几个河外射电源第二历元的327MHz VLBI观测

１９９１年３月，我们利用上海２５ｍ射电望远镜和欧洲ＶＬＢＩ网联合对几个河外射电源进行了第二历元的３２７ＭＨｚＶＬＢＩ观测．数据的相关处理先后在上海天文台三台站ＭＫ２相关处理机和美国的Ｃａｌｔｅｃｈ／ＪＰＬ相关处理机进行，以便于比较相关结果。本文给出３Ｃ８４、３Ｃ３４５和３Ｃ３８０的混合图。与第一历元的观测比较，３Ｃ３４５和３Ｃ３８０的流量密度没有明显的变化，但３Ｃ３４５的结构变化明显。３Ｃ８４和３Ｃ３４５有喷流的迹象．３Ｃ４５４．３的总流量在不到两年的时间内增加了２５％，如果这个变化是内禀的话，那么可能意味着一次新的流量爆发。

Second Epoch of 327 MHz VLBI Observations of Several Extragalactic Radio Sources

e present the second epoch VLBI observations of 3C84,3C345,3C380 and 3C454.3 at 327MHz with the Shanghai radio telescope and EVN in March 1991.Correlation was made in Shanghai as well as in Caltech/JPL for comparison.The hybrid maps of 3C84,3C345,and 3C380 are shown.No significant changes in the flux density of 3C345 and 3C380 are found by comparing with the first epoch observations.However,there is an obvious change in the structure of 3C345. 3C84 and 3C345 appeared to have jets.An increase of 25 percent in the flux density of 3C454.3 in less than two years indicate that a new outburst has probably occurred if the variation is intrinsic.