RESUMO
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)1, sources of high-frequency gravitational waves (GWs)2 and likely production sites for heavy-element nucleosynthesis by means of rapid neutron capture (the r-process)3. 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 mergers4-6 and contains a kilonova similar to AT2017gfo, associated with the GW merger GW170817 (refs. 7-12). 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 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.
RESUMO
Complete samples are the basis of any population study. To this end, we selected a complete subsample of Swift long bright gamma ray bursts (GRBs). The sample, made up of 58 bursts, was selected by considering bursts with favourable observing conditions for ground-based follow-up observations and with the 15-150 keV 1 s peak flux above a flux threshold of 2.6 photons cm(-2) s(-1). This sample has a redshift completeness level higher than 90 per cent. Using this complete sample, we investigate the properties of long GRBs and their evolution with cosmic time, focusing in particular on the GRB luminosity function, the prompt emission spectral-energy correlations and the nature of dark bursts.