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Astron. Astrophys. 336, L69-L72 (1998)


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Letter to the Editor

GRB afterglows: from ultra-relativistic to non-relativistic phase

Y.F. Huang 1, Z.G. Dai 1 and T. Lu 1, 2

1 Department of Astronomy, Nanjing University, Nanjing 210093, P.R. China
2 CCAST, Beijing 100080, P.R. China

Received 15 June 1998 / Accepted 6 July 1998

Abstract

Postburst evolution of adiabatic fireballs that produce [FORMULA]-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 [FORMULA] d, implying a large initial energy [FORMULA], 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: tlu@nju.edu.cn)

© European Southern Observatory (ESO) 1998

Online publication: July 27, 1998

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