Programme by Session

A new class of transient, the ultralong gamma-ray bursts (ULGRBs), was proposed following the Swift detection of three new transients active for thousands of seconds at gamma-ray energies and with afterglows as luminous as typical GRBs (e.g. Levan et al. 2014). Ideas to generate such long-lasting emission include the collapse of a larger progenitor star than those thought responsible for classical long GRBs, while other studies looked at mechanisms that could combine with a classical GRB scenario such as late-time energy injection from fall-back material.
The definition of a ULGRB must currently be restricted to its high energy characteristics, and the optical/UV light behaviour of the few candidates to date appears unrelated to the X-ray behaviour. Optical detection and monitoring, particularly during the extended prompt emission phase of ULGRBs is going to be a crucial element in revealing their energy generation mechanisms and constrain the progenitors. Only then will we be able to securely categorise the diverse range of GRB-like transients.