SiO Maser Sources within 30 pc of the Galactic Center

Shuji Deguchi1 and Hiroshi Imai2

1 Nobeyama Radio Observatory, Minamimaki, Minamisaku, Nagano 384-1305, Japan
2 JIVE, PO Box 2, Dwingeloo 7990, The Netherlands


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see PASJ 54, L19; PASJ 54, 61

Mass losing AGB stars are good probes of the Galactic center. Using Nobeyama 45-m radio telescope, we have observed about 300 large amplitude variables within 30 pc of the Galactic center with SiO maser lines. Resulting detections gave the radial velocities of 197 stars; light-variation periods have been known for all of these stars (Glass et al. 2001). The SiO detection rate increases sharply with the period and it is about twice of the OH maser detection rate. The radial-velocity data show slow and rapid rotations of the outer and inner circumnuclear-disk stars, respectively. The rotation axis of the stellar system, however, does not seem to be bent more than 10 degree to the Galactic rotation axis for subsets of the sample. No period/mass segregation was found in the sample. Five high-velocity stars were detected only at the negative-longitude side of the Galactic center. The observations indicate that these stars were formed in clusters of stars in the nuclear disk and were dispersed to the bulge.