Japanese VLBI network observations of 6.7-GHz methanol masers II. Results

摘要

We are using a Japanese VLBI network (JVN) for VLBI observations of 6.7-GHz methanol masers associated with massive star-forming regions. Here we present results for Cepheus A (Cep A) from observations taken on September 9, 2006. The distribution of the maser spots indicates either a spherical bubble or a disk having an inclination of several tens degree. We construct a disk model with an inclination of ～70° and a radius of ～700 AU. From a luminosity of 1.7 x 10~4 L_⊙ for a source observed in this region, the excitation of the maser is probably radiative.