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Abstract GRB 221009A is one of the brightest transients ever observed, with the highest peak gamma-ray flux for a gamma-ray burst (GRB). A Type Ic-BL supernova (SN), SN 2022xiw, was definitively detected in late-time JWST spectroscopy (t= 195 days, observer frame). However, photometric studies have found SN 2022xiw to be less luminous (10%−70%) than the canonical GRB-SN, SN 1998bw. We present late-time Hubble Space Telescope (HST)/WFC3 and JWST/NIRCam imaging of the afterglow and host galaxy of GRB 221009A att∼185, 277, and 345 days post-trigger. Our joint archival ground, HST, and JWST light-curve fits show strong support for a break in the light-curve decay slope att= 50 ± 10 days (observer frame) and a SN at <1.5× the optical/near-IR flux of SN 1998bw. This break is consistent with an interpretation as a jet break when requiring slow-cooling electrons in a wind medium with an electron energy spectral indexp> 2 andνm<νc. Our light curves and joint HST/JWST spectral energy distribution (SED) also show evidence for the late-time emergence of a bluer component in addition to the fading afterglow and SN. We find consistency with the interpretations that this source is either a young, massive, low-metallicity star cluster or a scattered-light echo of the afterglow with a SED shape offν∝ν2.0±1.0.
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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 H2emission at the explosion site, which is consistent with recent star formation, hinting that environmental factors are responsible for its extreme energetics.
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- PAR ID:
- 10500235
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Publisher / Repository:
- Nature Publishing Group
- Date Published:
- Journal Name:
- Nature Astronomy
- Volume:
- 8
- Issue:
- 6
- ISSN:
- 2397-3366
- Format(s):
- Medium: X Size: p. 774-785
- Size(s):
- p. 774-785
- Sponsoring Org:
- National Science Foundation
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