2020MNRAS.498.5093M

We present the results of study of the Galactic candidate luminous blue variable Wray 15-906, revealed via detection of its infrared circumstellar shell (of ≃2 pc in diameter) with the Wide-field Infrared Survey Explorer and the Herschel Space Observatory. Using the stellar atmosphere code CMFGEN and the Gaia parallax, we found that Wray 15-906 is a relatively low-luminosity, log(L/ L_☉)~5.4, star of temperature of 25 ± 2 kK, with a mass-loss rate of ~3×10^–5 M_☉_ yr_^–1, a wind velocity of 280±50 km s^–1, and a surface helium abundance of 65 ± 2 per cent (by mass). In the framework of single-star evolution, the obtained results suggest that Wray 15-906 is a post-red supergiant star with initial mass of ~25 M_☉and that before exploding as a supernova it could transform for a short time into a WN11h star. Our spectroscopic monitoring with the Southern African Large Telescope does not reveal significant changes in the spectrum of Wray 15-906 during the last 8 yr, while the V-band light curve of this star over years 1999-2019 shows quasi-periodic variability with a period of ≃1700 d and an amplitude of ≃0.2 mag. We estimated the mass of the shell to be 2.9±0.5 M_☉assuming the gas-to-dust mass ratio of 200. The presence of such a shell indicates that Wray 15-906 has suffered substantial mass-loss in the recent past. We found that the open star cluster C1128-631 could be the birth place of Wray 15-906 provided that this star is a rejuvenated product of binary evolution (a blue straggler).