STUDY ON GRAVITATIONAL WAVES FROM COALESCING BLACK-HOLE MACHO BINARIES

一个20米基线激光干涉仪引力波探测器从东京搬到了神冈矿，那里的地震噪音比东京低两个数量级，灵敏度和稳定性大大提高。所获得的位移灵敏度为1.2 × 10 ~ <-18>4 m/cm ~ 2<Hz>，与TAMA 300引力波探测器获得的世界最佳灵敏度相当。它的灵敏度也足以探测到来自距离地球1千秒差距以内、信噪比为10的致密双星星星聚并体的引力波。2001年的观测时间超过了2000小时，在选定的11天中，最佳观测率达到99.8%，这不仅得益于较低的地震噪声环境，而且得益于新安装的自启动系统。2001年夏天，我们还首次利用TAMA 300观测到了银河系中的致密星星（如一个BMO黑洞）双星的引力波。巧合的是，采集的数据总计长达709小时。用一步搜索法选出候选引力波后，用符合分析法检验了到达时间、质量参数和信噪比的一致性。作为初步结果，没有发现引力波信号，这一结果有望给引力波搜索提出新的上限。

A 20-m baseline laser interferometer gravitational wave detector was moved from Tokyo into the Kamioka mine, where the seismic noise was lower by two orders of magnitude than in Tokyo, and its sensitivity and stability were drastically improved. The obtained displacement sensitivity of 1.2 x 10^<-18> m/√<Hz> was comparable with the world best sensitivity obtained by TAMA300 gravitational wave detector. Its sensitivity was also enough to detect gravitational waves from compact binary star coalescences within 1 kpc from the Earth with S/N of 10. The stable operation, which was enabled by not only the lower seismic noise environment but also a newly installed self restart system, realized over 2000 hours observation in 2001 and the best operation rate of 99.8% in some selected 11 days. We also demonstrated the first coincidence gravitational wave observation from compact star (such as a MACHO black hole) binary inspiraling in our galaxy with TAMA300 in the summer of 2001. The data taken coincidentally totaled up to 709 hours. After selecting the gravitational waves candidates by using one step search, the coincident analysis checked arrival time, mass parameters and S/N ratio consistency. As a preliminary result, no gravitational wave signal was found. This result is expected to put a new upper limitation on gravitational wave search.