The Unique Potential of SKA Radio Observations of Gamma - Ray Bursts

Radio observations with the Square Kilometer Array (SKA) provide the agility, sensitivity, and spectral coverage to trace the evolution of the size, shape and spectra of gamma-ray burst (GRB) remnants from the earliest moments on. In the first hours to days after the burst a major, and unique tool, will be provided through the study of dynamically evolving radio spectra, caused by diffractive and refractive scintillation in the local ISM. Simultaneous observations from optically thin to optically thick frequencies will provide strong constraints on any model for the GRB remnant. SKA will also allow for extremely rapid (within minutes, if not seconds) follow-up observations by electronic steering of the array. SKA observations have the sensitivity to detect GRB afterglows out to redshifts of 10 or greater. They therefore allow studies of the high redshift universe, and measure the massive star formation (and massive star death rate!) history of the universe, unbiased by optical obscuration. Wide field surveys may detect thousands of GRBs within a few days of observing (depending on the amount of collimation, the width of the GRB luminosity function, the number of GRBs like GRB 980425/SN 1998bw). There would be new ones, but many more would be old, fading afterglows, allowing the determination of the multi-variate GRB-optical-radio luminosity function of GRBs. This should elucidate the relation of the 'faint' ones, like GRB 980425, to the luminous ones like GRB 970508. Such surveys will also tell us whether GRB fireballs (and which ones) are collimated into jets.