SIMULTANEOUS OBSERVATIONS OF SiO AND H2O MASERS TOWARD KNOWN STELLAR H2O MASER SOURCES

We present the results of simultaneous observations of SiO v = 1, 2, 29SiO v = 0, J = 1-0, and H2O 616-523 maser lines toward 152 known stellar H2O maser sources using the Yonsei 21 m radio telescope of the Korean VLBI Network from 2009 June to 2011 January. Both SiO and H2O masers were detected from 62 sources with a detection rate of 40.8%. The SiO-only maser emission without H2O maser detection was detected from 27 sources, while the H2O-only maser without SiO maser detection was detected from 22 sources. Therefore, the overall SiO maser emission was detected from 89 sources, resulting in a detection rate of 58.6%. We have identified 70 new detections of the SiO maser emission. For both H2O and SiO maser detected sources, the peak and integrated antenna temperatures of SiO masers are stronger than those of H2O masers in both Mira variables and OH/IR stars and the relative intensity ratios of H2O to SiO masers in OH/IR stars are larger than those in Mira variables. In addition, distributions of 152 observed sources were investigated in the IRAS two-color diagram.