Long-Term Monitoring of the Variable Star J022237.31+422234.2 in NGC 891: a New LBV or a Yellow Hypergiant?

We continue to search for luminous blue variables (LBVs) in the Local Volume galaxies to further study their fundamental parameters in relation to the age of their stellar environments and the metallicity of the gas in their host galaxies. In this paper, we report the discovery of the luminous star J022237.31+422234.2 ( $$M_{V{\textrm{max}}}<{-}10\overset{\textrm{m}}{.}2$$ ) in the galaxy NGC 891 located at a distance of about 10 Mpc. The study involves data from ground-based and space telescopes (HST, JWST). Over the period from 1997 to 2024, the star exhibited the photometric variability $$\Delta V=1\overset{\textrm{m}}{.}12\pm 0\overset{\textrm{m}}{.}06$$ . A statistical analysis of the broadband photometric data revealed a direct correlation between the $$(V-I_{c})$$ color index and the $$V$$ -band brightness of the star, while no significant variability was observed in $$(B-V)$$ and $$(V-R_{c})$$ . Based on a comparison of the optical spectrum obtained with the 6-m BTA telescope with a grid of extended atmosphere models, we estimated the photospheric temperature ( $$8000\lesssim T_{\textrm{eff}}\lesssim 10100\text{ K}$$ ) and the mass-loss rate ( $$8\times 10^{-5}\lesssim\dot{M}\lesssim 5\times 10^{-4}M_{\odot}\text{ yr}^{-1}$$ ). Fitting the observed optical spectral energy distribution with models of extended atmospheres, accounting for interstellar extinction, yielded a bolometric luminosity estimate of $$1.1\times 10^{6}L_{\odot}\lesssim L\lesssim 2.6\times 10^{6}L_{\odot}$$ . In the infrared range, a significant excess emission was detected at 1.5–8 $$\mu$$ m, which may indicate the presence of a warm dust with a temperature of 1300 K. The observed properties of J022237.31+422234.2 suggest its classification as a yellow hypergiant or an LBV in a cold state.