²⁸SiO j=1-0, v=1, 2 & 3 maser emission from AGB stars

Paper in proceeding, 2012

The v=1, 2 J=1–0 and v=1 J=2–1 are intense SiO masers, often mapped in AGB stars. Their distribution displays ring-like structures in the regions close to the star. The distribution of the v=1, 2 J=1–0 masers are similar, but the spots are rarely coincident. The v=1 J=2–1 maser ar-rises, however, from a well separated region. It has been argued that this difference can only be explained by models including overlap of two IR lines of SiO and H2O. The v=3 J=1–0 line is not expected to be affected by any line overlap, and its spot structure should be that predicted by the standard models. Our first results on the relative positions of the three lines are surprising but yet consistent with current models including line overlap.