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

大麦哲伦星云中的超新星1987 A首次提供了研究年轻超新星的粒子发射和电磁辐射的机会。在膨胀的喷出物中心，一颗快速旋转的磁化中子星星可能是超高能宇宙射线的强大来源。H.佐藤指出，高能伽马射线可能是由中子星星加速的强子与超新星喷出物碰撞产生的衰变π介子产生的。我们在新西兰的黑桦树（海拔1640米，南纬41度45分，东经173度47分）安装了伽马射线探测器。计数器阵列由76个闪烁探测器组成。观测于1987年10月13日开始。根据1987-1991年的数据，得到SN 1987 A（&gt;100 TeV）的UHE γ射线通量的上限为4 × 10 <-14><-2><-1>~（-1）cm ~（-1）sec ~（-1）。SN 1987 A发射的3 TeV以上的伽马射线已经用三个切伦科夫镜进行了搜索，数据给出的通量上限为5 × 10 ^<-12>cm^<-2>sec^<-1>。1988年1月14日和15日的数据被发现有对应于（1.9 <plus-minus>± 0.5）× 10 ^<-11>cm^<-2>sec^的通量的过量计数<-1>。最近，我们对南方天体包括Cen A、Vela X-1、Cen X-3、Cir X-1以及麦哲伦云中的几个天体进行了UHE γ射线探测。这些来源均未显示重大超额事件。观测工作仍在进行中，利用月球的遮蔽效应，测量了探测器的角分辨率。在月球中心的事件密度已被发现低于事件密度靠近月球的方向。

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.