My GRB hypothesis was that it was the result of excessive turtle flatulence, from all those turtles on whose backs the Universe is stacked.
A classic example of meglomania -- projecting your own deficiencies onto the entire universe.
Here's a link to desciption of the multiple mirror x-ray system. (No mention of the turtles)
XMM instruments described here
Interesting combination of spectrometry and hi resolution. ... with an optical & UV system to boot.