Maria Grazia Bernardini, Raffaella Margutti, Jirong Mao, Elena Zaninoni, Guido Chincarini
We present the analysis of a large sample of Gamma-ray burst (GRB) X-ray
light curves in the rest frame to characterise their intrinsic properties in
the context of different theoretical scenarios. We determine the morphology,
time-scales and energetics of 64 long GRBs observed by Swift/XRT without
flaring activity. We furthermore provide a one-to-one comparison to the
properties of GRBs with X-ray flares. We find that the steep decay morphology
and its connection with X-ray flares favor a scenario in which a central engine
origin, as proposed by Kumar et al. (2008). We show that this scenario can
account also for the shallow decay phase, provided that the GRB progenitor star
has a self-similar structure with a constant envelope to core mass ratio $\sim
0.02-0.03$. However, difficulties arise for very long duration
($t_p\gtrsim10^4$ s) shallow phases. Alternatively, a spinning-down magnetar
whose emitted power refreshes the forward shock can quantitatively account for
the shallow decay properties. In particular we demonstrate that this model can
account for the plateau luminosity vs. end time anticorrelation found by
Dainotti et al. (2008, 2010).
View original:
http://arxiv.org/abs/1112.1058
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