First detection of the SiO (v=3, J=2-1)maser emission from χ cygni

From the simultaneous observations of SiO nu = 3, J = 2-1 and J = 3-2 masers, SiO nu = 3, J = 2-1 maser emission was detected for the first time toward the S-type Mira variable chi Cyg. The line was a single spike and was redshifted with respect to the stellar velocity. The SiO nu = 3, J 3-2 maser emission was not detected from this star. However, for the O-rich Mira variable TX Cam, SiO nu = 3, J = 3-2 maser emission was detected, while v 3, J = 2-1 maser was not detected. Two possible line overlaps were adopted as an explanation of these observational results.