An unusual carbon-rich RV Tauri star in the Large Magellanic Cloud

We-present the first spectra of an RV Tauri star in the Large Magellanic Cloud. MACHO* 04:55:43.2-67:51:10 is a recently identified RV Tauri variable with a double period of 112.448 days. Three low-resolution (210 Angstrom mm(-1), or 7 Angstrom resolution) spectrograms obtained of this star show strong C-2 bands with a pronounced phase dependence, their strength being greatest at minimum light. The overall spectrum of MACHO*04:55:43.2-67:51:10 is similar to those observed in proto-planetary nebulae. This unusual star therefore combines the main spectral anomaly of the proto-planetary nebulae with RV Tauri-like photometric variability. The occurrence of a luminous, carbon-rich RV Tauri-like star may be explained by assuming that it is a star of 1-2 solar masses that has evolved through the M-S-C transition on the extended asymptotic giant branch (AGB) and is now moving to the blue in the pre-planetary nebula stage. This star may therefore represent a link between these two types of star and strengthen the post-AGE interpretation of RV Tauri stars.