摘要
According to analysis of the ^14C content in two Japanese trees, that grew over a period of approximately 3000 years, with high time resolution, Miyake et al. found a rapid increase at AD 774-775 and another one at AD 993-994. These increases correspond to high-energy events that happened within those years and radi- ated ＂）,-ray energy of about 7x 1034 erg toward the Earth. The origin of these events is a mystery. Such strong events should have an unusual optical counterpart, and have been recorded in historical literatures. We searched Chinese historical materi- als around AD 744-775 and AD 993-994, but no remarkable event was found except for a violent thunderstorm in AD 775. However, the possibility of a thunderstorm containing so much energy is unlikely. We conclude that the events, which caused the 14C increase, are still unclear. These events most probably had no optical counterpart, and a short gamma-ray burst, giant flare of a soft gamma-ray repeater or a terrestrial γ-ray flash could all be candidates.
According to analysis of the ^14C content in two Japanese trees, that grew over a period of approximately 3000 years, with high time resolution, Miyake et al. found a rapid increase at AD 774-775 and another one at AD 993-994. These increases correspond to high-energy events that happened within those years and radi- ated ＂）,-ray energy of about 7x 1034 erg toward the Earth. The origin of these events is a mystery. Such strong events should have an unusual optical counterpart, and have been recorded in historical literatures. We searched Chinese historical materi- als around AD 744-775 and AD 993-994, but no remarkable event was found except for a violent thunderstorm in AD 775. However, the possibility of a thunderstorm containing so much energy is unlikely. We conclude that the events, which caused the 14C increase, are still unclear. These events most probably had no optical counterpart, and a short gamma-ray burst, giant flare of a soft gamma-ray repeater or a terrestrial γ-ray flash could all be candidates.
基金
supported by the National Natural Science Foundation of China (Grant No. U1231101)
the National Basic Research Program of China (973 Program, Grant No. 2014CB845800)
