Monday

Gamma-Ray Bursts (GRBs) are the brightest explosions in the Universe and are modelled theoretically using the standard fireball model and synchrotron emission. Under this framework, after the initial characteristic prompt γ-ray emission, the collimated ejecta collides with the circumburst medium to produce an afterglow. A variety of afterglow light curve properties are expected depending on the relative contributions of the reverse and forward shock.

Using the newest leading technology facilities for GRB rapid follow-up, including the largest fully autonomous robotic optical telescope 2-m Liverpool Telescope, we can obtain early-time multi-wavelength photometry and polarimetry of the afterglow. Polarimetric observations are key to infer the magnetic field structure of the emission region and distinguish between baryonic and magnetic jet models. The reverse shock is predicted to be highly magnetized with globally ordered fields advected from the central engine (Gomboc et al. 2009, Steele et al, 2009 and Mundell et al,. 2013), whilst the forward shock emission should be unpolarized as the magnetization is thought to be produced locally in shocks.

In this talk, I will summarise the current state of the art, what insight our observations give into the structure, the evolution and the role of magnetic fields in the outflow and look to future prospects.