A Surprisingly short gamma-ray burst has prompted astronomers to reconsider what triggers these celestial cataclysms.
The Fermi gamma ray space telescope detected a one-second long gamma-ray burst, called GRB 200826A, in August 2020. These fleeting gamma-ray bursts, or GRBs, are believed to generally originate from breaking neutron stars. But a closer look at the outburst revealed that it came from the implosion of the core of a massive star.
In this scenario, the core of a star collapses into a compact object, such as a black hole, which propels high-speed jets of particles. Those jets pass through the rest of the star and radiate powerful gamma rays before the outer layers of the star explode in a supernova.. This process is generally believed to produce longer GRBs, lasting more than two seconds.
Discovering such a brief gamma-ray burst from a stellar explosion suggests that some bursts previously classified as stellar mergers may actually be from the death of massive stars, researchers report online July 26 in two studies in Nature Astronomy.
The first clues to the origin of GRB 200826A came from the pop itself. The wavelengths of the light and the amount of energy released in the burst were more similar to collapse-related GRBs than the bursts produced by collisions, report Bing Zhang, an astrophysicist at the University of Nevada, Las Vegas, and colleagues. . Also, the outburst came from the center of a star-forming galaxy., where astronomers expect to find massive collapsed stars, but not neutron star mergers, which are generally found on the fringes of quiet galaxies.
Another group, led by astronomer Tomás Ahumada-Mena of the University of Maryland at College Park, searched for the supernova that is expected to follow a GRB produced by a collapsing star. Using the Gemini North Telescope in Hawaii to observe GRB 200826A’s host galaxy, the team was able to identify the telltale infrared light from the supernova. The outburst may have been so brief because its jets barely passed through the star’s surface before they died down and the star exploded, Ahumada-Mena says.