Wind and nearby stellar environment of the quiescent luminous blue variable Var 2 in the Galaxy M33

Abstract: This paper is dedicated to the study of the luminous blue variable (LBV) Var 2 in the galaxy M33, which is currently in a "dormant" state and is observed as an Of/late-WN star. We had calculated self-consistent hydrodynamic non-LTE models of the extended atmosphere, taking into account the balance of radial forces in the wind of the star. This allowed us to obtain reliable estimates of the fundamental parameters of Var 2. The derived luminosity ($L=6.5\times10<sup>{5}\,L_\odot$), current mass ($M_* \approx23\,M_\odot$) and hydrogen abundance on the surface (${\rm X}<em>{\rm H}\approx43\%$) correspond well to a star with the initial mass $M</em>{\rm init}\approx50\,M_\odot$ and age $t_{\rm age}\approx5.0\times10<sup>6\,$years that is evolving from lower temperatures towards the Wolf-Rayet stars. A study of dynamic properties of the wind showed that the shape of the wind velocity profile of the Var 2 is close to the one of OB supergiants. In contrast, for the obtained mass loss rate $$\dot{M}=2.1\times10<sup>{-5}\,M_{\odot}\,\text{yr}<sup>{-1}$$, the ratio of the wind momentum to the luminosity of Var 2 is in good agreement with the values found for late-WN stars. At the same time, Var 2 has a lower terminal wind velocity $v_\infty\approx230\,$km$\,$s$<sup>{-1}$ compared to typical early-type supergiants or late-WN stars. Given the obtained age estimates, Var 2 could potentially have been ejected from the cluster associated with the nearest large star-forming region located at a distance of $\sim100\,$pc. However, statistical analysis of the projected distribution of stars in the vicinity of Var 2 suggests that this LBV could have formed in a local low-populated group.