During the first decade after the discovery of the first GRB afterglow, optical light curves have been considered to be characterised by a quite smooth behaviour, usually being well described with single or broken power law decays from some hours up to weeks after the trigger. Only a few densely sampled events showed re-brightenings or fluctuations around the power law continuum in the optical. After the launch of Swift, the optical light curve smoothness paradigm has been questioned thanks to the faster and richer available optical follow up. That triggered the interest of the whole GRB community. GRB 081029 is an outstanding example of this standard view crisis. Its optical-NIR light curve is characterised by an extremely sharp intense re-brightening at late times that cannot be explained in the framework of the simplest standard fireball models. Thanks to the 7-band contemporaneous imager GROND, we have been able to follow the temporal and spectral evolution of this afterglow with an unprecedented resolution. This leads us to rule out some of the most common models proposed for explaining the re-brightenings and to constrain alternative scenarios (late time central engine activity vs. environment properties). After 3 years of activity, the capabilities of GROND are showing that this behaviour not unique making GRB 081029 a fundamental laboratory for interpreting the afterglow emission processes. © 2011 American Institute of Physics.
Nardini, M., Greiner, J., Klose, S., Krühler, T., Filgas, R., Schady, P., et al. (2011). What can produce a sharp late time optical re-brightening? Optical bumps in the multi-color imaging era. In Gamma ray bursts 2010 (pp.150-153). Melville, New York : AIP [10.1063/1.3621759].
What can produce a sharp late time optical re-brightening? Optical bumps in the multi-color imaging era
NARDINI, MARCO;
2011
Abstract
During the first decade after the discovery of the first GRB afterglow, optical light curves have been considered to be characterised by a quite smooth behaviour, usually being well described with single or broken power law decays from some hours up to weeks after the trigger. Only a few densely sampled events showed re-brightenings or fluctuations around the power law continuum in the optical. After the launch of Swift, the optical light curve smoothness paradigm has been questioned thanks to the faster and richer available optical follow up. That triggered the interest of the whole GRB community. GRB 081029 is an outstanding example of this standard view crisis. Its optical-NIR light curve is characterised by an extremely sharp intense re-brightening at late times that cannot be explained in the framework of the simplest standard fireball models. Thanks to the 7-band contemporaneous imager GROND, we have been able to follow the temporal and spectral evolution of this afterglow with an unprecedented resolution. This leads us to rule out some of the most common models proposed for explaining the re-brightenings and to constrain alternative scenarios (late time central engine activity vs. environment properties). After 3 years of activity, the capabilities of GROND are showing that this behaviour not unique making GRB 081029 a fundamental laboratory for interpreting the afterglow emission processes. © 2011 American Institute of Physics.
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