A Study of Variability of the Stokes Parameters and the Magnetic Field of G43.8–0.1 in the OH Line 1665 MHz

Abstract

We present results of the study of maser emission variability in the 1665 MHz OH line in the G43.8–0.1 star formation region based on observations (monitoring) in 2008–2022 at the Large Radio Telescope in Nancy (France). Variability of all polarization parameters of the majority of spectral features, which has a monotonic regular character, has been found. Spatial identification of the main spectral features of the OH 1665 MHz line with maser spots (condensations) on the VLA map has been carried out. For the Zeeman pair VLSR=44.15 km/s, a monotonic change of the splitting with time during 2008–2022 was found and, consequently, a change of the magnitude of the longitudinal magnetic field. According to our calculations, at the end of 2012, the direction of the magnetic field changed to the opposite. Сorrelated with H∥, there were changes in the angle χ and, as a consequence, changes in the direction of the vector of the transverse magnetic field H⊥0. For the maser feature at 44.5 km/s, a change of H⊥ by 180° was found. In 2016–2022, some reorientation of the global magnetic field (H⊥) in G43.8–0.1 occurred. The field became less chaotic: in the eastern part, the field in maser condensations is perpendicular to the arc, and in the western part, it is parallel to the arc. It is assumed that the global magnetic field in the entire U H II region of the G43.8–0.1 source has the same direction: along the axis (northeast)—(southwest).