Photometric variability and spectral features of the protoplanetary nebula LSII+34°26=V1853 Cyg

We present photoelectric and spectroscopic observations of the protoplanetary object V 1853 Cyg, a B supergiant with an IR excess. Over two years of its observations, the star exhibited rapid irregular light variations with amplitudes DeltaV = 0.(m)3, DeltaB = 0.(m)3, DeltaU = 0.(m)4 and no correlation between color and magnitude. Its mean magnitude has not changed since the first UBV observations in 1973 (Drilling 1975). Low-resolution spectroscopic observations show that the spectrum of V 1853 Cyg in 2000 corresponded to that of a B1 - B2 star with T-eff similar to 20000 K. High-resolution spectroscopic observations confirm the conclusion that the profiles of absorption and emission lines are variable. We identified the star's spectral lines and measured the equivalent widths of more than 40 lines. The star's radial velocity is <V-r> = -49 +/- 5 km s(-1), as measured from absorption lines, and ranges from -50 to -85 km s(-1) for different lines, as measured from shell emission lines. The velocity of the dust clouds on the line of sight determined from diffuse interstellar bands (DIBs) and from interstellar Na I lines is <V-r> = -16 +/- 5 km s(-1). The P Cyg profiles of the He I lambda 5876 Angstrom and lambda 6678 Angstrom lines suggest an ongoing mass loss by the star. An analysis of the observational data confirms the conclusion that the star belongs to the class of intermediate-mass protoplanetary objects. (C) 2001 MAIK "Nauka/Interperiodica".