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Scientific achievements, Galaxy sector

Direct evidence of the fossil origin of large-scale magnetic fields of chemically peculiar stars obtained
A spectropolarimetric survey of all chemically peculiar (CP) stars identified in the Orion OB1 association of young stars has been performed with the 6-m BTA telescope. The sample includes 56 CP stars aged 1-15 Myr having a common origin within the association. 31 stars have magnetic fields stronger than 500 G including 14 stars, whose fields have been found for the first time in our survey. The analysis of the obtained data shows a decrease in the fraction of CP stars in general and in the fraction of magnetic CP stars in particular with age, relative to normal stars of the same type but without significant chemical anomalies. It was found for the first time that no magnetic field is detected in objects younger than 1 Myr; later the structure of the star is rearranged and the magnetic field becomes visible reaching a maximum at times of the order of 2-3 Myr and then drops by a factor of 3 at times of the order of 10 Myr. The result obtained is a direct and statistically reliable confirmation of the fossil origin of the magnetic fields of stars of early spectral types.
Authors: Semenko E.A. (National Astronomical Research Institute of Thailand), Romanyuk I.I., Yakunin I.A., Kudryavtsev D.O., Moiseeva A.V. (SAO RAS)
Published:
Semenko E., Romanyuk I., Yakunin I., Kudryavtsev D., Moiseeva A. Spectropolarimetry of magnetic Chemically Peculiar stars in the Orion OB1 association, Monthly Notices of the Royal Astronomical Society, 2022, Volume 515, Issue 1, pp. 998-1011

Discovery of new LBVs in the Local Volume galaxy NGC 1156
Luminous Blue Variables (LBVs) are a rare type of massive stars with high luminosity and strong photometric and spectroscopic variability. Clarification of the nature and evolutionary status of LBVs requires a significant expansion of the sample of known and studied stars of this type. In the galaxy NGC1156, we discovered two massive stars with 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 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), 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 solar radii.
Authors: Solovyeva Yu. N., Vinokurov A.S., Tikhonov N.A., Kostenkov A.E., Sarkisyan A.N., Dedov E.O., Moiseev A.V., Oparin D.V. (SAO RAS) in cooperation with Atapin K.E. (SAO RAS, SAI MSU), Fabrika S.N. (SAO RAS, KFU), Valeev A.F. (SAO RAS, CrAO RAS)
Published:
1. Solovyeva, A. Kostenkov, E. Dedov, A. Vinokurov, Wind parameters of the new LBV in NGC1156, The Multifaceted Universe: Theory and Observations - 2022, 23-27 May 2022, SAO RAS, Nizhny Arkhyz, Russia; published December 14, 2022. Online at https://pos.sissa.it/cgi-bin/reader/conf.cgi?confid=425, id.49
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, 2023, Volume 518, Issue 3, pp.4345-4356, DOI: 10.1093/mnras/stac3408
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