ATCA OBSERVATIONS OF SiO MASERS IN THE GALACTIC CENTER

Abstract

We present the Australia Telescope Compact Array observations of the SiO masers in the Galactic center (GC) in transitions of v = 1, J = 2-1 at 86 GHz and v = 1, J = 1-0 at 43 GHz. Two 86 GHz SiO masers were detected within the central parsec, and they are associated with IRS 10EE and IRS 15NE, respectively. We detected eighteen 43 GHz SiO masers within a projected separation of 2 pc from Sagittarius A*, among which seven masers are newly discovered from our observations. This raises the total number of 43 GHz SiO masers within the central 4 pc of the GC region to 22. Simultaneous observations at 86 and 43 GHz showed that the intensity of 43 GHz SiO maser is ~3 times higher than that of 86 GHz maser in IRS 10EE (an OH/IR star), while the integrated flux of the SiO maser emission at 43 GHz is comparable with that at 86 GHz in IRS 15NE (an ordinary Mira variable). These results are consistent with previous observations of massive late-type stars in the Galaxy in which the 86 GHz SiO maser is in general weaker than the 43 GHz SiO maser in OH/IR stars, while the two transitions are comparably strong in Mira stars.