Improved Laboratory Transition Probabilities for Ce II and Application to the Ce Abundances of the Sun and Five r-Process Rich, Metal-Poor Stars

Details Improved Laboratory Transition Probabilities for Ce II and Application to the Ce Abundances of the Sun and Five r-Process Rich, Metal-Poor Stars Improved Laboratory Transition Probabilities for Ce II and Application to the Ce Abundances of the Sun and Five r-Process Rich, Metal-Poor Stars

Jan 2009

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009aas...21340707l&link_type=abstract

American Astronomical Society, AAS Meeting #213, #407.07; Bulletin of the American Astronomical Society, Vol. 41, p.203

Astronomy and Astrophysics

Astronomy

Scientific paper

Cerium has the most complex spectra of the rare earths. This complexity results in many good lines for abundance measurements in the visible spectral region, but it also has hindered the calculation and/or measurement of accurate atomic transition probabilities. A new set of transition probabilities for 921 lines of Ce II is reported. These data are from a combination of recent radiative lifetime measurements using laser induced fluorescence with branching fractions from high resolution Fourier transform spectra. Our gf-values have been applied to refine the photospheric Ce abundance in the Sun and in 5 metal-poor giant stars with enhanced r-process abundances (those with [Fe/H] < -2, [Eu/Fe] > +0.5). For the Sun we derive log eps (Ce) = 1.61 ± 0.01 (sigma = 0.06 from 45 lines). This value is in excellent agreement with the meteoritic abundance: log eps (Ce) = 1.61 ± 0.02. The new Ce abundances for BD+17º3248, CS 22892-052, CS 31082-001, HD 115444, and HD 221170 are based on 26 to 40 lines in each star. All 5 mean abundance values have small standard deviations, 0.01dex, and sigma values ranging from 0.03 to 0.07. The resulting [Ce/Eu] are in quite good agreement with a Solar system r-process only value of [Ce/Eu] for a range of metallicity from [Fe/H] = -3.1 in CS 22892-052 to [Fe/H] = -2.1 in HD 221170. This agreement indicates that model results for the Solar system r-process fractions are accurate in spite of the fact that Ce is primarily from the s-process in Solar system material.
This work has been supported by the National Science Foundation through grants AST-0506324 to JEL and EDH, AST- 0607708 to CS, and AST-0707447 to JJC.

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