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

• Published in: Publications of the Astronomical Society of Japan 2012-12, Vol.64 (6)
• Main Authors: Imai, Hiroshi, Oyadomari, Miyako, Chong, Sze Ning, Nakagawa, Akiharu, Kurayama, Tomoharu, Nakashima, Jun-ichi, Matsumoto, Naoko, Nagayama, Takumi, Oyama, Tomoaki, Mizuno, Shota, Deguchi, Shuji, Cho, Se-Hyung
• Format: Article
• Language: English
• ISSN: 0004-6264; 2053-051X
• DOI: 10.1093/pasj/64.6.L6

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.