2023MNRAS.518.4345S

We continue the search for luminous blue variables (LBVs) in Local Volume galaxies in order to study their fundamental parameters. In this paper, we report the discovery of two new LBVs in the dwarf irregular galaxy NGC 1156. Both stars exhibit spectral variability simultaneously with strong brightness variations: ΔR_c = 0.84 ± 0.23^m for J025941.21+251412.2 and ΔR_c = 2.59 ± 0.10^m for J025941.54+251421.8. The bolometric luminosities of the stars are in the range of L_Bol ≈ (0.8-1.6) × 10⁶ L_⊙. These values are corrected for reddening A_V ≈ 0.9 and are given for the distance to the galaxy D = 7.0 ± 0.4 Mpc, which we have measured by the tip of the red-giant branch method. Both stars are above the Humphreys-Davidson limit in the region of relatively low temperatures, T_eff ≲ 10 kK, on the temperature-luminosity diagram. J025941.54+251421.8 had a temperature below the hydrogen ionization threshold at maximum brightness, exhibiting behaviour very similar to that of the known LBV R71 during its 2012 outburst. We have estimated the masses of the detected LBVs and studied the properties of their stellar environment. We discuss our results within the framework of both a single star and a binary system evolution scenario for LBVs.