JWST detection of heavy neutron capture elements in a compact object merger

TL;DR

This paper reports JWST observations of a gamma-ray burst associated with a neutron star merger, revealing evidence of heavy element nucleosynthesis, including tellurium and lanthanides, confirming the role of such mergers in creating r-process elements.

Contribution

First JWST mid-IR observations of a neutron star merger's kilonova, detecting heavy r-process elements like tellurium and lanthanides, confirming their synthesis in GRBs.

Findings

Detection of tellurium emission line at 2.15 microns

Observation of a very red, mid-IR emitting kilonova

Evidence that GRBs contribute to heavy element nucleosynthesis

Abstract

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), sources of high-frequency gravitational waves and likely production sites for heavy element nucleosynthesis via rapid neutron capture (the r-process). These heavy elements include some of great geophysical, biological and cultural importance, such as thorium, iodine and gold. Here we present observations of the exceptionally bright gamma-ray burst GRB 230307A. We show that GRB 230307A belongs to the class of long-duration gamma-ray bursts associated with compact object mergers, and contains a kilonova similar to AT2017gfo, associated with the gravitational-wave merger GW170817. We obtained James Webb Space Telescope mid-infrared (mid-IR) 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 A=130), and a very red source, emitting most of its light in the mid-IR due 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.