- Blanchard, Peter;
- Villar, V;
- Chornock, Ryan;
- Laskar, Tanmoy;
- Li, Yijia;
- Leja, Joel;
- Pierel, Justin;
- Berger, Edo;
- Margutti, Raffaella;
- Alexander, Kate;
- Barnes, Jennifer;
- Cendes, Yvette;
- Eftekhari, Tarraneh;
- Kasen, Daniel;
- LeBaron, Natalie;
- Metzger, Brian;
- Muzerolle Page, James;
- Rest, Armin;
- Sears, Huei;
- Siegel, Daniel;
- Yadavalli, S
Identifying the sites of r-process nucleosynthesis, a primary mechanism of heavy element production, is a key goal of astrophysics. The discovery of the brightest gamma-ray burst (GRB) to date, GRB 221009A, presented an opportunity to spectroscopically test the idea that r-process elements are produced following the collapse of rapidly rotating massive stars. Here we present James Webb Space Telescope observations of GRB 221009A obtained +168 and +170 rest-frame days after the gamma-ray trigger, and demonstrate that they are well described by a SN 1998bw-like supernova (SN) and power-law afterglow, with no evidence for a component from r-process emission. The SN, with a nickel mass of approximately 0.09 M ⊙, is only slightly fainter than the brightness of SN 1998bw at this phase, which indicates that the SN is not an unusual GRB-SN. This demonstrates that the GRB and SN mechanisms are decoupled and that highly energetic GRBs are not likely to produce significant quantities of r-process material, which leaves open the question of whether explosions of massive stars are key sources of r-process elements. Moreover, the host galaxy of GRB 221009A has a very low metallicity of approximately 0.12 Z ⊙ and strong H2 emission at the explosion site, which is consistent with recent star formation, hinting that environmental factors are responsible for its extreme energetics.