http://www.physorg.com/news114269153.html

"A lot of variety is possible, and it gets even more complicated because what's left behind at the end is still about 40 solar masses, and it continues to evolve and eventually makes an iron core and collapses, so you can end up with a gamma-ray burst. The possibilities are very exciting."

Supernova, supernova, supernova, supernova, (pause) BANG! black hole.

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"If this were play'd upon a stage now, I could condemn it as an improbable fiction."
Shakespeare, Twelfth Night
"The Mayan symbol for "book" looks a lot like a triple hamburger, but I've never seen them claiming it as proof the Mayans had Big Macs." - KaiYeves
"Distance doesn’t matter much in space, where if you just start a thing off with the right kind of shove, sooner or later it will get where you want it to go." -Frederik Pohl, Mining the Oort

Here is a better article:

http://physicsworld.com/cws/article/news/31801

It explains how such a star might have formed.

It also gives some idea of the time interval between the first two explosions.

Fortunate. Interesting. He's one of the very best, and always worth listening to closely. Like the little guy in the army helmet on "Laugh-in"....velly interesting. Pete.

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A third rate theory forbids.
A second rate theory explains after the fact.
A first rate theory predicts.
A. Lomonosov