Mapping and monitoring observations of SiO maser sources near the Galactic center were made with the Nobeyama 45-m telescope at 43 GHz .
Rectangular mapping an area of approximately 200 ^ { \prime \prime } \times 100 ^ { \prime \prime } in a 30 ^ { \prime \prime } grid , and triangular mapping in a 20 ^ { \prime \prime } grid toward the Galactic center , resulted in 15 detections of SiO sources ; the positions of the sources were obtained with errors of 5–10 ^ { \prime \prime } , except for a few weak sources .
Three-year monitoring observations found that the component at V _ { lsr } = -27 km s ^ { -1 } of IRS 10 EE flared to about 1.5 Jy during 2000 March–May , which was a factor of more than 5 brighter than its normal intensity .
Using the radial velocities and positions of the SiO sources , we identified 5 which are counterparts of previously observed OH 1612 MHz sources .
The other 10 SiO sources have no OH counterparts , but two were previously detected with VLA , and four are located close to the positions of large-amplitude variables observed at near-infrared wavelengths .
A least-squares fit to a plot of velocities versus Galactic longitudes gives a rather high speed for the rotation of the star cluster around the Galactic center .
The observed radial-velocity dispersion is roughly consistent with a value obtained before .
It was found that all of the SiO sources with OH 1612 MHz counterparts have periods of light variation longer than 450 days , while SiO sources without OH masers often have periods shorter than 450 days .
This fact suggests that lower-mass AGB stars are more often detected in SiO masers than in the OH 1612 MHz line .