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

1)我们在银河系中心的大质量黑洞SgrA* 周围进行了几个SiO脉泽的VLBA观测。我们探测到了其中三个的自行，精度约为0.1mas/年。结果表明，SgrA* 可能相对于周围的恒星移动。我们还发现，距离银河系中心2 pc以内的质量下限是2*10^6太阳质量。2）使用野边山毫米波干涉仪，我们监测了SgrA* 的短时间耀斑通量密度。3）通过对晚型星SiO脉泽辐射视线速度的统计分析，利用Bolzmann方程沿视线沿着积分，得到了银河系中心30 pc以内的质量（包括暗物质）。与OH脉泽的分布不同，SiO脉泽的分布遵循与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，并满足平方定律，由Bolzmann方程的视线积分，可得到银河系中心质量的动量-速度方程：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.