Gamma-Ray Burst Blasted 8th Century Earth
It’s pretty fascinating, the way things work. The discovery of elevated levels of carbon-14 in the rings of an ancient Japanese cedar tree can set off a chain of logical enquiry which leads to the conclusion that Earth was hit by a gamma ray burst 1200 years ago. Pretty amazing stuff…
(Read more at Discovery Space…)
Supernova Condensate 
The article rules out a solar flare because there were no significant aurorae, but that would only be if there was an associated geo-effective CME. There could still have been a huge X-ray flare, or flares, without aurorae surely?
A fair point… X-class flares are the most powerful variety, and do give out a significant amount of soft x-rays. However, while a flare and a CME are different processes, both eject a significant amount of charged particles which would caused increased aurorae.
Hambaryan & Neuhäuser do also mention that any such flare would have to be 20x what would be expected from the sun at the time. Admittedly, when writing articles like these, I do have to trust that the researchers involved got their calculations correct…
The research paper is free to read here – and it’s been accepted for formal publication, so it’s passed peer review too.