158 articles – 1990 Notices  [english version]
 HAL : in2p3-00124483, version 1
 arXiv : astro-ph/0612607
 Astronomy and Astrophysics Letters 469 (2007) L13-L16
 REM observations of GRB 060418 and GRB 060607A: the onset of the afterglow and the initial fireball Lorentz factor determination
 (2007)
 Gamma-ray burst (GRB) emission is believed to originate in highly relativistic fireballs. Currently, only lower limits were securely set to the initial fireball Lorentz factor Gamma_0. We aim to provide a direct measure of Gamma_0. The early-time afterglow light curve carries information about Gamma_0, which determines the time of the afterglow peak. We have obtained early observations of the near-infrared afterglows of GRB 060418 and GRB 060607A with the REM robotic telescope. For both events, the afterglow peak could be clearly singled out, allowing a firm determination of the fireball Lorentz of Gamma_0 ~ 400, fully confirming the highly relativistic nature of GRB fireballs. The deceleration radius was inferred to be R_dec ~ 10^17 cm. This is much larger than the internal shocks radius (believed to power the prompt emission), thus providing further evidence for a different origin of the prompt and afterglow stages of the GRB.
 équipe(s) de recherche : APC - AHEHELFA
 Thème(s) : Physique/Astrophysique/Cosmologie et astrophysique extra-galactiquePlanète et Univers/Astrophysique/Cosmologie et astrophysique extra-galactiquePlanète et Univers/Astrophysique
 Lien vers le texte intégral : http://fr.arXiv.org/abs/astro-ph/0612607
 in2p3-00124483, version 1 http://hal.in2p3.fr/in2p3-00124483 oai:hal.in2p3.fr:in2p3-00124483 Contributeur : Simone Lantz <> Soumis le : Lundi 15 Janvier 2007, 12:20:32 Dernière modification le : Lundi 18 Juin 2012, 16:37:51