Vibrationally excited SiO - A new type of maser source in the millimeter wavelength region

The recently discovered strong emission lines at 86.24 GHz from the J = 2-1 rotational transition of SiO in its first excited vibrational state have been found to be a maser source associated with infrared stars. Twelve maser sources have been detected, and almost all are late M-type Mira or semiregular variables. Many of the known OH/H2O/IR sources are also SiO maser sources, and good velocity correlations between SiO and H2O emission profiles were found. Characteristics of these new SiO maser sources are discussed.