Orateur
Description
Gamma-ray bursts (GRBs) are typically observed as brief flashes of MeV radiation. Short-duration GRBs (< 2 s) are commonly associated with neutron star mergers, making them prime multi-messenger sources with gravitational waves. Long-duration GRBs (~20 s), on the other hand, are linked to certain classes of collapsars. Despite this broad dichotomy, recent discoveries have revealed puzzling cases. GRB 211211A and GRB 230307A are long-duration events (> 30 s) that nonetheless show clear kilonova signatures. I will discuss the distinctive features of these “oddballs” in comparison with historical long GRBs.
A further subclass is the ultra-long GRBs. I will present the properties of the recently detected GRB 250702D/B/E, which persisted for more than three hours. Its MeV emission, followed by a rapid X-ray decline, suggests an origin in a relativistic jet powered by the tidal disruption of a star by an intermediate-mass black hole. Although rare, such tidal disruption events are compelling as potential sources of low-frequency gravitational waves.
