The unusual gamma-ray burst GRB 101225A explained as a minor body falling onto a neutron star

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. The tidal disruption of a solar-mass star around a supermassive black hole has been extensively studied analytically 1 , 2 and numerically 3 . In these events, the star develops into an elongated banana-shaped structure. After completing an eccentric orbit, the bound debris falls into the black hole, forming an accretion disk and emitting radiation 4 , 5 , 6 . The same process may occur on planetary scales if a minor body passes too close to its star. In the Solar System, comets fall directly into our Sun 7 or onto planets 8 . If the star is a compact object, the minor body can become tidally disrupted. Indeed, one of the first mechanisms invoked to produce strong gamma-ray emission involved accretion of comets onto neutron stars in our Galaxy 9 . Here we report that the peculiarities of the ‘Christmas’ gamma-ray burst (GRB 101225A 10 ) can be explained by a tidal disruption event of a minor body around an isolated Galactic neutron star. This would indicate either that minor bodies can be captured by compact stellar remnants more frequently than occurs in the Solar System or that minor-body formation is relatively easy around millisecond radio pulsars. A peculiar supernova associated with a gamma-ray burst provides an alternative explanation 11 .