CONSTRAINING GAMMA-RAY BURST EMISSION PHYSICS WITH EXTENSIVE EARLY-TIME, MULTIBAND FOLLOW-UP

Understanding the origin and diversity of emission processes responsible for\nGamma-ray Bursts (GRBs) remains a pressing challenge. While prompt and\ncontemporaneous panchromatic observations have the potential to test\npredictions of the internal-external shock model, extensive multiband imaging\nhas been conducted for only a few GRBs. We present rich, early-time, multiband\ndatasets for two \\swift\\ events, GRB 110205A and GRB 110213A. The former shows\noptical emission since the early stages of the prompt phase, followed by the\nsteep rising in flux up to ~1000s after the burst ($t^{-\\alpha}$ with\n$\\alpha=-6.13 \\pm 0.75$). We discuss this feature in the context of the\nreverse-shock scenario and interpret the following single power-law decay as\nbeing forward-shock dominated. Polarization measurements, obtained with the\nRINGO2 instrument mounted on the Liverpool Telescope, also provide hints on the\nnature of the emitting ejecta. The latter event, instead, displays a very\npeculiar optical to near-infrared lightcurve, with two achromatic peaks. In\nthis case, while the first peak is probably due to the onset of the afterglow,\nwe interpret the second peak to be produced by newly injected material,\nsignifying a late-time activity of the central engine.\n