Speaker
Description
GRB 221009A is the brightest gamma-ray burst ever detected by the Swift Observatory, with the highest peak gamma-ray flux for a GRB. It was detected once by the Burst Alert Telescope (BAT) during the prompt emission and again during the high-energy afterglow phase–a feat matched by no other GRB. Early data (t < 60 d) has shown a complicated picture with several projects finding a wide range of flux limits for the associated supernova (10–70% x SN 1998bw), theory-defying synchrotron physics for the afterglow, and breaks in the optical light curves and decay slopes leading to possible jet break times of 45 min to > 100 days after trigger. In this talk, I present late-time Hubble Space Telescope (HST)/WFC3 and JWST/NIRCam imaging of the afterglow and host galaxy of GRB 221009A at t ~ 185, 277, and 345 days post-trigger. The joint archival ground, HST, and JWST light curve fits show strong support for a break in the light curve decay slope at t = 50 +/- 10 days (observer-frame) and a supernova at 1.4+0.37−0.40× the optical/NIR 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 the electron energy spectral index, p > 2, and ν_m < ν_c. The light curve 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 supernova. 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.
