF measurements. Radiative lifetimes from this study and earlier publications are used to convert the BFs into absolute transition probabilities. These new laboratory data are applied to determine the Cr abundance log e in the Sun and metal-poor star HD 84937. The mean result in the Sun is < log epsilon(Cr II) > - 5.624 +/- 0.009 compared to < log e(Cr I) > - 5.644 +/- 0.006 on a scale with the hydrogen abundance log epsilon(H) = 12 and with the uncertainty representing only line-to-line scatter. A Saha (ionization balance) test on the photosphere of HD 84937 is also performed, yielding < log epsilon(Cr II) > = 3.417 +/- 0.006 and < log epsilon(Cr I, lower level excitation potential E. P. > 0 eV)> = 3.374 +/- 0.011 for this dwarf star. We find a correlation of Cr with the iron-peak element Ti, suggesting an associated nucleosynthetic production. Four iron-peak elements (Cr along with Ti, V, and Sc) appear to have a similar (or correlated) production history-other iron-peak elements appear not to be associated with Cr.