Gamma-ray bursts: optical afterglows in the deep Newtonian phase |
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Authors: | Y F Huang K S Cheng |
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Affiliation: | Department of Astronomy, Nanjing University, Nanjing 210093, China;Department of Physics, The University of Hong Kong, Pokfulam Road, Hong Kong, China;LCRHEA, Institute for High-Energy Physics, Chinese Academy of Sciences, Beijing 100039, China |
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Abstract: | Gamma-ray burst remnants become trans-relativistic typically in days to tens of days, and they enter the deep Newtonian phase in tens of days to months, during which the majority of shock-accelerated electrons will no longer be highly relativistic. However, a small portion of electrons are still accelerated to ultra-relativistic speeds and are capable of emitting synchrotron radiation. The distribution function for electrons is re-derived here so that synchrotron emission from these relativistic electrons can be calculated. Based on the revised model, optical afterglows from both isotropic fireballs and highly collimated jets are studied numerically, and compared to analytical results. In the beamed cases, it is found that, in addition to the steepening due to the edge effect and the lateral expansion effect, the light curves are universally characterized by a flattening during the deep Newtonian phase. |
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Keywords: | radiation mechanisms: non-thermal stars: neutron ISM: jets and outflows gamma-rays: bursts |
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