Two views of Christmas γ-ray burst

The Christmas γ-ray burst of 25 December 2010 (GRB 101225A, first detected by the Swift orbiting observatory) was a very unusual event. It was long lasting without the typical decreasing trend, its X-ray afterglow faded rapidly and its spectrum was atypical. Two papers in this issue offer very different explanations for these puzzling properties. Sergio Campana's group favours a comet crashing onto a neutron star as the cause of the outburst. Christina Thöne's group prefers a more conventional supernova mechanism, in this case involving a merger between a helium star and a neutron star.