Observations of SiO Maser Sources within a Few Parsec from the Galactic Center
Observations of SiO Maser Sources within a Few Parsec from the Galactic Center
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距银河系中心几秒差距内 SiO 脉泽源的观测
DOI：
10.1093/pasj/54.1.61
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发表时间：
2002
影响因子：
2.3
通讯作者：
J. Nakashima
中科院分区：
文献类型：
--
作者：
S. Deguchi;T. Fujii;M. Miyoshi;J. Nakashima
用43 GHz的Nobeyama 45米望远镜对银河系中心附近的SiO脉泽源进行了测绘和监测观测。在一个30“的网格中绘制了一个大约200”x 100“的矩形图，在一个20”的网格中向银河系中心绘制了一个三角形图，结果发现了15个SiO源;除了一些微弱的源外，获得了源的位置，误差在5- 10“之间。通过3年的观测观测发现，2000年3 - 5月IRS 10 EE的Vlsr =-27km/s分量约为1.5Jy，比正常亮度高5倍以上。使用SiO源的径向速度和位置，我们确定了5个是以前观察到的OH 1612 MHz源的对应物。其他10个SiO源没有OH对应物，但有两个先前用VLA检测到，四个位于近红外波长处观察到的大振幅变量的位置附近。用最小二乘法拟合速度与银河系半径的关系曲线，可以得出星星团绕银河系中心旋转的速度相当高。观测到的径向速度色散与以前获得的值大致一致。结果发现，所有的SiO源与OH 1612兆赫对应的光变周期长于450天，而SiO源没有OH脉泽往往有周期短于450天。这一事实表明，较低质量的AGB星更经常检测到SiO脉泽比OH 1612 MHz线。
Mapping and monitoring observations of SiO maser sources near the Galactic center were made with the Nobeyama 45-m telescope at 43 GHz. Rectangular mapping an area of approximately 200'' x 100''$ in a 30'' grid, and triangular mapping in a 20'' grid toward the Galactic center, resulted in 15 detections of SiO sources; the positions of the sources were obtained with errors of 5--10'', except for a few weak sources. Three-year monitoring observations found that the component at V_lsr=-27 km/s of IRS 10 EE flared to about 1.5 Jy during 2000 March--May, which was a factor of more than 5 brighter than its normal intensity. Using the radial velocities and positions of the SiO sources, we identified 5 which are counterparts of previously observed OH 1612 MHz sources. The other 10 SiO sources have no OH counterparts, but two were previously detected with VLA, and four are located close to the positions of large-amplitude variables observed at near-infrared wavelengths. A least-squares fit to a plot of velocities versus Galactic longitudes gives a rather high speed for the rotation of the star cluster around the Galactic center. The observed radial-velocity dispersion is roughly consistent with a value obtained before. It was found that all of the SiO sources with OH 1612 MHz counterparts have periods of light variation longer than 450 days, while SiO sources without OH masers often have periods shorter than 450 days. This fact suggests that lower-mass AGB stars are more often detected in SiO masers than in the OH 1612 MHz line.