Evolution of the OH and H2O Maser Emission in the Active Star-Forming Region IRAS 05358+3543 (S231)

Authors
• 1 Moscow State University, Sternberg Astronomical Institute, Moscow, 119234, Russia , Moscow (Russia)
• 2 Observatoire de Paris-Meudon, CNRS, UPMC, Universite’ Paris-Diderot, Meudon Cedex, 92195, France , Meudon Cedex (France)
• 3 Astro Space Center, Lebedev Physical Institute, Russian Academy of Sciences, Moscow, 119991, Russia , Moscow (Russia)
• 4 Pushchino Radio Astronomy Observatory (PRAO), Astro Space Center, Lebedev Physical Institute, Russian Academy of Sciences, Pushchino, Moscow region, 142290, Russia , Pushchino (Russia)
Type
Published Article
Journal
Astronomy Reports
Publisher
Pleiades Publishing
Publication Date
Oct 10, 2020
Volume
64
Issue
10
Pages
839–854
Identifiers
DOI: 10.1134/S1063772920110013
Source
Springer Nature
License
Yellow

Abstract

AbstractWe present the results of our observations of the star-forming region located in the Perseus arm and associated with the Sharpless nebula S231 in the lines of H2O at a wavelength of 1.35 cm and OH at a wavelength of 18 cm obtained with the Pushchino 22-m radio telescope (Russia) and the Nançay Large Radio Telescope (France), respectively. We provide a catalog of H2O maser spectra in the period from March 2003 to March 2020. The variability of the integrated flux that we have calculated based on the monitoring by Felli et al. (1987–2007) and our monitoring (2003–2020) has a quasi-cyclic pattern with a cycle duration from 4.3 to 7.7 yr. Flares of maser emission of both single and several features occurred in each activity cycle. The mean rise and decay times of the flare emission were \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$0.30 \pm 0.02$$\end{document} and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$0.35 \pm 0.02$$\end{document} yr, respectively. The observed radial velocity drift and jumps of the H2O emission features can be a consequence of the impact of shocks emerging as the protostar activity rises on them. The complex pattern of variability shows that the H2O masing medium is fragmented and small-scale turbulent motions of matter can occur in it. We have observed the OH maser emission in the 1665 and 1667 MHz main lines and the 1720 MHz satellite line. A large number of OH emission features and their variability have been detected. We have found one Zeeman pair at ‒9.2 km/s with a small splitting, with the longitudinal magnetic field in the period 2008–2020 having decreased monotonically from 0.24 to 0.10 mG. For the three most intense features we have calculated the degrees of linear polarization and position angles. A correlation between the H2O and OH maser activities has been found.

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