| We carried out simultaneous observations of four maser lines, SiO v = 1, 2, 29SiO v = 0, J = 1-0, and H2O 616-523, toward 83 known SiO maser sources without H2O maser detections using the Korean VLBI Network single dish telescopes. Both SiO and H2O masers were detected from 14 sources, resulting in a detection rate of 16.9%. H2O maser emission without SiO maser emission was detected from one source. Therefore, H2O maser emission was newly detected from 15 sources. SiO maser emission without H2O detection was detected from 55 sources, which gives a total SiO maser detection rate of 83.1% when including sources that have both SiO and H2O maser emission detected. SiO v = 2 maser emission was detected from nine sources without v = 1 maser detection. The SiO v = 2 maser sources without the v = 1 maser detections need to be investigated, with a large number of v = 2 only maser sources related to the development of dust shells and their evolutionary sequence from asymptotic giant branch (AGB) to post-AGB stars. The average values of the peak and integrated antenna temperature ratios of H2O to SiO masers are 0.44 and 0.28 in the 14 sources that have both SiO and H2O detections. Observational characteristics of several individual sources are noted and the dependence of the different maser intensity ratios on the stellar phase is discussed. In addition, the observational results of SiO and H2O masers are discussed in IRAS two-color diagrams. |
