Observational Study of the Galactic Nuclear Disk using SiO Masers

在2001-2003年的一项为期三年的研究中，我们进行了以下观察。1.利用多波束接收器对银河系中心20角分范围内的SiO脉泽源进行了浅层探测。2.对银核SiO脉泽中300个大幅值变星的观测。3.SgrA^*和周围SiO脉泽源的VLBA观测。S.Deguchi主要关注观测1和2，以及相关的数据缩减，M.Miyoshi关注观测3。对于观测1和2，我们发现有几颗恒星具有很高的径向速度，并且旋转速度场由两个分量组成。通过对银河系中心SIO脉泽的监测观测，我们发现与IRS10有关的脉泽在2002年5-12月期间再次爆发。因此，我们在2003年1月再次进行了VLBI观测。这些数据目前正在由Miyoshi先生处理。从2000年7月的观测中，我们得到了IRS 10相对于SGR A^*的自行。此外，我们还进行了SgrA^*的高分辨率成像。根据这一分析，SgrA^*的强度和发射分布在几个小时内发生变化。因为这是由于SgrA^*耀斑引起的，所以我们在世界上首次发现了SgrA^*耀斑的变化。这些新成果在夏威夷举行的国际研讨会上公布。我们仍然有几个大幅度变星没有观测到，并将在今年夏天完成观测。

In a three-year research during 2001-2003, we performed the following observations. 1. A shallow survey of SiO maser sources in a area of 20 arcminutes toward the galactic center using a multi-beam receiver. 2. A survey of300 Large Amplitude Variables in SiO masers in the Galactic nuclear disk. 3. VLBA observations of Sgr A^* and SiO maser sources around it. S. Deguchi mainly concerned with observations 1 and 2, and associated data reductions, and M. Miyoshi concerned with the observation 3. With observations 1 and 2, we found that there are several stars with very high radial velocities, and that the rotational velocity field consists of two components. With monitoring observations of the Galactic center SiO masers, we found that the masers associated with IRs10 flared again during May - December 2002. Therefore, we made VLBI observations again in 2003 January. The data are now under processing by M. Miyoshi. From the observations made in July 2000, we obtained the proper motion of IRs10 relative to Sgr A^*. In addition, we performed the high resolution imaging of Sgr A^*. According to this analysis, it was tuend out that the intensity and emission distribution of Sgr A^* varies within a few hours. Because this is due to flares of Sgr A^*, we discovered the variation of the Sgr A^* flare first in the world. These new results were presented in the international symposium at Hawaii. We still have several Large Amplitude Variables unobserved and will finish observations this summer.