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G.R. Stanley, Jr., W.D. Cochran, C. Sneden (U.Texas-Austin Astronomy Dept. \& McDonald Observatory)
Can we predict which stars formed planets? We test the hypothesis that those stars with planets have lower overall Li abundances than their counterparts with no detectable planetary systems. If this is true, then massive circumstellar disks which formed `giant' planets may have helped torsionally brake the parent stars during the pre-main-sequence phase of their evolution. This rotational braking might help these stars destroy lithium nuclei more easily as increased mixing, due to the decrease in angular momentum, would circulate the Li into warmer regions where it is destroyed.
We test whether the measured stellar lithium abundance reflects the predicted amount of lithium destruction as a function of mass and age. As part of this study, we examined the case of 16 Cyg, a binary system where the photospheric abundances are essentially the same except that 16 Cyg A has at least five times more lithium than 16 Cyg B while only the latter has a detected planet. We analyzed spectra of stars provided by Marcy & Butler to investigate whether any trends of Li, evolutionary state, or metallicity could be found that correlate with the presence of planets.
Using high resolution (R ~ 70000), high signal to noise (~ 200) spectra of 58 F-K dwarf field stars we determined self-consistent photospheric Fe and Li abundances which substantially agree with published results. Comparing our measured abundances to theoretical ZAMS abundances we deduced the Li depletion for similarly massive stars as a function of age. Stars with a giant planet found to be unexplained outliers include the Sun and 51 Peg. These stars in particular show enhanced Li depletion relative to other stars of similar mass and age.