Heavy-element production in a compact object merger observed by JWST
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Abstract
<jats:title>Abstract</jats:title> <jats:p> The mergers of binary compact objects such as neutron stars and black holes are of central interest to several areas of astrophysics, including as the progenitors of gamma-ray bursts (GRBs) <jats:sup>1</jats:sup> , sources of high-frequency gravitational waves (GWs) <jats:sup>2</jats:sup> and likely production sites for heavy-element nucleosynthesis by means of rapid neutron capture (the <jats:italic>r</jats:italic> -process) <jats:sup>3</jats:sup> . 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 <jats:sup>4–6</jats:sup> and contains a kilonova similar to AT2017gfo, associated with the GW merger GW170817 (refs. <jats:sup>7–12</jats:sup> ). 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 2.15 microns, which we interpret as tellurium (atomic mass <jats:italic>A</jats:italic> = 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 <jats:italic>r</jats:italic> -process elements across a broad atomic mass range and play a central role in heavy-element nucleosynthesis across the Universe. </jats:p>