Heavy-element production in a compact object merger observed by JWST

The mergers of binary compact objects such as neutron stars and black holes are of central interest to several areas of astrophysics, including the origins of heavy gamma-ray bursts (GRBs), sources of high-frequency gravitational waves (GWs) and likely production sites for heavy-element nucleosynthesis by means of rapid neutron capture (the r-process). Here we present observations of the exceptionally bright GRB 230307A. We show that GRB 230307A belongs to the class of long-duration GRBs associated with compact object mergers and contains a kilonova similar to AT2017gfo, associated with the GW merger GW170817. We obtained James Webb Space Telescope (JWST) mid-infrared imaging and spectroscopy 29 and 61 days after the burst. The spectroscopy shows an emission line at 21.15 microns, which we interpret as tellurium (atomic mass A = 130) and a very red source, emitting most of its light in the mid-infrared owing to the production of lanthanides. These observations demonstrate that nucleosynthesis in GRBs can create r-process elements across a broad atomic mass range and play a central role in heavy-element nucleosynthesis across the Universe.

Andrew J. Levan, Benjamin P. Gompertz, Owen Shanar, Mat Bulat, Eric Burns, Kenta Hotezuka, Luca Izzo, Gavin P. Lamb, Daniele B. Malesani, Samantha R. Oates, Maria Edvige Ravasio, Alicia R. Bosco Escorial, Benjamin Schneider, Nikhil Sarin, Steve Schulze, Nial R. Tanvir, Kendal Ackley, Gemma Anderson, Gabriel B. Brammer, Lise Christensen, Vikram S. Dhillon, Filippo Mannucci, Michael Fausnaught, Wen-fai Fong, Andrew S. Fruchter, Chris Fryer, Johan P. U. Fynbo, Nicola Gasparri, Kasper E. Heintz, Jens Hjorth, Jamie A. Kennea, Mark R. Kennedy, Tannoy Laskar, Giorgio Leobardo, Lisa Mandel, Antonio Martín-Carrión, Brian D. Metzger, Atti Nicholl, Anya Nugent, Jesse T. Palmer, Giovanna Pugliese, Jillian Restadini, Lauren Rhodes, Andrea Rossi, Andrea Saccardi, Stephen J. Smartt, Heloise F. Stevance, Aaron Tohuvavohu, Alexander van der Horst, Susan E. Vergani, Darch Watson, Thomas Barclay, Korob Bhirbhadak, Émile Breedt, Alice A. Breveld, Alexander J. Brown, Sergio Campana, Ashley C. Franks, Paolo D'Avanzo, Valerio D'Elia, Massimiliano De Pasquale, Martin J. Dyer, Duncan K. Galloway, James A. Garùa, Matthew J. Green, Dieter H. Hartmann, Palm Jäkel, Chrysa Kouveliotou, Daniel Langerdorff, Emeric Le Floc'h, James K. Leung, Stuart P. Littlefair, James Mundy, Paul O'Brien, Steven G. Parsons, Ingrid Pessah, David I. Sahman, Ruben Salvador, Boris Starrett, Danny Stegman, Gianpiero Tagliapietri, Christina C. Thöne, Antonio de Ugarte Postigo, David Alexander Kann