Gamma-Ray Pulsars
Gamma-Ray Pulsars
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DOI：
10.1007/978-3-662-04593-0_6
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发表时间：
2002-09
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影响因子：
--
通讯作者：
G. Kanbach
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文献类型：
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作者：
G. Kanbach
1967年，一台新的射电望远镜在英国投入使用。在剑桥大学安东尼·休伊什的指导下，一组天文学家完成了这一接收器系统，以研究新发现的准恒星射电源，以及来自遥远宇宙点源的无线电波通过湍急的星际和星际等离子体时产生的快速闪烁。其中一个目标是研究这些宇宙等离子体云的特性，因此在81.5兆赫的灵敏接收器上安装了一个高速记录器。天体源通过无线电接收器固定视场的强度被记录在条形图上，并必须通过目测进行分析。这项任务自然而然地落到了该小组的研究生乔斯林·贝尔身上。1967年8月6日，她第一次注意到右升角19时19分的天空穿过视场时出现了一串特殊的无线电信号。是什么导致了如此短暂的周期性信号？第一个怀疑当然是一些电子设备的干扰，比如路过的汽车或卫星的点火。但令贝尔惊讶的是，这个信号几乎在一天中的同一时间再次出现。几个月后，很明显，规则的脉冲来自我们太阳系以外的天体来源。此外，1967年11月28日的亚秒级时间分辨率的震源记录显示，脉冲以1.33%S的规则周期重复。当时--这一现象的发现仍然保密--人们认真考虑了来自外星文明的无线电信号被记录下来的想法，代号为“LGM”(小绿人)。在天空的不同位置和不同周期又发现了三个脉动源，废除了末次盛冰场假说，很明显，一种令人着迷的新自然现象很快被发现，称为脉冲星。Hewish等人(1968)的这份出版物，除了介绍了CP1919(剑桥脉冲星的CP)的观测结果外，还讨论了两种可能的解释：白矮星的规则振荡和“致密”恒星的自转。世界各地的射电天文台立即开始了对这些新天体的真正搜寻：几个装置具有必要的
In 1967 a new radio telescope was commissioned in England. A group of astronomers under the direction of Anthony Hewish at the University of Cambridge had completed this receiver system to study the newly discovered quasi stellar radio sources and the rapid scintillations that result when radio waves from distant cosmic point sources pass through the turbulent interstellar and interplanetary plasma. One goal was to study the properties of these cosmic plasma clouds, and the sensitive receiver at 81.5 MHz was therefore fitted with a high-speed recorder. The intensity of celestial sources passing over the fixed field of radio receivers was recorded on strip charts and had to be analyzed by visual inspection. This task fell naturally to the graduate student of the group, Jocelyn Bell. On August 6, 1967, she first noticed a peculiar train of radio signals when the sky at right ascension 19h19min passed through the field of view. What could have caused such a transient periodic signal? The first suspicion was of course interference from some electric equipment, like the ignition of a passing car or a satellite. But to the surprise of Bell the signal appeared again at about the same time of day. After a few months it was obvious that the regular pulses were coming from a celestial source beyond our solar system. Furthermore a recording of the source with sub-second time resolution on November 28, 1967, revealed pulses repeating at a regular period of 1.33 s. At that point-the discovery of the phenomenon was still kept secret-the thought that radio signals from an extraterrestrial civilization had been recorded was seriously considered, under the code" LGM"(little green men). The discovery of three more pulsating sources at different locations in the sky and with different periodicities did away with the LGM hypothesis, and it became clear that a fascinating new natural phenomenon, soon called pulsars, had been discovered. The publication by Hewish et al.(1968), aside from presenting the observations of CP1919 (CP for Cambridge Pulsar), discussed two possible explanations: regular oscillations of white dwarfs and rotation of" compact" stars. Immediately a veritable hunt for these new astrophysical objects started at radio observatories around the world: several installations had the necessary