File:Hurleyetal2005.jpg

An exceptionally bright flare from SGR 1806−20 and the origins of short-duration γ-ray bursts Hurley et al.

Time-averaged counts in the tail phase of the giant flare, compared with the ‘trapped fireball’ model. Zero corresponds to 77,280 s UT. The step plot shows the RHESSI gamma-ray detector data averaged over the 7.56-s rotation period of the neutron star. It is fitted by a simple model (smooth curve) that describes the emission from the cool surface of a magnetically confined plasma as it contracts and evaporates in a finite time. Inset, RHESSI gamma-ray detector light curve for the first ten cycles of the flare tail. The energy range is 20–100 keV. The first peak of the trapped fireball emission is evident on the falling edge of the hard spike at t = 30 s. A changing twopeaked pulse–interpulse structure is present.