Context : GR 290 ( M 33/V532=Romano ’ s Star ) is a suspected post-LBV ( Luminous Blue Variable ) star located in M 33 galaxy that shows a rare Wolf–Rayet ( WR ) spectrum during its minimum light phase .
In spite of many studies , its atmospheric structure , its circumstellar environment and its place in the general context of massive stars evolution is poorly known . Aims : Detailed study of its wind and mass loss , and study of the circumstellar environment associated to the star . Methods : Long-slit spectra of GR 290 were obtained during its present minimum luminosity phase with the Gran Telescopio Canario covering the \sim 3600 - 7500 ÅÅ wavelength range together with contemporaneous BVRI photometry .
The data were compared with non-local thermodynamical equilibrium ( non-LTE ) model atmosphere synthetic spectra computed with CMFGEN and with CLOUDY models for ionized interstellar medium regions . Results : The current m _ { V } = 18.8 mag , is the faintest at which this source has ever been observed .
The non-LTE models indicate effective temperature T _ { eff } = 27000 - 30000 K at radius R _ { 2 / 3 } = 27 - 21 { R _ { \odot } } and mass loss rate \dot { M } =1.5 \times 10 ^ { -5 } { M _ { \odot } yr ^ { -1 } } .
The terminal wind speed { \mathrm { v } } _ { \infty } =620 { km~ { } s ^ { -1 } } is faster than ever before recorded while the current luminosity L _ { * } = ( 3.1 - 3.7 ) \times 10 ^ { 5 } { L _ { \odot } } is the lowest ever deduced .
It is overabundant in He and N and underabundant in C and O .
It is surrounded by an unresolved compact H II region with dimensions \leq 4 pc , from where H-Balmer , He i lines and [ { O \textsc { III } } ] and [ { N \textsc { II } } ] are detected .
In addition , we find emission from a more extended interstellar medium ( ISM ) region which appears to be asymmetric , with a larger extent to the East ( 16 - 40 pc ) than to the West . Conclusions : In the present long lasting visual minimum , GR 290 is in a lower bolometric luminosity state with higher mass loss rate .
The nearby nebular emission seems to suggest that the star has undergone significant mass loss over the past 10 ^ { 4 } -10 ^ { 5 } years and is nearing the end stages of its evolution .