Spectral Variability of Romano's Star

TL;DR

This study analyzes 15 years of spectral and photometric data of Romano's star, revealing its spectral variability and physical parameters, and comparing its behavior to other luminous blue variables.

Contribution

It provides the most comprehensive spectral analysis of Romano's star, identifying about 100 spectral lines and characterizing its wind velocity and nebular parameters.

Findings

Romano's star behaves as an emission line supergiant at maximum brightness.

In minimum, it resembles late WN stars and is hotter than similar LBVs.

Wind velocity is approximately 360 km/s.

Abstract

We combine archival spectral observations of the LBV star V532 (Romano's star) together with the 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 in the minima. We identify about 100 spectral lines in the 3700..7300 Angstrom wavelength range. For today, our spectroscopy is the most comprehensive for this object. The velocity of the wind is derived using HeI triplet lines (360+/-30 km/s). Physical parameters of the nebula around V532 are estimated.