Monitoring and High-Resolution Studies of Some Hydroxyl and Methanol Masers in the High Mass Star Forming Region G9.62 + 0.20 E

Abstract

This thesis presents the observational data reduction and results of an investigation into the 1:6 GHz OH and 6:7 GHz methanol masers in the G9:62+0:20E massive star forming region. Monitoring observations from the Hartebeesthoek Radio Astronomy Observatory (HartRAO) radio telescope were employed to establish correlated variabilities between the 6:7 GHz methanol masers and the left and right circular polarizations (LCP and RCP) of the mainline 1:6 GHz OH masers. This is the first reported incidence of periodic variations of the LCP and RCP components of the 1:6 GHz OH mainline masers associated with the 6:7 GHz methanol masers in this high mass star forming region. Correlated variability between the varying features in the LCP components of both hydroxyl masers and methanol masers was observed but the variability profiles were different for both species. Time lags were recorded between the methanol and the OH maser variabilties. Within the OH masers the variability profiles were preceded by a dip in flux density. The first high resolution observation of the L-band and Cband continuum of G9:62+0:20E were conducted with the e-MERLIN interferometric array. A flux density of 2:25 0:20 mJy and an angular size of 130 mas were measured for the C-band continuum. At L-band, an upper limit of 162 mJy on the integrated flux density was calculated at the position of the continuum. These results unlike previous observations reveal that the spectrum turns over steeply at low frequencies which could be explained with a truncated inverse square law density distribution model. The peak brightness temperature indicates that the continuum is optically thin at C-band and optically thick at L-band. In the context of the colliding wind binary model for periodic maser sources it is the variation of the seed photons from the background HII region that explains the variability. The continuum results in this thesis place firm constraints on models of the HII region that can be used to test the predictions of the colliding wind binary model in terms of the variability profiles of the OH and methanol masers.