TY - JOUR
T1 - Physics of the GRB 030328 afterglow and its environment
AU - Maiorano, E.
AU - Masetti, N.
AU - Palazzi, E.
AU - Savaglio, S.
AU - Rol, E.
AU - Vreeswijk, P. M.
AU - Pian, E.
AU - Price, P. A.
AU - Peterson, B. A.
AU - Jelínek, M.
AU - Amati, L.
AU - Andersen, M. I.
AU - Castro-Tirado, A. J.
AU - Cerón, J. M.Castro
AU - De Ugarte Postigo, A.
AU - Frontera, F.
AU - Fruchter, A. S.
AU - Fynbo, J. P.U.
AU - Gorosabel, J.
AU - Henden, A. A.
AU - Hjorth, J.
AU - Jensen, B. L.
AU - Klose, S.
AU - Kouveliotou, C.
AU - Masi, G.
AU - Møller, P.
AU - Nicastro, L.
AU - Ofek, E. O.
AU - Pandey, S. B.
AU - Rhoads, J.
AU - Tanvir, N. R.
AU - Wijers, R. A.M.J.
AU - Van Den Heuvel, E. P.J.
PY - 2006/8
Y1 - 2006/8
N2 - Aims. To investigate the physical nature of the afterglow emission. We report on the photometric, spectroscopic and polarimetric observations of the optical afterglow of Gamma-Ray Burst (GRB) 030328 detected by HETE-2. Methods. Photometric, spectroscopic and polarimetric monitoring of the optical afterglow. Results. Photometry, collected at 7 different telescopes, shows that a smoothly broken powerlaw decay, with indices α1 = 0.76 ± 0.03, α2 = 1.50 ±0.07 and a break at tb = 0.48 ±0.03 days after the GRB, provides the best fit of the optical afterglow decline. This shape is interpreted as due to collimated emission, for which we determine a jet opening angle θjet ∼ 3°.2. An achromatic bump starting around ∼0.2 d after the GRB is possibly marginally detected in the optical light curves. Optical spectroscopy shows the presence of two rest-frame ultraviolet metal absorption systems at z = 1.5216 ± 0.0006 and at z = 1.295 ± 0.001, the former likely associated with the GRB host galaxy. Analysis of the absorption lines at z = 1.5216 suggests that the host of this GRB may be a Damped Lyman-α Absorber. The optical V-band afterglow appears polarized, with P - (2.4 ±0.6)% and θ = 170° ± 7°, suggesting an asymmetric blastwave expansion. An X-ray-to-optical spectral flux distribution of the GRB 030328 afterglow was obtained at 0.78 days after the GRB and fitted using a broken powerlaw, with an optical spectral slope βopt = 0.47 ± 0.15, and an X-ray slope βx = 1.0 ± 0.2. Conclusions. The discussion of the results in the context of the "fireball model" shows that the preferred scenario for this afterglow is collimated structured jet with fixed opening angle in a homogeneous medium.
AB - Aims. To investigate the physical nature of the afterglow emission. We report on the photometric, spectroscopic and polarimetric observations of the optical afterglow of Gamma-Ray Burst (GRB) 030328 detected by HETE-2. Methods. Photometric, spectroscopic and polarimetric monitoring of the optical afterglow. Results. Photometry, collected at 7 different telescopes, shows that a smoothly broken powerlaw decay, with indices α1 = 0.76 ± 0.03, α2 = 1.50 ±0.07 and a break at tb = 0.48 ±0.03 days after the GRB, provides the best fit of the optical afterglow decline. This shape is interpreted as due to collimated emission, for which we determine a jet opening angle θjet ∼ 3°.2. An achromatic bump starting around ∼0.2 d after the GRB is possibly marginally detected in the optical light curves. Optical spectroscopy shows the presence of two rest-frame ultraviolet metal absorption systems at z = 1.5216 ± 0.0006 and at z = 1.295 ± 0.001, the former likely associated with the GRB host galaxy. Analysis of the absorption lines at z = 1.5216 suggests that the host of this GRB may be a Damped Lyman-α Absorber. The optical V-band afterglow appears polarized, with P - (2.4 ±0.6)% and θ = 170° ± 7°, suggesting an asymmetric blastwave expansion. An X-ray-to-optical spectral flux distribution of the GRB 030328 afterglow was obtained at 0.78 days after the GRB and fitted using a broken powerlaw, with an optical spectral slope βopt = 0.47 ± 0.15, and an X-ray slope βx = 1.0 ± 0.2. Conclusions. The discussion of the results in the context of the "fireball model" shows that the preferred scenario for this afterglow is collimated structured jet with fixed opening angle in a homogeneous medium.
KW - Cosmology: observations
KW - Gamma rays: bursts
KW - Line: identification
KW - Radiation mechanisms: non-thermal
UR - http://www.scopus.com/inward/record.url?scp=33748422834&partnerID=8YFLogxK
U2 - 10.1051/0004-6361:20054728
DO - 10.1051/0004-6361:20054728
M3 - Article
SN - 0004-6361
VL - 455
SP - 423
EP - 431
JO - Astronomy and Astrophysics
JF - Astronomy and Astrophysics
IS - 2
ER -