On December 11, 2021, NASA’s Fermi Gamma-ray Space Telescope and Neil Gehrels’ Swift Observatory discovered a burst of high-energy light coming from the edge of a galaxy about a billion miles away. light years away. The occurrence has challenged scientists’ perceptions of gamma-ray bursts (GRBs), the most powerful phenomena in the cosmos.
The burst GRB 211211A was the first long-duration gamma-ray burst traced to a merging neutron star origin. Considered a paradigm shift, the outburst lasted about a minute and our follow-up observations led to the identification of a kilonova.
Eleonora Troja, an astrophysicist at the University of Rome who led another team that studied the explosion, said: “Many years ago, Neil Gehrels, an astrophysicist and Swift’s namesake, suggested that neutron star mergers could produce some long bursts. The kilonova we observed is evidence that connects mergers to these long-duration events, forcing us to rethink how black holes form.”
Alessio Mei, a PhD student at the Gran Sasso Science Institute in L’Aquila, Italy, who led a group that studied the data, said: “This is the first time we have seen an excess of high-energy gamma rays in the glow of a merger event. This emission usually diminishes with time. It is possible that these high-energy gamma rays come from collisions between the visible light of the kilonova and the electrons in the particle jets. The jets they could be weakening due to the original explosion or new ones powered by the resulting black hole or magnetar.”
Scientists believe that the heavy elements in the cosmos have been produced by neutron star mergers. They based their calculations on the frequency of short bursts believed to occur in the cosmos. Now they will also have to take extended bursts into account in their calculations.
Regina Caputo, Swift project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, said, “This result underscores the importance of our missions working together and with each other to provide multi-wavelength tracking these kinds of phenomena. Similar coordinated efforts have hinted that some supernovae might produce short bursts, but this event is the final nail in the coffin of the simple dichotomy we’ve used for years. You never know when you might find something surprising.”
Journal references:
- Rastinejad, JC, Gompertz, BP, Levan, AJ et al. A kilonova after a long-duration gamma-ray burst at 350 Mpc. Nature 612, 223–227 (2022). DOI: 10.1038/s41586-022-05390-w
- Troja, E., Fryer, CL, O’Connor, B., et al. A long burst of nearby gamma rays from a merger of compact objects. Nature 612, 228–231 (2022). DOI: 10.1038/s41586-022-05327-3
- Mei, A., Banerjee, B., Oganesyan, G. et al. Gigaelectronvolt emission from a compact binary merger. Nature 612, 236–239 (2022). DOI: 10.1038/s41586-022-05404-7
- Gompertz, BP, Ravasio, ME, Nicholl, M. et al. The case of a minute-long fusion-driven gamma-ray burst by rapidly cooling synchrotron emission. Nat Astron (2022). DOI: 10.1038/s41550-022-01819-4