Early photometric and spectroscopic observations of the extraordinarily bright INTEGRAL-detected GRB 221009A

Abstract

initially detected as an X-ray transient by was later revealed to have triggered the satellite about an hour earlier, marking it as a post-peak observation of the event's emission. This GRB distinguished itself as the brightest ever recorded, presenting an unparalleled opportunity to probe the complexities of GRB physics. The unprecedented brightness, however, challenged observation efforts, as it led to the saturation of several high-energy instruments. Our study seeks to investigate the nature of the and elucidate the environmental conditions conducive to these exceptionally powerful bursts. Moreover, we aim to understand the fundamental physics illuminated by the detection of teraelectronvolt (TeV) photons emitted by grb. We conducted detailed analyses of early photometric and spectroscopic observations that span from the trigger through to the initial days following the prompt emission phase in order to characterize afterglow, and we complemented these analyses with a comparative study. Our findings from analyzing data confirm as the most energetic event observed to date. Early optical observations during the prompt phase negate the presence of bright optical emissions with internal or external shock origins. Spectroscopic analyses enabled us to measure distance and line-of-sight properties. The afterglow's temporal and spectral analysis suggests prolonged activity of the central engine and a transition in the circumburst medium's density. Finally, we discuss the implications for fundamental physics of detecting photons as energetic as 18 TeV from grb. Early optical observations have proven invaluable for distinguishing between the potential origins of optical emissions in underscoring their utility in GRB physics studies. However, the rarity of such data underscores the need for dedicated telescopes capable of synchronous multiwavelength observations. Additionally, our analysis suggests that the host galaxies of TeV GRBs share commonalities with those of long and short GRBs. Expanding the sample of TeV GRBs could further solidify these findings.