Possibility of Past Supernova Detection with ^<14>C(Proceedingsof the 17^<th> Symposium on Researches Using the Tandetron AMS System at Nagoya University in 2004)

It was suggested by Konstantinov and Kocharov that gamma ray emission from a supernova explosion produces detectable amount of ^C in atmosphere of the earth. According to the idea, Damon et al. measured the ^C content in tree rings from AD 998 to AD 1025 and detected Δ^C increase of about 6‰ in AD 1010, which corresponds to an appearance of SN1006 (the supernova explosion that occurred in AD 1006). If the Δ^C increase is really due to the gamma-ray emission by SN1006, the result must be important for the study of cosmic ray acceleration by supernova explosions. However, it is not clear if the Δ^C increase in AD 1010 is caused by SN1006, because Δ^C variation caused by solar activity is not considered. To test the possibility of solar activity, we extended the duration of measurement of tree ring samples. We have measured tree rings of Yaku cedar from AD 992 to AD 1028 and determined Δ^C with the precision of ±2.8‰ by the accelerator mass spectrometry (AMS). Our result agrees with Damon's within the measurement error. Comparison of the 5 years before AD 1011 with the 5 years after shows an average increase of 4.1±1.7‰, which is similar to that of Damon. However, we can see the cyclic feature in the variation, which is similar to the 11-year cycle variation by solar activity as to a cycle length and the amplitude. Therefore, most part of Δ^C increase in AD 1012 is considered to be the variation caused by solar activity. We plan the measurement intended for SN1054, which is a type II supernova. Kinetic energy of type II supernovae is evaluated to be larger than that of type I supernovae (ex : SN1006). So, SN1054 would be more detectable.
第17回名古屋大学タンデトロン加速器質量分析計シンポジウム平成16(2004)年度報告 Proceedings of the 17th symposiumon Researches Using the Tandetron AMS System at Nagoya University in 2004\ 日時:平成17 (2005)年1月24日(月)､25日(火) 会場:名古屋大学シンポジオン Date:January 24th and 25th, 2005 Place:Nagoya University Symposion Hall