Observational Study of the Massive Black Hole SgrA* and its Surrounding Field

1)我们在银河系中心对质量黑洞SgrA*周围的几个SiO脉泽进行了VLBA观测。我们探测到了其中三个的自行，精度约为0.1 Ma/年。结果表明，SgrA*可能会相对于周围的恒星运动。我们还发现，在距银心2pc的范围内，SgrA*的质量下限为2×10^6个太阳质量。2)利用Nobeama毫米波干涉仪对短时间耀斑的SgrA*的通量密度进行了监测。在2004年12月至2005.3-05月的观测期间，没有观测到SgrA*的耀斑)我们通过分析晚型恒星SiO脉泽发射的视线速度的统计，并利用玻尔兹曼方程沿视线的积分，得到了银心30pC内的质量(包括暗物质)。与OH脉泽的分布不同，其中一个SiO脉泽遵循距离银河系中心距离的平方。假设中心质量为中心黑洞质量与恒星系统质量之和，并服从平方定律，由玻尔兹曼方程的视线积分得到动量速度方程，银心质量为：MR=(2.69±1.30)+0.88[±0.07](R/PC)^{1.25)×10^6太阳质量。

1) We performed VLBA observations of several SiO masers around the massive black hole, SgrA* at the Galactic center. We detected proper motions of the three out of them with accuracy about 0.1mas/year. The results suggest that SgrA* may move relative to the surrounding stars. We also found the lower limit of the mass within 2 pc from the Galactic center is 2*10^6 solar mass.2) Using the Nobeyama Millimeter wave Interferometer we monitored the flux density of SgrA* for short time flaring. There observed no flare of SgrA* within the observing session from Dec 2004 to May 2005.3) We derived the mass (including dark matter) within 30 pc from the Galactic center by analyzing the statistics of line of sight velocities of SiO maser emissions from late type stars and by the use of integration of the Bolzmann equation along the line of sight. Unlike the distribution of OH masers, the one of the SiO masers follows the square of the distance from the Galactic center. Assuming that the central mass is the sum of the mass of central black hole and stellar system with the square law, we can make an equation of momentum of velocities from the line of sight integration of Bolzmann equation.The mass of the Galactic center is M R=(2.69±1.30]+0.88[±0.07](R/pc)^{1.25)×10^6 solar mass.