|
Description
We present new photometric data and analyze long-term UBV observations of three candidates for protoplanetary nebulae - F supergiants with infrared excesses at high Galactic latitudes -IRAS 18095+2704, IRAS 19386+0155, and IRAS 19500-1709. All these stars exhibit quasi-periodic low-amplitude variations caused by pulsations against the background of long-term brightness trends. For IRAS 18095+2704 = V887 Her, we have found a pulsation period of 109 days and revealed a linear brightness trend - the star brightens at constant (within the limits of the measurement errors) yearly mean color indices. The light curve of IRAS 19386+0155 = V1648 Aql in 2000-008 is represented by a wave with a fundamental period of 102 days whose modulation with a close period of 98 days leads to variations with a variable amplitude. V1648 Aql also shows a systematic rise in V brightness along with a reddening. IRAS 19500-1709 = V5112 Sgr exhibits irregular pulsations with periods of 39 and 47 days. The long-term variability component of V5112 Sgr may indicate that the star is binary.
|
