EDP Sciences
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Volume 367, Number 2, February IV 2001
Page(s) 501 - 505
Section Formation, structure and evolution of stars
DOI http://dx.doi.org/10.1051/0004-6361:20010062

A&A 367, 501-505 (2001)
DOI: 10.1051/0004-6361:20010062

Could the unusual optical afterglow of GRB 000301c arise from a non-relativistic shock with energy injection?

Z. G. Dai and T. Lu

Department of Astronomy, Nanjing University, Nanjing 210093, PR China

(Received 22 June 2000 / Accepted 13 November 2000 )

Recent observations on the gamma-ray burst (GRB) 000301c afterglow show that one sharp break appears in the global optical/IR light curves, and in particular the decay slope at late times is as steep as about -3.0. This unusual feature is clearly inconsistent with the standard afterglow shock model. Here we propose a non-standard model for the afterglow of GRB 000301c, in which an initial ultra-relativistic shock in a dense medium ("dirty environment") rapidly evolved to the non-relativistic phase in 1 day after the burst. During such a phase, the shock was refreshed by a strongly magnetized millisecond pulsar through magnetic dipole radiation. This refreshment led to flattening of the light curves. After the energy injection, the afterglow decayed as $\propto t^{-3.0}$ if the electron distribution index of the shocked medium, $p\approx 3.4$, derived from the optical spectrum. Therefore, our model can provide a plausible explanation for the peculiar optical/IR afterglow light curves of GRB 000301c.

Key words: gamma-rays: bursts -- shock waves

Offprint request: T. Lu, tlu@nju.edu.cn

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