Pilot VLBI Survey of SiO v = 3 J = 1 → 0 Maser Emission around Evolved Stars

Abstract

Abstract In this letter, we report on detections of SiO $ v$$ =$ 3 $ J$$ =$ 1$ \rightarrow$ 0 maser emission in very long-baseline interferometric (VLBI) observations towards 4 out of 12 long-period variable stars: WX Psc, R Leo, W Hya, and T Cep. The detections towards WX Psc and T Cep are new ones. We also present successful astrometric observations of SiO $ v$$ =$ 2 and $ v$$ =$ 3 $ J$$ =$ 1$ \rightarrow$ 0 maser emissions associated with two stars: WX Psc and W Hya and their position-reference continuum sources: J010746.0$ +$ 131205 and J135146.8$-$ 291218 with the VLBI Exploration of Radio Astrometry (VERA). The relative coordinates of the position-reference continuum source and SiO $ v$$ =$ 3 maser spots were measured with respect to those of an SiO $ v$$ =$ 2 maser spot adopted as a fringe-phase reference. Thus, the faint continuum sources were inversely phase-referenced to the bright maser sources. This implies possible registration of multiple SiO maser line maps onto a common coordinate system with 10 microarcsecond-level accuracy.