Gamma-ray burst captured in unprecedented detail

This image shows 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. An international team led by University of Maryland astronomers has constructed a detailed description of a similar gamma-ray burst event, named GRB160625B. Their analysis has 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. Image credit: NASA’s Goddard Space Flight Center

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 including Liverpool John Moores University and led by 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 findings are published in the July 27, 2017 issue of the journal Nature.

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 suggests 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.

Professor Shiho Kobayashi, who is based at the LJMU Astrophysics Research Institute provided theoretical modeling and interpretation of the observational results.

“This study helps us to further understand the extreme environment of the Universe (strong gravity, relativistic shocks, and strong magnetic fields). Recent results from the Liverpool Telescope have backed up research that magnetic fields seem to play an essential role in the acceleration of jets, and so the Astrophysics Research Institute at LJMU is now continuing this work on time domain astronomy and understanding how relativistic jets jets often emerge from the neighbour of black holes.”

The research paper, “Significant and variable linear polarization during the prompt optical flash of GRB 160625B,” Eleonora Troja et al., was published in the journal Nature on July 27, 2017.