Chemical diversity of post-AGB stars in the LMC

We report on the chemical analysis based on UVES-VLT spectra of an exploratory sample of five post-AGB stars in the Large Magellanic Cloud. The sample reveals a wide chemical diversity, similar to the diversity seen in Galactic post-AGB stars. One object is a post-3rd dredge-up object, heavily enhanced in carbon and s-process elements; one object is carbon enhanced, but does not show s-process enhancements, and its chemistry is therefore not understood. The other three objects show some degree of depletion in their photosphere: the refractory elements are underabundant with respect to the non-refractories. This depletion pattern is understood as the result of a chemical process in which a gas-dust separation in the circumstellar environment is followed by a photospheric accretion of only the gas. In the Galaxy, the efficiency of this process is dependent on the initial metallicity. Here we show that at LMC metallicities, the depletion process can be very efficient. The most favourable circumstance for this process to occur is, if the circumstellar dust is trapped in a disk. The presence of a disk around those three stars is indeed revealed by IR measurements of Spitzer. The disk is likely related to binarity (see contributions of Gielen and Van Winckel in these proceedings).