Search for High Energy Gamma-ray Sources in the Southern Sky

大麦哲伦星云中的超新星1987A为研究年轻超新星的粒子发射和电磁辐射提供了第一次机会。在膨胀的喷射物中心，一颗快速旋转的磁化中子星可能是超高能量（UHE）宇宙射线的强大来源。H. Sato指出，高能伽马射线可能是由中子星加速的强子与超新星喷射物碰撞产生的衰变介子产生的。我们在新西兰的Black Birch（海拔1640 m， 41 45s, 173 47e）安装了伽玛射线探测器。计数器阵列由76个闪烁探测器组成。观测开始于1987年10月13日。根据1987-1991年的资料，得出SN1987A （>00 TeV）的UHE γ射线通量上限为4X10^<-14> cm^<-2> sec^<-1>。SN1987A发射的3 TeV以上的伽马射线已经用3个切伦科夫反射镜进行了搜索，数据给出了通量的上限为5X10^<-12> cm^<-2> sec^<-1>。在1988年1月14日和15日的数据中发现了多余的计数，对应于通量（1.9<正负>0.5）X10^<-11> cm^<-2> sec^<-1>。观测到的过量时间与Ginga卫星探测到的x射线耀斑时间一致。最近，我们搜索了来自南方天体的UHE伽马射线，包括半人马座A、船帆座X-1、半人马座X-3、银河系X-1以及麦哲伦星云中的一些天体。这些来源都没有显示出明显的过剩事件。观察仍在进行中。利用月球的阴影效应来测量探测器的角分辨率。在月球中心的事件密度已被发现低于近月球方向的事件密度。

The supernova 1987A in the Large Magellanic Cloud has provided the first opportunity to study the emission of particles and electromagnetic radiation from a young supernova. A rapidly rotating, magnetized neutron star at the center of the expanding ejecta may be a powerful source of ultra high-energy (UHE) cosmic rays. H. Sato has pointed out that high energy gamma-rays may be produced from the decay pions generated by the collisions of hadrons accelerated by the neutron star with supernova ejecta. We installed gamma-ray detectors at the Black Birch in New Zealand (1640 m above sea level, 41ﾟ45'S, 173ﾟ47'E). The counter array consists of 76 scintillation detectors. The observations started on 13 October 1987. An upper limit on tile flux of UHE gamma-rays from SN1987A (>100 TeV) was obtained to be 4X10^<-14> cm^<-2> sec^<-1> from the data of 1987-1991. gamma-rays above 3 TeV emitted by SN1987A have been searched for using three, Cerenkov mirrors and data give an upper bound on the flux of 5X10^<-12> cm^<-2> sec^<-1>. Data on January 14 and 15 1988 were found to have excess counts corresponding to a flux of (1.9<plus-minus>0.5)X10^<-11> cm^<-2> sec^<-1>. The observed time of the excess coincides with the time of X-ray flare detected by the Ginga Satellite.Recently, we have searched for UHE gamma-ray from Southern objects including Cen A, Vela X-1, Cen X-3, Cir X-1 and also several objects in the Magellanic Clouds. None of these sources shows significant excess events. The observation is still being carried out.The moon was used to measure the angular resolution of the detector through its shadowing effect. The density of the events at the center of the moon has been found to be lower than event density near direction of the moon.