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Extinction properties of the X-ray bright/optically faint afterglow of GRB 020405

G. Stratta·R. Perna·D. Lazzati·F. Fiore·L. A. Antonelli·M. L. Conciatore
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Abstract

We present an optical-to-X-ray spectral analysis of the afterglow of GRB 020405. The optical spectral energy distribution not corrected for the extragalactic extinction is significantly below the X-ray extrapolation of the single powerlaw spectral model suggested by multiwavelength studies. We investigate whether considerable extinction could explain the observed spectral ``mismatch'' by testing several types of extinction curves. For the first time we test extinction curves computed with time-dependent numerical simulations of dust grains destruction by the burst radiation. We find that an extinction law weakly depen dent on wavelength can reconcile the unabsorbed optical and X-ray data with the expected synchrotron spectrum. A gray extinction law can be provided by a dust grain size distribution biased toward large grains.

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G. Stratta, R. Perna, D. Lazzati, F. Fiore, L. A. Antonelli, M. L. Conciatore. 2005-06-17. Extinction properties of the X-ray bright/optically faint afterglow of GRB 020405. https://doi.org/10.1051/0004-6361%3A20053302

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