Astronomers witness heavy elements emerge after bright gamma-ray burst

An international team of astronomers including Radboud astronomers Ashley Chrimes, Nicola Gaspari, Andrew Levan, Daniele Bjorn Malesani and Maria Ravasio has discovered heavy elements in the wake of a bright gamma-ray burst in a galaxy about 1 billion light-years away. The burst occurred on March 7, 2023, when two neutron stars merged to form a so-called kilonova. It is the first kilonova whose aftermath was observed using the James Webb Space Telescope. The researchers publish their findings in the journal Nature.

The gamma-ray burst, GRB230307A, is the second brightest burst in the 50 years since the search for gamma-ray bursts began. GRB230307A is a thousand times brighter than the typical gamma-ray burst. The burst lasted a long time, about 200 seconds. ’ This is a long, and extremely bright burst, something we only expect once every few decades,’ said team member Daniele Bjorn Malesani. 

Further investigation with multiple telescopes on Earth and in space revealed that the burst originated from a  kilonova. The kilonova occurred when two neutron stars merged in a galaxy 1 billion light-years from Earth.

"There are only a mere handful of known kilonovas, and this is the first time we have been able to look at the aftermath of a kilonova with the  James Webb Space Telescope ," said research leader  Andrew Levan (Radboud University, the Netherlands). He was also involved in the first detection of a kilonova back in 2013.

Thanks to the Near-Infrared Spectrograph of the James Webb Space Telescope, developed partly in the Netherlands, the researchers saw peaks in the infrared spectrum of the kilonova that correspond to the typical fingerprint of the element  tellurium. The astronomers also observed hints of  rare earth elements.

’We used to look for kilonovae following gravitational waves, but discovering them also in connection with long gamma-ray bursts provides a novel way to find these explosions, and to better where the heavy elements in the Universe are produced,’ said Maria Ravsio, a co-author of the paper, also at Radboud University. In the future, the researchers hope to do combined observations of kilonovas more often. This will allow them to solidify the theory about the formation of heavy elements in kilonovas.