射电天文研究室知识库

详细分析了13 mm谱线接收系统的结构和这个系统设计的独特之处．接收机是制冷 的HEMT接收系统，工作温度为20 K，噪声温度为5O K，带宽为2GHz。频谱分析终端是一架 基于付里叶线性调频z变换(CZT)的声表面波频谱仪(SAW)，总带宽为40 MHz，频率分辨率为 40kHz，每帧输出为67 微秒，工作教率为100％．利用这套系统已观测到了一批水脉泽源．发现 有的源有激烈的变化．

A new radio spectral receiving system has installed on the 25 m radio telescope of the Urumqi Astronomical Observatory. Its special designs and structure are presented in deatail. The receivre is a cryogenically cooled HEMT receivng system with a 2 GHz wide band, a 20 K working temperature and an average noise temperature of 50 K. The back end is a surface acoustic wave(SAW) chirp-transform spectrum analyzing system with a total bandwidth of 40 MHz, a frequency resolution of ~40 kHz, a 100% working duty cycle and a 67μs sampling time per a frame spectrum.
After carefully calibrations of the line observations we observed water maser emission from a number of the known H₂O maser sources. We found that there are dramatic changes in VY CMa spectrum in the comparison with the early epoch observations. The spectrum appears to consist of two striking like groups and each group has three features. The appearances and the ratio of these three features are very similar in the two maser groups. All of the H₂O maser features are red-shifted with respect to the VY CMa stellar velocity of 17.6 km^-1.