Gravitational waves from an SMBH binary in M87

In this paper, we study gravitational-wave (GW) emission from a hypothetical supermassive black-hole (SMBH) binary at the center of M87. The existence of a SMBH other than that usually identified with the central AGN is a possible explanation for the observed displacement ($\sim O(1)~{\rm pc}$) between the AGN and the galactic centroid, and it is reasonable to assume consid- ering the evolution of SMBHs through galaxy mergers. Because the period of the binary and the resulting GWs is much longer than the observational time span, we calculate the variation of the GW amplitude, rather than the amplitude itself. We investigate the dependence on the orbital elements and the second BH mass taking the observational constraints into account. The frequency of the GWs is too low to be detected with the conventional pulsar timing array and we propose a new method to detect such low-frequency GWs with the distribution func- tion of pulsar spin-down rates. Although the GWs from a SMBH binary which explains the observed displacement is extremely hard to be detected even with the new method, GWs are still a useful way to probe the M87 center.Comment: 5 pages, 6 figures. Accepted for Publications of the Astronomical Society of Japa

岡山県立大学2016年入学生の英語学習に対する認識

This study looks at changing perceptions of English-language education and e-learning among first-year students at Okayama Prefectural University (OPU) after completing a full year of English classes. We conducted a questionnaire-based survey at the beginning and end of the 2016 academic year, and the results show that although students had similar beliefs about learning English, their desire to learn English had decreased by the end of the year. Furthermore, while only slightly less than half of students felt that the materials were effective, more than half did not like using them.本稿は、岡山県立大学2016年度に入学した学生を対象として、大学入学当初と2016年度末に学習者ビリーフ（学習に対する態度・不安・願望）を調査した報告である。主な結果として、多くの学習者が、１年次における英語学習を終えた後、英語学習に対する意欲を低下させていることが明らかになった。また、e-learning学習は効果的であると認めながらも、好きではないと回答した学生が多かった。教師は、学生の英語学習に対するニーズが何であるのかを常に意識していかなければいけないことが示唆された