Light Variations in the Candidate for Protoplanetary Objects HD 179821 = V1427 Aql in 1899-1999

We present photoelectric and photographic observations of the supergiant HD 179821 with a large infrared excess, a candidate for protoplanetary objects. Over, ten years of our UBV observations, the star exhibited semiregular light variations with amplitudes Delta V = 0.10 mag, B = 0.15 mag, and U = 0.25 mag, as well as systematic color and light variations. From 1990 until 1996, the yearly mean U-B and B-V color indices decreased by 0.25 and 0.15, respectively. After 1996, the motion of the star in the two-color (B-V)-(U-B) diagram upward and to the left slowed down. The color excess that we derived from our observations, by assuming that the star's spectral type was F3I in the 1990s, is E(B-V) = 1.0. The photographic observations of HD 179821 from 1899 until 1989 show that its brightness m_pg generally increased while significantly fluctuating. An analysis of the observational data suggests that HD 179821 is most likely a post-AGB star of intermediate or low mass.