A unified picture for gamma-ray burst prompt and X-ray afterglow emissions.pdf
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Mon. Not. R. Astron. Soc. 000, 000–000 (0000) Printed 5 February 2008 (MN LATEX style file v2.2)
A unified picture for gamma-ray burst prompt and X-ray
afterglow emissions
P. Kumar,1 E. McMahon1, S. D. Barthelmy2, D. Burrows3, N. Gehrels2, M. Goad4,
J. Nousek3, and G. Tagliaferri5
1Department of Astronomy, University of Texas, Austin, TX 78712
2NASA, Goddard Space Flight Center, Greenbelt, Maryland 20771
3Department of Astronomy and Astrophysics, 525 Davey Lab, Pennsylvania State University, University Park, PA 16802
4Department of Physics and Astronomy, University of Leicester, Leicester LE 1 7RH, UK
5INAF-Osservatorio Astronomico di Brera, Via Bianchi 46, I-23807 Merate (LC), Italy
5 February 2008
ABSTRACT
Data from the Swift satellite has enabled us for the first time to provide a complete
picture of the gamma-ray burst emission mechanism and its relationship with the
early afterglow emissions. We show that gamma-ray photons for two bursts, 050126
050219A, for which we have carried out detailed analysis were produced as a result of
the synchrotron self-Compton process in the material ejected in the explosion when
it was heated to a mildly relativistic temperature at a distance from the center of ex-
plosion of order the deceleration radius. Both of these bursts exhibit rapidly declining
early X-ray afterglow lightcurves; this emission is from the same source that produced
the gamma-ray burst. The technique we exploit to determine this is very general and
makes no assumption about any particular model for gamma-ray generation except
that the basic radiation mechanism is some combination of synchrotron and inverse-
Compton processes in a relativistic outflow. For GRB 050219A we can rule out the
possibility that energy from the explosion is carried outward by magnetic fields, and
that the dissipation of this field produced the γ-ray burst.
Key words: gamma-rays: bursts — shock waves — hydrodynamic
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