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arXiv · astro-ph/0601293

The broadband afterglow of GRB 030328

Abstract

We here report on the photometric, spectroscopic and polarimetric monitoring of the optical afterglow of the Gamma-Ray Burst (GRB) 030328 detected by HETE-2. We found that a smoothly broken power-law decay provides the best fit of the optical light curves, with indices alpha_1 = 0.76 +/- 0.03, alpha_2 = 1.50 +/- 0.07, and a break at t_b = 0.48 +/- 0.03 d after the GRB. Polarization is detected in the optical V-band, with P = (2.4 +/- 0.6)% and theta = (170 +/- 7) deg. Optical spectroscopy shows the presence of two absorption systems at z = 1.5216 +/- 0.0006 and at z = 1.295 +/- 0.001, the former likely associated with the GRB host galaxy. The X-ray-to-optical spectral flux distribution obtained 0.78 days after the GRB was best fitted using a broken power-law, with spectral slopes beta_opt = 0.47 +/- 0.15 and beta_X = 1.0 +/- 0.2. The discussion of these results in the context of the "fireball model" shows that the preferred scenario is a fixed opening angle collimated expansion in a homogeneous medium.

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BibTeXRIS

E. Maiorano, N. Masetti, E. Palazzi, S. Savaglio, E. Rol, E. Pian, P. M. Vreeswijk, P. A. Price, B. A. Peterson, M. Jelinek, S. B. Pandey, M. I. Andersen, A. A. Henden. 2006-01-13. The broadband afterglow of GRB 030328. https://doi.org/10.1063/1.2207921

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