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| Main Authors: | , , , , |
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| Format: | Preprint |
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2025
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| Online Access: | https://arxiv.org/abs/2510.11802 |
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| _version_ | 1866908910017839104 |
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| author | Kostenkov, A. Solovyeva, Y. Dedov, E. Vinokurov, A. Sarkisyan, A. |
| author_facet | Kostenkov, A. Solovyeva, Y. Dedov, E. Vinokurov, A. Sarkisyan, A. |
| contents | Luminous Blue Variables (LBVs) are massive stars with extreme luminosities, exhibiting significant irregular photometric and spectroscopic variability. This paper is dedicated to the study of dormant LBV Var$\,$2 in the galaxy M33, which has not shown significant brightness changes for almost century and currently observed as Ofpe/WN9 star. In order to obtain reliable estimates of the fundamental parameters of Var$\,$2, we had calculated self-consistent hydrodynamic models of the extended atmosphere, assuming non-local thermodynamic equilibrium (non-LTE) and taking into account the balance of radial forces in the wind of the star. Spectral modeling yields luminosity $L=6.5\times10^{5}\,L_\odot$, current mass $M_* \approx23\,M_\odot$ and hydrogen abundance on the surface ${\rm X}_{\rm H}\approx43\%$. Comparison with evolutionary tracks indicates that these parameters correspond to a star with the initial mass $M_{\rm init}\approx50\,M_\odot$ and age $t_{\rm age}\approx4.4\,$Myr 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 Var$\,$2 is close to the one of O- and early B-supergiants rather than Wolf-Rayet stars. In contrast, for the obtained mass-loss rate $\dot{M}=2.1\times10^{-5}\,M_{\odot}\,\text{yr}^{-1}$, the ratio of the wind momentum to the luminosity of Var$\,$2 is in good agreement with the values found for WNL stars. Given the obtained age estimates, Var$\,$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$\,$2 suggests that this LBV could have formed in a local low-populated group. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2510_11802 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Probing the wind and evolutionary state of the quiescent luminous blue variable Var$\,$2 in the Galaxy M33: constraints from self-consistent non-LTE modeling Kostenkov, A. Solovyeva, Y. Dedov, E. Vinokurov, A. Sarkisyan, A. Solar and Stellar Astrophysics Luminous Blue Variables (LBVs) are massive stars with extreme luminosities, exhibiting significant irregular photometric and spectroscopic variability. This paper is dedicated to the study of dormant LBV Var$\,$2 in the galaxy M33, which has not shown significant brightness changes for almost century and currently observed as Ofpe/WN9 star. In order to obtain reliable estimates of the fundamental parameters of Var$\,$2, we had calculated self-consistent hydrodynamic models of the extended atmosphere, assuming non-local thermodynamic equilibrium (non-LTE) and taking into account the balance of radial forces in the wind of the star. Spectral modeling yields luminosity $L=6.5\times10^{5}\,L_\odot$, current mass $M_* \approx23\,M_\odot$ and hydrogen abundance on the surface ${\rm X}_{\rm H}\approx43\%$. Comparison with evolutionary tracks indicates that these parameters correspond to a star with the initial mass $M_{\rm init}\approx50\,M_\odot$ and age $t_{\rm age}\approx4.4\,$Myr 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 Var$\,$2 is close to the one of O- and early B-supergiants rather than Wolf-Rayet stars. In contrast, for the obtained mass-loss rate $\dot{M}=2.1\times10^{-5}\,M_{\odot}\,\text{yr}^{-1}$, the ratio of the wind momentum to the luminosity of Var$\,$2 is in good agreement with the values found for WNL stars. Given the obtained age estimates, Var$\,$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$\,$2 suggests that this LBV could have formed in a local low-populated group. |
| title | Probing the wind and evolutionary state of the quiescent luminous blue variable Var$\,$2 in the Galaxy M33: constraints from self-consistent non-LTE modeling |
| topic | Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2510.11802 |