Spectral Variability of LBV star V532 (Romano's star)
  (abridged) We present the results of studying the spectral and photometric
variability of the luminous blue variable star V532 in M33. The photometric
variations are traced from 1960 to 2010, spectral variations - from 1992 to
2009. The star has revealed an absolute maximum of visual brightness
(1992-1994, high/cold state) and an absolute minimum (2007-2008, low/hot
state). The variability of the spectrum of V532 is fully consistent with the
temperature variations in its photosphere, while both permitted and forbidden
lines are formed in an extended stellar atmosphere. Broad components of the
brightest lines were found, the broadening of these components is due to
electron scattering in the wind parts closest to the photosphere. The wind
velocity clearly depends on the size of the stellar photosphere or on the
visual brightness, when brightness declines, the wind velocity increases. In
the absolute minimum a kinematic profile of the V532 atmosphere was detected.
The wind velocity increases and its temperature declines with distance from the
star. In the low/hot state, the spectral type of the star corresponds to
WN8.5h, in the high/cold state - to WN11. We studied the evolution of V532
along with the evolution of AG Car and the massive WR binary HD5980 in SMC.
During their visual minima, all the three stars perfectly fit with the WNL star
sequence by Crowther and Smith (1997). However, when visual brightness
increases, all the three stars form a separate sequence. It is possible that
this reflects a new property of LBV stars, namely, in the high/cold states they
do not pertain to the bona fide WNL stars.
