On the jet structure and magnetic field configuration of GRB 020813
Abstract
The polarization curve of GRB 020813 is discussed and compared to different models for the structure, evolution and magnetisation properties of the jet and the interstellar medium onto which the fireball impacts. GRB 020813 is best suited for this kind of analysis for the smoothness of its afterglow light curve, ensuring the applicability of current models. The polarization dataset allows us to rule out the standard GRB jet, in which the energy and Lorentz factor have a well defined value inside the jet opening angle and the magnetic field is generated at the shock front. We explore alternative models finding that a structured jet or a jet with a toroidal component of the magnetic field can fit equally well the polarization curve. Stronger conclusions cannot be drawn due to the incomplete sampling of the polarization curve. A more dense sampling, especially at early times, is required to pin down the structure of the jet and the geometry of its magnetic field.
Cite
@article{arxiv.astro-ph/0401315,
title = {On the jet structure and magnetic field configuration of GRB 020813},
author = {D. Lazzati and S. Covino and J. Gorosabel and E. Rossi and G. Ghisellini and E. Rol and J. M. Castro Cerón and A. J. Castro-Tirado and M. Della Valle and S. di Serego Alighieri and A. S. Fruchter and J. P. U. Fynbo and P. Goldoni and J. Hjorth and G. L. Israel and L. Kaper and N. Kawai and E. Le Floc'h and D. Malesani and N. Masetti and P. Mazzali and F. Mirabel and P. Moller and S. Ortolani and E. Palazzi and E. Pian and J. Rhoads and G. Ricker and J. D. Salmonson and L. Stella and G. Tagliaferri and N. Tanvir and E. van den Heuvel and R. A. M. J. Wijers and F. M. Zerbi},
journal= {arXiv preprint arXiv:astro-ph/0401315},
year = {2008}
}
Comments
7 pages, 5 postscript figures, minor revisions according to the referee comments. A&A in press