Burst Remnants : How can we find them ?

By now there is substantial evidence that Gamma-Ray Bursts (GRBs) originate at cosmological distances from very powerful explosions. The interaction between a GRB and its surrounding environment has dramatic consequences on the environment itself. At early times, the strong X-ray UV afterglow flux photoionizes the medium on distance scales on the order of 100 pc [7], destroys dust [10], creates photoionization edges [6]. These are short-term effects, that occur while the afterglow is propagating into the medium. In this contribution, I discuss the long-term effects resulting from the interaction between a GRB and its environment. In particular, in §2, I discuss signatures of the emission spectrum produced while the heated and ionized gas slowly cools and recombines. Besides photoionizing the medium with its afterglow, a GRB explosion drives a blast wave which is expected to have a very long lifetime. In §3, I discuss possible candidates for such GRB remnants in our own and in nearby galaxies, and ways to distinguish them from remnants due to other phenomena, such as multiple supernova (SN) explosions.