Detection of High-Energy Gamma-Ray Emission during the X-ray flaring activity in GRB100728A

Abstract

We present the simultaneous Swift and Fermi observations of the bright GRB100728A and its afterglow. The early X-ray emission is dominated by a vigorous flaring activity continuing until 1 ks after the burst. In the same time interval high energy emission is significantly detected by the Fermi/LAT. Marginal evidence of GeV emission is observed up to later times. We discuss the broadband properties of this burst within both the internal and external shock scenarios, with a particular emphasis on the relation between X-ray flares, the GeV emission and a continued long-duration central engine activity as their power source.

accepted for publication in ApJ Letters. Contact authors: E. Troja, L. Piro, V. Vasileiou, S. Cutini, J. E. McEnery