Presentation #101A.06 in the session GRB 221009a.
As the most energetic explosions in the Universe, Long-duration Gamma-ray Bursts (GRBs) provide a unique opportunity to explore physics at extreme energy scales that are otherwise impossible to investigate in Earth-bound laboratories. The radiation produced by the interaction of their ejecta with the environment contains clues to their progenitors and to the mechanisms responsible for producing and collimating their relativistic jets. Whereas this radiation has traditionally been interpreted in the framework of synchrotron radiation from relativistic shocks, the discovery of VHE gamma-rays from GRBs complicates this model.
The recent bright, nearby GRB 221009A provides an excellent opportunity to test our understanding of processes responsible for GRB afterglow radiation. Whereas the X-ray/optical afterglow of this event was not dissimilar from other energetic GRBs, our radio observations reveal unexpected and unusual spectral and temporal evolution. We present multi-frequency radio observations of GRB 221009A beginning ~ 1.3 days after the burst and spanning from ~ 1 to ~ 100 GHz. We combine these observations, together with multi-wavelength optical and X-ray data to investigate the properties of this remarkable explosion. We conclude with a discussion of the role of radio observations and modeling in GRB science, highlighting the current and future role of radio observations in the ongoing multi-messenger revolution in extragalactic time-domain astrophysics.