An Extra Long X-Ray Plateau in a Gamma-Ray Burst and the Spinar Paradigm.pdf

a r X i v : 0 7 0 5 .1 6 4 8 v 4 [ a s t r o - p h ] 7 S e p 2 0 0 7 An Extra Long X-Ray Plateau in a Gamma-Ray Burst and the Spinar Paradigm V.Lipunov1,2,3 E.Gorbovskoy1,2,3 ABSTRACT The recently discovered gamma-ray burst GRB 070110 displayed an extraor- dinary X-ray afterglow with Xray radiation—i.e., an X-ray plateau—observed for 20,000 s. We show that the observed properties of the plateau can be naturally interpreted in terms of the model with a spinar—a quasi—equilibrium collapsing object whose equilibrium is maintained by the balance of centrifugal and grav- itational forces and whose evolution is determined by its magnetic field. If this model is true, then for 1 hr, the Swift X-ray telescopes recorded radiation from an object with a size smaller than the Schwarzschild radius! Subject headings: Gamma-ray burst, Black holes, magnetic field, rotation 1. Introduction After three years of the operation of Swift space observatory (Gehrels, N., et al, 2004) it becomes evident that the temporal behavior of many gamma-ray bursts exhibits such features as delayed flares (Chincarini, G., et al., 2007) and early precursors (Lazzati, 2005), which can in no way be reconciled with the instantaneous point explosion model and which are indicative of a long (compared to the duration of the gamma-ray burst) time of operation of the central engine (Gehrels, N., et al, 2006; Wang Meszaros, 2007). The recently discovered gamma-ray burst GRB 070110 displayed an extraordinary x- ray afterglow with x-ray radiation — x-ray plateau — observed for 20 000 seconds (Troja, E., et al. 2007).The gamma-ray burst GRB 050904 exhibits a similar behavior (Cusumano et al., 2006). Such a behavior demonstrates the central engine long-activity and gives an insight into the mechanisms of its operation. We show that the observed properties of the 1Moscow State University 2 Sternberg Astronomical Institute 3Moscow Union “Optic” – 2 – plateau can be naturally interpreted in terms of a spinar