*Review* **The History Goes On: Century Long Study of Romano's Star †**

**Olga Maryeva 1,2,\*, Roberto F. Viotti 3, Gloria Koenigsberger 4, Massimo Calabresi 5, Corinne Rossi 6 and Roberto Gualandi 7**


Received: 31 July 2019; Accepted: 13 September 2019; Published: 18 September 2019

**Abstract:** GR 290 (M 33 V0532 = Romano's Star) is a unique variable star in the M33 galaxy, which simultaneously displays variability typical for luminous blue variable (LBV) stars and physical parameters typical for nitrogen-rich Wolf-Rayet (WR) stars (WN). As of now, GR 290 is the first object which is confidently classified as a post-LBV star. In this paper, we outline the main results achieved from extensive photometric and spectroscopic observations of the star: the structure and chemical composition of its wind and its evolution over time, the systematic increase of the bolometric luminosity during the light maxima, the circumstellar environment. These results show that the current state of Romano's Star constitutes a fundamental link in the evolutionary path of very massive stars.

**Keywords:** galaxies: individual (M 33); stars: individual (GR 290, M 33 V0532); stars: variables: S Doradus; stars: Wolf-Rayet; stars: evolution; stars: winds, outflows
