"This discovery dramatically moves back the time at which we know short GRBs were exploding. The short burst is almost twice as far as the previous confirmed record holder," says John Graham of the Johns Hopkins University, in Baltimore, Md.

GRBs are among the most powerful explosions in the universe, releasing enormous amounts of energy in the form of X-rays and gamma rays. Most bursts fall in one of two categories: long bursts and short bursts, depending on whether they last longer or shorter than three seconds. Astronomers think that long GRBs are triggered by the collapse and explosion of massive stars. In contrast, a variety of mechanisms have been proposed for short bursts. The most popular model says that most short GRBs occur when two neutron stars smash into each other and collapse into a black hole, ejecting energy in two counterflowing beams.

The record-setting short burst is known as GRB 070714B, since it was the second GRB detected on July 14, 2007. Swift discovered the GRB in the constellation Taurus. The burst’s high energy and 3-second duration firmly place it in the short GRB category. Rapid follow-up observations with the 2-meter Liverpool Telescope and the 4-meter William Herschel Telescope found an optical afterglow in the same location as the burst, which allowed astronomers to identify the GRB’s host galaxy.

 Source : Science Daily