宇宙水分子脉泽谱线接收系统和观测研究

Spectral Receiving System at λ = 13 mm in Urumqi Observatory and Water Maser Observations

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５０ 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（ＣＺＦ）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６７ｕｓ，工作效率为 １００％．利用这套系统已观测到了一批Ｈ２Ｏ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 receing 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 67us sampling the per a fare 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 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.