Gamma-ray bursts are the most powerful things in the Universe, and scientists just found a long one coming from a kilonova.
The Vela satellites started detecting bursts of gamma radiation, but scientists soon realized that they weren’t coming from nuclear weapons or even from Earth. Eventually, scientists at the Los Alamos Scientific Laboratory determined the sky positions for 16 GRBs. Researchers publishedin the Astrophysical Journal in 1973 eliminating the Sun or the Earth as the sources for the GRBs, and the study of GRBs was born.
This artist’s impression shows two tiny but very dense neutron stars at the point at which they merge and explode as a kilonova. These events produce short gamma-ray bursts and gravitational waves. A new study shows that kilonovae can also produce long gamma-ray bursts like supernovae can. Image Credit: By University of Warwick/Mark Garlick, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=63436916,” and it’s published in the journal Nature. The lead author is Jillian Rastinejad, a Ph.
This illustration shows the setup for the most common type of gamma-ray burst. The core of a massive star has collapsed and formed a black hole. This “engine” drives a jet of particles that moves through the collapsing star and out into space at nearly the speed of light. The prompt emission typically lasts a minute or less. The afterglow emission occurs as the leading edge of the jet sweeps up its surroundings and emits radiation across the spectrum for months or even years.
But GRBs from a supernova emit an extraordinarily luminous afterglow. The team looked at the region that spawned the GRB with telescopes that can observe all across the electromagnetic spectrum. They watched for the telltale afterglow indicating that a supernova caused the GRB, and there was none. The team was starting to understand that they were seeing something new.
“This event looks unlike anything else we have seen before from a long gamma-ray burst,” said lead author Jillian Rastinejad. “Its gamma rays resemble those of bursts produced by the collapse of massive stars. Given that all other confirmed neutron star mergers we have observed have been accompanied by bursts lasting less than two seconds, we had every reason to expect this 50-second GRB was created by the collapse of a massive star.
“When we followed this long gamma-ray burst, we expected it would lead to evidence of a massive star collapse,” said Northwestern’s Wen-fai Fong, a senior author on the study. “Instead, what we found was very different. When I entered the field 15 years ago, it was set in stone that long gamma-ray bursts come from massive star collapses. This unexpected finding not only represents a major shift in our understanding but also excitingly opens up a new window for discovery.
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