Spectral Variability of Romano's Star

Abstract

We combine archival spectral observations of the LBV star V532 (Romano’s star) together with existing photometric data in the B band. Spectroscopic data cover 15 years of observations (from 1992 to 2007). We show that the object in maximum of brightness behaves as an emission line supergiant while in minimum V532 moves along the sequence of late WN stars. In this sense, the object behaves similarly to the well-known Luminous Blue Variable (LBV) stars AG Car and R127, but is somewhat hotter at the minima. We identify about 100 spectral lines in the 3700 - 7300 °A wavelength range. As of today, our spectroscopy is the most comprehensive for this object. The velocity of the wind is derived using the He I triplet lines (360±30 km s-1). Physical parameters of the nebula around V532 are estimated.