A flash in the dark: UVES/VLT high resolution spectroscopy of GRB afterglows
Abstract
We present the first high resolution (R=20000--45000, corresponding to 14 km/s at 4200A to 6.6 km/s at 9000A) observations of the optical afterglow of Gamma Ray Bursts. GRB020813 and GRB021004 were observed by UVES@VLT 22.19 hours and 13.52 hours after the trigger, respectively. These spectra show that the inter--stellar matter of the GRB host galaxies is complex, with many components contributing to each main absorption system, and spanning a total velocity range of up to about 3000 km/s. Several narrow components are resolved down to a width of a few tens of km/s. In the case of GRB021004 we detected both low and high ionization lines. Combined with photoionization results obtained with CLOUDY, the ionization parameters of the various systems are consistent with a remarkably narrow range with no clear trend with system velocity. This can be interpreted as due to density fluctuations on top of a regular R^-2 wind density profile.
Keywords
Cite
@article{arxiv.astro-ph/0409717,
title = {A flash in the dark: UVES/VLT high resolution spectroscopy of GRB afterglows},
author = {F. Fiore and V. D'Elia and D. Lazzati and R. Perna and L. Sbordone and G. Stratta and E. J. A. Meurs and P. Ward and L. A. Antonelli and G. Chincarini and S. Covino and A. Di Paola and A. Fontana and G. Ghisellini and G. Israel and F. Frontera and G. Marconi and L. Stella and M. Vietri and F. Zerbi},
journal= {arXiv preprint arXiv:astro-ph/0409717},
year = {2009}
}
Comments
Most figure improved, a few typos corrected, added a new subsection. ApJ in press