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28th of July 2017
Gamma-ray Burst Captured in Unprecedented Detail
by Troja et al.
Gamma-ray bursts are among the most energetic and explosive events in the universe. They are also short-lived, lasting from a few milliseconds to about a minute. This has made it tough for astronomers to observe a gamma-ray burst in detail. Using a wide array of ground- and space-based telescope observations, an international team led by Eleonora Troja (University of Maryland) constructed one of the most detailed descriptions of a gamma-ray burst to date. The event, named GRB160625B, revealed key details about the initial "prompt" phase of gamma-ray bursts and the evolution of the large jets of matter and energy that form as a result of the burst.

The group's observations provide the first answers to some long-standing questions about how a gamma-ray burst evolves as the dying star collapses to become a black hole. First, the data suggest that the black hole produces a strong magnetic field that initially dominates the energy emission jets. Then, as the magnetic field breaks down, matter takes over and begins to dominate the jets. Most gamma-ray burst researchers thought that the jets were dominated by either matter or the magnetic field, but not both. The current results suggest that both factors play key roles.

Radio observations played an important role in understanding the explosion properties, the jet structure, and determining the nature of the very bright, early optical emission. Although the main result comes from the early optical/gamma-ray data, it would not have been possible to obtain a robust result without the efforts of many facilities, including a significant contribution from CSIRO's Australia Telescope Compact Array.

The image above shows an artist's impression of the most common type of gamma-ray burst, thought to occur when a massive star collapses, forms a black hole, and blasts particle jets outward at nearly the speed of light. The results of this work are described in this week's issue of Nature.

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