Evolution of OH Maser Emission in the Active Star-Forming Region W75N. I. Research in the 1665 MHz Lineстатья
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Дата последнего поиска статьи во внешних источниках: 9 апреля 2021 г.
Аннотация:The monitoring results of the OH maser source in W75 N in the main line at 1665 MHz performedin 2007–2020 using the Nançay Radio Telescope (France) are presented. Generally, the maser in 2007–2009is characterized by a high activity. During the monitoring, time variations of the Stokes parameters werefound for all spectral features in the radial velocity range from –1 to 14 km/s. We found that its positionalangle and the degree of linear polarization , as well as the degree of circular polarization of most features,change with time according to certain regularities, not chaotically. Or they can change very weakly andthere is a correlation with the variability of the flux density. In this case, the radial velocities of the featureschange very little. It is shown that the main feature at 12 km/s during 50 years since the discovery of the OHmaser in W75 N had two maxima of activity with an interval of about 30 years between them. The identificationof spectral features in the 1665 MHz line with maser spots on VLBA maps has been carried out. Weshowed that a strong flare of the main features in 2007–2009 occurred in the VLA 2 source. During this flare,small changes in the angle and significant changes in the degree of both linear and circular polarization offeatures at 1.75, 2.1, and 3.05 km/s were observed. For the 0.65 km/s feature, significant changes in all emissionparameters were observed. The emission in the 1612 MHz satellite line is broadband. The broadening ofthe line to 1.9 km/s indicates that, in addition to thermal motion of matter, there is also turbulent motion ofmatter in the medium.