Gamma-ray bursts: post-burst evolution of fireballs |
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| Authors: | Y F Huang Z G Dai D M Wei & T Lu |
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| Institution: | Department of Astronomy, Nanjing University, Nanjing 210093, China,;Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008, China,;CCAST (World Laboratory) PO Box 8730, Beijing 100080, China,;LCRHEA, IHEP, CAS, Beijing, China |
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| Abstract: | The post-burst evolution of fireballs that produce γ-ray bursts (GRBs) is studied, assuming the expansion of fireballs to be adiabatic and relativistic. Numerical results as well as an approximate analytic solution for the evolution are presented. Owing to the adoption of a new relation between t R and γ, our results differ markedly from previous studies. Synchrotron radiation from the shocked interstellar medium is carefully calculated, using a conventional set of equations. The observed X-ray flux of GRB afterglows can be reproduced easily. Although the optical afterglows seem much more complicated, our results can still present a rather satisfactory agreement with observations. We also find that the expansion will no longer be highly relativistic about 4 d after the main GRB. We thus suggest that the marginally relativistic phase of the expansion should be investigated so as to check the afterglows observed a week or more later. |
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| Keywords: | relativity shock waves gamma-rays: bursts |
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