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Letter to the Editor
GRB afterglows: from ultra-relativistic to non-relativistic phase
Received 15 June 1998 / Accepted 6 July 1998
Postburst evolution of adiabatic fireballs that produce -ray bursts is studied. Emphasis has been put on the transition from the highly relativistic phase to the non-relativistic phase, which, according to our calculation, should happen much earlier than previously expected. The theoretical light curves decline a little sharper at the non-relativistic stage than at early times, but still can fit the observations well. However, disagreements are obvious when d, implying a large initial energy , a low interstellar density n, or the possible existence of a persistent energy source at the center of the fireball.
Key words: gamma rays: bursts shock waves stars: neutron ISM: jets and outflows relativity
Send offprint requests to: T. Lu (e-mail: firstname.lastname@example.org)
Online publication: July 27, 1998