First detection of photospheric depletion in the Large Magellanic Cloud

Context. Recent photospheric abundance studies of galactic field RV Tauri stars show that depletion of refractory elements is rather common in these evolved objects. Aims. The process that creates this chemical anomaly is not understood well, but it probably requires the presence of gravitationally bound dust in a binary system. We test for the presence of depletion in extra-galactic objects. Methods. A detailed photospheric abundance study on the basis of high-quality UVES spectra was performed on the RV Tauri star in the LMC: MACHO82.8405.15. Abundances were derived using a critically compiled line list with accurate log(gf) values and the latest Kurucz model atmospheres. Results. With [Fe/H] = -2.6 in combination with [Zn/Fe]= +2.3 and [S/Ti]= +2.5, MACHO82.8405.15 displays a strong depletion abundance pattern. The effect of the depletion is comparable to the strongest depletions seen in field Galactic RV Tauri stars. Conclusions. The chemical analysis of MACHO 82.8405.15 proves that the depletion process also occurs in the extragalactic members of the RV Tauri pulsation class. Our program star is a member of a larger sample of LMC RV Tauri objects. This sample is unique, since the distances of the members are well-constrained. Further studies of this sample are therefore expected to gain deeper insight into the poorly understood depletion phenomenon and of the evolutionary status of RV Tauri stars in general.