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Discovery of new LBVs in the Local Volume galaxy NGC 1156

Russian version

    Luminous Blue Variables (LBVs) are a rare type of massive stars with high luminosity and strong photometric and spectral variability. Clarification of the nature and evolutionary status of LBVs requires a significant expansion of the sample of the known and studied stars of this type. In the galaxy NGC 1156, we discovered two massive stars with the emission spectra which, according to the results of spectroscopy and photometric monitoring at the 6-m SAO RAS telescope (BTA) and the 2.5-m telescope of the Caucasian Mountain Observatory of SAI MSU are classified as LBVs. During the observation program at the BTA aimed at searching for LBVs in the Local Volume, our research team discovered and confirmed the status of 5 LBVs, while in total about 20 stars of this type are known at such distances. Modeling of the spectral energy distributions and spectra of two detected LBVs made it possible to determine their bolometric luminosities (8×105 and 1.6×106 of solar luminosities with the 10% accuracy), the photosphere temperatures (<7000 K for the fainter and 7900±400 K for the brighter star). Both stars have extremely large radii for LBVs, 650-680 of solar radii.
Fig.1. Observed spectrum of the brighter LBV in NGC 1156 (the red line) compared with the best fit CMFGEN model (the blue line). The Fe II lines are marked with the black vertical lines.

Y. Solovyeva, A. Kostenkov, E. Dedov, A. Vinokurov. “Wind parameters of the new LBV in NGC 1156”, Proceedings of Science, accepted, 2022;
2. Y. Solovyeva, A. Vinokurov, N. Tikhonov, A. Kostenkov, K. Atapin, A. Sarkisyan, A. Moiseev, S. Fabrika, D. Oparin, A. Valeev. “Search for LBVs in the Local Volume galaxies: study of two stars in NGC 1156”, Monthly Notices of the Royal Astronomical Society, accepted, 2022.

Contact person - Solovyeva Y.N., Ph.D. in Physics and Mathematics, Junior Researcher in the Laboratory of Stellar Physics
The research is supported by the grant of the Ministry of Science and Higher Education of the Russian Federation No. 075-15-2022-262 (13.MNPMU.21.0003)