The Fermi Gamma-ray Space Telescope has been observing high-energy emission from gamma-ray bursts for over ten years. These events signal the death of a massive star, or the merger of two neutron stars - extremely dense stellar remnants. In both cases, a black hole may be created and vast amounts of energy are released. The results from the Fermi observations give researchers new insight into the physical processes at work. One of the lead authors of a the newly published 10-year catalog is Magnus Axelsson, an astrophysicist at the Department of Astronomy, Stockholm University in Sweden.


“Each burst is in some way unique,” he says. “It’s only when we can study large samples, as in this catalog, that we begin to understand the common features of GRBs. These in turn give us clues to the physical mechanisms at work.”


Observing a gamma-ray burst takes speed and luck - they can appear anywhere on the sky and most of them fade within minutes. That’s why telescopes such as Fermi, with a large field of view, are required. The satellite orbits the Earth once every 90 minutes, and observes about 20% of the sky at any given time. 


The study has focused on the gamma-ray bursts which emit the most energetic photons, millions of times more than visible light. On average roughly one gamma-ray burst per day occurs somewhere on the sky, but very few reach these big energies. Fermi also carries

a smaller instrument which observes X-rays. During the ten years of the study, this could find over 2300 gamma-ray bursts, but only 186 reached high enough energies to be included in the catalog. 


“The results are still a large step forward,” says Magnus Axelsson. “An earlier catalog, made after three years, contained only 35 events. Thanks to improved analysis techniques we’re getting better at identifying high-energy emission from gamma-ray bursts. This allows us to challenge theoretical models, and leads to new discoveries and even more questions."


Read more about the study, and see examples of record-setting and intriguing events from the catalog that have helped scientists learn more about gamma-ray bursts, in the full NASA press release!


Paper in the Astrophysical Journal.