"this is a really, really unusual event," study co-author joshua bloom, assistant professor of astronomy at university of california, berkeley, told space.com. "it's now about two-and-a-half months old, and the fact that it just continues on and is only fading very slowly is the one really big piece of evidence that tells us this is not an ordinary gamma-ray burst."
"a rare sight that astronomers say likely happens only once every 100 million years"
what i especially like about this particular phenomenon is summed up in a sentence in the (separate) wiki article on this particular grb (110328a):
"the beam of radiation appears to be pointed directly toward earth."
or, as it's summed up at space.com:
astronomers were even luckier to have been able to witness the event with such detail and clarity, since the jet of x-rays and high-energy gamma rays were punched out along a rotation axis that placed earth in the eye of the beam. "this is part of the special nature of the event," bloom said. "what we have is a geometrical rarity on top of an already rare event. i would be surprised if we saw another one of these anywhere in the sky in the next decade."
the astronomers suspect that the gamma-ray emissions began on march 24 or 25, at a distance of about 3.8 billion light-years away. and while they are still detecting activity from this event, bloom and his colleagues estimate that the emissions will fade over the next year.
oh, and the picture of grb 110328a at the wiki article is courtesy of hubble, cuz hubble got you.