JWST detection of a supernova associated with GRB 221009A without an r-process signature

Abstract

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.

GRB 221009A/SN 2022xiw: A Supernova Obscured by a Gamma-Ray Burst Afterglow?

“…We therefore tried to describe the multiband light curves with a single-decline-rate power law, f (t) ∝ t −1.56 ; the result is shown in Figure 1, where one can see that in all bands, there is no significant bump signature. Table 3 compares the parameters with the results reported by other works (Fulton et al 2023;Srinivasaragavan et al 2023;Blanchard et al 2024) and the general value of GRB-SNe (Cano et al 2017). Our results are close to those of Srinivasaragavan et al (2023) and consistent with the average value inferred by Cano et al (2017) for other GRB-SNe except for the expansion velocity of the ejecta, v ej .…”

“…The close match with SNe Ic-BL in particular demonstrates the presence of a typical GRB-SN in the spectrum. These observations provide the first clear detection of an SN associated with GRB 221009A (Blanchard et al 2024). Moreover, Srinivasaragavan et al (2023) also announced that they found moderate evidence for the presence of an additional component arising from an associated SN and found that it must be substantially fainter than SN 1998bw (see more details in the review by Srinivasaragavan et al 2023).…”

“…But late-time JWST observations possibly suggest some specific SN spectral features associated with GRB 221009A. In particular, a close match with SNe Ic-BL suggests the presence of a typical GRB-SN in the spectrum (Blanchard et al 2023(Blanchard et al , 2024.…”

Fitting the Crab Supernova with a Gamma-Ray Burst

“…The connections between GRBs and Supernovae have been documented several times. The cosmological distances of GRBs made the observations of the related SN very difficult because they can be immersed in the GRB optical afterglow, but some well-documented cases exist [16].…”

Fitting the Crab Supernova with a Gamma-Ray Burst

“…The connections between GRB and Supernovae have been documented several times. The cosmological distances of GRB made the observations of the related SN every difficult, because they can be immersed in the GRB optical afterglow, but some well documented cases exist [17].…”