HD172481: A super lithium-rick metal-deficient post-AGB binary with a red AGB companion

We present in this paper a study on the peculiar supergiant HD 172481. Its spectral type (F2Ia), high galactic latitude (b = -10 degrees .37), circums tellar dust, high radial velocity and moderate metal deficiency ([Fe/H] = - 0.55) confirm the post-AGE character of this object. A detailed chemical an alysis shows slight but real s-process overabundances, however no CNO-enhan cement was detected. Furthermore, the spectral energy distribution and the TiO bands in the red part of the spectrum reveal a red luminous companion. The luminosity ratio of the hot F type component and this cool M type compa nion L-F/L-M is derived for a reddening of E(B - V) = 0.44 (L-F/L-M similar to 1.8) and indicates that the companion must also be strongly evolved and probably evolving along the AGE. Neither our photometric data-set, nor our radial velocity monitoring show evidence for orbital variability which may indicate that the period is too large for direct binary interaction. Most interestingly, a strong lithium resonance line is detected, which yields an abundance of log epsilon (Li) = 3.6. Several explanations for this large l ithium content are explored.