First VLBI mapping of circumstellar 29 SiO maser emission

We report the first VLBI map of the v=0 J=1–0 maser line of 29 SiO in the long-period variable star IRC +10011. We have found that this maser emission is composed of multiple spots distributed in an incomplete ring, suggesting that this maser is also amplified tangentially, as already proposed in other SiO circumstellar masers. We present also VLBI maps for the 7 mm 28 SiO v=1 and 2 J=1–0 and the 3 mm v=1 J=2–1 lines. The 29 SiO masing region appears to be located in a layer in between the 28 SiO v=1 J=1–0 and 28 SiO v=1 J=2–1 lines. In addition, we confirm that the 86 GHz maser v=1 J=2–1 forms in an outer region of the circumstellar envelope compared to the other 28 SiO masers studied. Finally, we discuss the possible implications of the observational results on the SiO maser pumping theory.