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Stellar photospheres of post-asymptotic giant branch stars bear witness tothe internal chemical enrichment processes, integrated over their entirestellar evolution. Here we study post-AGB stars in the Large Magellanic Cloud(LMC). With their known distances, these rare objects are ideal tracers of AGBnucleosynthesis and dredge-up phenomena.  We used the UVES spectrograph mounted on the Very Large Telescope (VLT) atthe European Southern Observatory (ESO), to obtain high-resolution spectra withhigh signal-to-noise (S/N) of a sample of four post-AGB stars. The objectsdisplay a spectral energy distribution (SED) that indicates the presence ofcircumstellar dust.  All objects are carbon-rich, and strongly enhanced in s-process elements. Wededuced abundances of heavy s-process elements for all stars in the sample, andeven found an indication of the presence of Hg in the spectrum of one object.The metallicity of all stars except J053253.51-695915.1 is considerably lowerthan the average value that is observed for the LMC. The derived luminositiesshow that we witness the late evolution of low-mass stars with initial massesclose to 1 solar mass. An exception is J053253.51-695915.1 and we argue thatthis object is likely a binary.  We confirmed the correlation between the efficiency of the third-dredge upand the neutron exposure that is detected in Galactic post-AGB stars. Thenon-existence of a correlation between metallicity and neutron irradiation isalso confirmed and expanded to smaller metallicities. We confirm the status of21-micron stars as post-Carbon stars. Current theoretical AGB modelsoverestimate the observed C/O ratios and fail to reproduce the variety ofs-process abundance patterns that is observed in otherwise very similarobjects. Similar results have recently been found for a post-AGB star in theSmall Magellanic Cloud (SMC).

Detailed abundance study of four s-process enriched post-AGB stars in the Large Magellanic Cloud