Kinematics of the v=1, J=1→0 SiO masers at 43 GHz towards TX Cam - a new 73-frame movie

Abstract

We present a new version of the movie of the SiO masers around the Mira variable TX Cam. It consists of 73 frames (60 observed epochs) with data covering almost two complete stellar cycles between 1997 May 24 and 2000 May 21. Observations were carried out using the Very Long Baseline Array in biweekly and later at monthly intervals. The purpose of this paper is to discuss the global properties of the emission in the extended atmosphere of the star as well as the kinematics of individual components. The existence of shock waves and their contribution to the morphology and the kinematics of the gas is also examined and compared with theoretical models. Contrary to the dominant expansion observed in the first cycle, both expansion and contraction are observed in the second cycle. The maser variability is correlated with the pulsation of the star but not with the optical intensity. Most of the individual components identified follow the behaviour of the ring, but there are exceptions with more complex three-dimensional trajectories.