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Speaker |
Mathews, Grant |
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Coauthors |
Remo Ruffini |
| Talk Title |
Constraining the Source for Gamma-ray bursts from X-Ray Afterglows |
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Abstract |
It has been pointed out the X-ray afterglows from long-duration GRBs are associated with energetic Type Ic supernovae and that they obey a universal scaling law. That is, the late time behavior of the afterglow from all GRBs follows the same universal normalization and power-law behavior at late times when plotted relative to the time of the initial GRB trigger. In this paper we describe constraints from this afterglow on the engine and surrounding medium for GRBs in the context of a model for X-ray emission from accelerated relativistic electrons within an outgoing relativistic shock. We show that such a universal scaling imposes 3 constraints: 1) The shock breakout energy is nearly the same for all bursts independently of when the shock becomes transparent and arrive at the power-law regime; 2) After breakout, the shock propagates through an optically thin low-density medium; and 3) The shock radiates adiabatically. We propose that these facts suggest that the late-time power-law afterglow emission derives from the underlying energetic supernova with a similar total shock energy. We also analyze the observed plateau region in the context of a model simple for the breakout of the supernova material shock heated by the GRB. We argue that the luminosity of the plateau suggests that:1) Dimmer GRBs correspond to the transport of the GRB shock through more material during breakout; and 2) All GRBs energize the outgoing shock to the same energy. We suggest that these points are most consistent with a GRB engine occurring at different radii within the expanding SN shell as in the induced gravitational collapse paradigm. |
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