On the periodic class II methanol masers in the high mass star forming region G9.62+0.20E
Centre for Space Research, North-West University, Potchefstroom, 2520, South Africa, johan.vanderwalt@nwu.ac.za
Abstract
Class II methanol masers are known to be exclusively associated with high mass star forming regions. The phenomenon of periodic methanol masers associated with a small number of star forming regions is now known for a number of years. The underlying process(es) responsible for the periodicity is not known however. In this paper I present a simple colliding-wind scenario to try explain the periodicity and the flare profiles of the periodic flaring of the class II masers in the high-mass star forming region G9.62+0.02E. It is found that the 12.2 GHz methanol maser time series as well as the profiles of individual flares are reproduced very well under the assumption that the observed flaring is due to changes in the free-free background emission from the H II region. A number of other properties of the masers can also be explained within the framework of this model. It is concluded that a colliding-wind binary is a possible underlying cause for the periodic class II masers inG9.62+0.20E and should be investigated further.