Study of the IR-excess supergiant HD 331319

We report the discovery of brightness variability in the IR-excess early F supergiant HD 331319, a candidate post-AGBstar. Over three years of systematic UBV observations, the star showed low-amplitude (up to 0(.)(m) 17 in V) quasi-periodic brightness variations on a time scale of similar to 45 days. A preliminary analysis of our photometry indicates that HD 331319 and other typical post-AGBF supergiants have a similar pattern of variability. A study of the extinction toward HD 331319 leads us to conclude that the fraction of the circumstellar extinction is small for this star. We present low-resolution spectroscopy for HD 331319 and discuss the spectral classification of post-AGB F supergiants using HD 331319, HD 161796, HD 187885, and HD 56126 as examples.