The first simultaneous mapping of four 7 mm SiO maser lines using the OCTAVE system

We report on simultaneous very long baseline interferometry (VLBI) mapping of (SiO)-Si-28 v = 1, 2, 3, and (SiO)-Si-29 v = 0 J = 1 -> 0 maser lines at the 7 mm band toward the semiregular variable star, WHydrae (WHya), using the new data acquisition system (OCTAVEDAS), installed in the VLBI Exploration of Radio Astrometry (VERA) array and temporarily operated in the 45 m telescope of the Nobeyama Radio Observatory. Although these masers were spatially resolved, their compact maser spots were fortunately detected in the 1000 km baselines of VERA. We found the locations of the v = 3 maser emission which are unexpected from the currently proposed maser pumping models. Mapping of the (SiO)-Si-29 maser line in W Hya is the third result after those in WX Psc and R Leo. This paper shows the scientific implication of simultaneous VLBI observations of multiple SiO maser lines as realized by using the OCTAVE system.