AGILE and Konus-Wind Observations of GRB 190114C: The Remarkable Prompt and Early Afterglow Phases

39siGRB 190114C represents a breakthrough for the physics of gamma-ray bursts (GRBs), being the first GRB with delayed emission above 300 GeV, as reported by MAGIC. We present in this paper the sub-MeV/MeV data of the prompt and early afterglow emissions of GRB 190114C, as detected by AGILE and Konus-Wind, in the 20 keV-100 MeV energy range. The first stages of the burst exhibit multiple emission components, associated with an interesting spectral evolution. The first 2 s of the prompt emission can be described by a single "Band-like"spectral component. The successive 4 s show the presence of an additional high-energy spectral component, which quickly evolves into a "hard-flat"component of the νF ν spectrum, extending up to 10-100 MeV and likely produced by inverse Compton radiation, whose onset and evolution are clearly shown in our data. After this phase, the νF ν spectrum evolves into a "V shape,"showing the persistence and spectral hardening of the additional high-energy component in substantial agreement with Fermi and Swift results. We also analyze the first ∼200 s of the early afterglow that show a reflaring episode near T 0 + 15 s. We identify a new, so-far-unnoticed flux temporal break near T 0 + 100 s, which is detected in hard X-rays by both Konus-Wind and INTEGRAL/SPI-ACS. We find this break incompatible with the commonly assumed adiabatic evolution of a fireball in a constant-density medium. We interpret this break as a consequence of radiative evolution of the early afterglow from a fireball expanding in a wind-like circumburst medium.nonemixedUrsi A.; Tavani M.; Frederiks D.D.; Romani M.; Verrecchia F.; Marisaldi M.; Aptekar R.L.; Antonelli L.A.; Argan A.; Bulgarelli A.; Barbiellini G.; Caraveo P.; Cardillo M.; Casentini C.; Cattaneo P.W.; Chen A.; Costa E.; Donnarumma I.; Evangelista Y.; Feroci M.; Ferrari A.; Fuschino F.; Galli M.; Giuliani A.; Labanti C.; Lazzarotto F.; Longo F.; Lucarelli F.; Morselli A.; Paoletti F.; Parmiggiani N.; Piano G.; Pilia M.; Pittori C.; Svinkin D.S.; Trois A.; Tsvetkova A.E.; Vercellone S.; Vittorini V.Ursi, A.; Tavani, M.; Frederiks, D. D.; Romani, M.; Verrecchia, F.; Marisaldi, M.; Aptekar, R. L.; Antonelli, L. A.; Argan, A.; Bulgarelli, A.; Barbiellini, G.; Caraveo, P.; Cardillo, M.; Casentini, C.; Cattaneo, P. W.; Chen, A.; Costa, E.; Donnarumma, I.; Evangelista, Y.; Feroci, M.; Ferrari, A.; Fuschino, F.; Galli, M.; Giuliani, A.; Labanti, C.; Lazzarotto, F.; Longo, F.; Lucarelli, F.; Morselli, A.; Paoletti, F.; Parmiggiani, N.; Piano, G.; Pilia, M.; Pittori, C.; Svinkin, D. S.; Trois, A.; Tsvetkova, A. E.; Vercellone, S.; Vittorini, V