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

Abstract

The recently discovered strong emission lines at 86.24 GHz (~3.48 mm) 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. We have detected 12 maser sources, and almost all are late M-type Mira or semiregular variables. Many of the known 0H/H 2 0/IR sources are also SiO maser sources, and good velocity correlations between SiO and H 2 0 emission profiles were found. Characteristics of these new SiO maser sources are discussed.