Variability of Hot Supergiant IRAS 19336-0400 in the Early Phase of Planetary Nebula Ionization

We present photoelectric and spectral observations of a hot candidate proto-planetary nebula-early B-type supergiant with emission lines in spectrum-IRAS 19336-0400. The light and color curves display fast irregular brightness variations with maximum amplitudes Delta V = 0.(m)30, Delta B = 0.(m)35, Delta U = 0.(m)40 and color-brightness correlations. By the variability characteristics IRAS 19336-0400 appears similar to other hot proto-planetary nebulae. Based on low-resolution spectra in the range lambda 4000-7500 angstrom we have derived absolute intensities of the emission lines H alpha, H beta, H gamma, [S II], [N II], physical conditions in gaseous nebula: n(e) = 10(4) cm(-3), T-e = 7000 +/- 1000 K. The emission line H alpha, H beta equivalent widths are found to be considerably variable and related to light changes. By UBV-photometry and spectroscopy the color excess has been estimated: EB-V = 0.50-0.54. Joint photometric and spectral data analysis allows us to assume that the star variability is caused by stellar wind variations.