Study of Gamma-ray Bursts by the Cooperation with the Satellites and the Ground Based Observatories

我们研制了两种仪器，它们的主要目的是观测伽马射线暴。一个是高能瞬变探测卫星（HETE-II），另一个是国际空间站上的全天空x射线图像监视器（MAXI）。HETE-II卫星于2000年10月9日发射，成功进入轨道。我们从1997年就开始准备发射这颗卫星。为了提高仪器的检测效率和背景抑制效率，对仪器的设计进行了细微的改变。进行了多种环境试验或性能试验。在发射后的多次初始性能测试中，我们获得了探测器的在轨标定数据。现在我们开始进行正常的观察。截至2001年3月26日，共发现了20个候选伽玛暴事件，其中10个事件通过其他观测得到了证实。我们还与HETE-II卫星合作，在宫崎大学楼顶搭建了光学跟踪观测系统。当HETE-II发现伽马暴时，它会向地面发送伽马暴的位置信息。这些信息将很快通过互联网被计算机接收。然后计算机控制系统，用小型望远镜开始后续观测。该系统获得的数据将与以前获得的数据或编目数据进行比较。我们发现我们可以自动探测到一个比18等更亮的未知物体，只需要曝光大约10秒。我们不仅开发了观测系统，还对日本卫星的观测资料进行了分析。我们在伽马射线暴的x射线光谱中发现了两个膝盖。这意味着伽马射线暴的光谱变化的可能性。

We have developed two kinds of instrument whose prime purpose is observing the gamma-ray bursts. One is HETE-II (High Energy Transient Explorer II) satellite, the other is MAXI (Monitor of All sky X-ray Image) onboard international space station. HETE-II satellite was launched on October 9th 2000 and was successfully enterd into the orbit. We have prepared for launching this satellite since 1997. The design of the instrument was slightly changed to improve the detection efficiency and the background rejection efficiency than those of the former one which was failed to operate. Many kinds of environmental test or performance test were carried out.For the duration of many test for initial performance after its launch, we have obtained in-orbit calibration data of detectors. Now we have started the normal observation. As of March 26th 2001, 20 candidates for gamma-ray burst were discoverd and 10 events among them were confirmed by other observations.We have also constructed the optical follow-up observation system in cooperation with HETE-II satellite on the rooftop of the builing in Miyazaki university. When HETE-II discovers a gamma-ray burst, it sends the position information of gamma-ray burst to the ground. This information will be received by the computer through the internet soon. Then the conputer controls the system to start the follow-up observation using a small telescope. The obtained data by this system will be compared with one obtained previosly or the catalogued data. We found that we can detect automatically an unknown object brighter than 18th magnutude using the exposure about 10 seconds.We have not only developed an observational system, but also analized the observational data obtained by japanese satellite. We found two knees in the x-ray spectrum of a gamma-ray burst. This means the possibility of spectral variability of the gamma-ray burst.