Japanese VLBI Network observations of SiO masers in the M-Type giant IRC -10414

Abstract

We present two-epoch maps of SiO masers (v = 1 and v = 2, J - 1-0) associated with the M-type star IRC -10414, which were obtained with the Japanese VLBI Network (JVN). The spatial and Doppler velocity distributions, and the intensity ratio of the v = 1 to v = 2 (J = 1-0) lines have significantly changed for eight years since our previous Very Long Baseline Array (VLBA) observation. The maser proper motions revealed by these twoepoch observations with an interval of one month are quite random and too fast to be explained by ballistic motions of the maser clumps. The maser distributions seen in the present observations cannot be explained by a rotatinginfalling ring model implied in the previous work. We discuss the kinematical relation between the SiO and H2O masers in IRC -10414. In the present observations, the scale sizes of SiO v = 1 and v = 2 masers in IRC -10414 were roughly equal, as observed in typical Mira variables. © 2008. Astronomical Society of Japan.