We measured the fireball Lorentz factor of GRB 060418 by the direct observation of the onset of the NIR afterglow carried with the REM telescope. We found a value of about 400.
@article{arxiv.astro-ph/0701688,
title = {REM observations of GRB 060418: the fireball Lorentz factor determination},
author = {S. D. Vergani},
journal= {arXiv preprint arXiv:astro-ph/0701688},
year = {2010}
}
Comments
2 pages, 1 eps figure. Proceedings of the "Swift and GRBs: Unveiling the Relativistic Universe" meeting, Venice, June 5-9, 2006, to be published by "Il Nuovo Cimento"