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We analyse high-resolution near-UV and optical spectra of the afterglow of GRB 080310, obtained with the Very Large Telescope Ultraviolet and Visual Echelle Spectrograph (VLT/UVES), to investigate the circumburst environment and the…

We study the Gamma Ray Burst (GRB) environment and intervening absorbers by analyzing the optical absorption features produced by gas surrounding the GRB or along its line of sight. We analyzed high resolution spectroscopic observations…

We analyze high resolution spectroscopic observations of the optical afterglow of GRB050730, obtained with UVES@VLT about hours after the GRB trigger. The spectrum shows that the ISM of the GRB host galaxy at z = 3.967 is complex, with at…

Excited Si^+ and Fe^+ species are routinely observed in the host environment of gamma-ray burst (GRB) afterglows, but are not commonly seen in other extragalactic locations. Their presence signals unusual properties in the gaseous…

We present early time, high resolution spectroscopy of three GRB afterglows: GRB050730, GRB050922C and GRB060418. These data give us precious information on the kinematics, ionization and metallicity of the interstellar matter of GRB host…

We present sequential optical spectra of the afterglow of GRB 010222 obtained one day apart using the Low Resolution Imaging Spectrometer (LRIS) and the Echellette Spectrograph and Imager (ESI) on the Keck telescopes. Three low-ionization…

We present time-resolved optical spectroscopy of the afterglows of the gamma-ray bursts GRB 990510 and GRB 990712. Through the identification of several absorption lines in the first epoch GRB 990510 spectrum, we determine the redshift for…

The gamma-ray burst (GRB) 050904 at z = 6.3 provides the first opportunity of probing the intergalactic medium (IGM) by GRBs at the epoch of the reionization. Here we present a spectral modeling analysis of the optical afterglow spectrum…

We present an analysis of fine-structure transitions of FeII and SiII detected in a high-resolution optical spectrum of the afterglow of GRB 051111 (z=1.54948). The fine-structure absorption features arising from FeII* to FeII****, as well…

(Abridged) We use VLT/UVES high-resolution optical spectroscopy of seven GRB afterglows at z_GRB>2 to investigate circumburst and interstellar plasma in the host galaxies. Our sample consists of GRBs 021004, 050730, 050820, 050922C, 060607,…

We study the gamma-ray burst GRB 081008 environment by analysing the spectra of its optical afterglow. UVES high resolution spectroscopy of GRB 081008 was secured ~5 hr after the Swift trigger. Our dataset comprises also three FORS2 nearly…

We investigate properties of the interstellar medium (ISM) in galaxies hosting long-duration gamma-ray bursts (GRBs) from an analysis of atomic species (MgI, FeI) and excited fine-structure levels of ions (e.g. SiII). Our analysis is guided…

Gamma-ray bursts are the most energetic known explosions. Despite fading rapidly, they allow to measure redshift and important properties of their host-galaxies. We report the photometric and spectroscopic study of GRB 160203A and its…

We study the GRB 081008 environment with simultaneous high- and low-resolution spectroscopy using UVES and FORS2 data acquired ~5 hr after the Swift trigger. The interstellar medium (ISM) of the host galaxy at z=1.9683 is constituted by at…

We compare the HI column densities from Ly-alpha absorption to the metal column densities from X-ray absorption in gamma-ray burst (GRB) afterglows. Eight bursts of seventeen entering the sample, have significant extragalactic X-ray…

We report on follow-up observations of the GRB 060927 using the ROTSE-IIIa telescope and a suite of larger aperture ground-based telescopes. An optical afterglow was detected 20 s after the burst, the earliest rest-frame detection of…

We present high time resolution (1.09 s) photometry of GRB 080210 obtained with ULTRASPEC mounted on the ESO/3.6-m telescope, starting 68.22 min after the burst and lasting for 26.45 min. The light curve is smooth on both short (down to…

The optical afterglow of long-duration GRB 071003 is among the brightest yet to be detected from any GRB, with R ~ 12 mag in KAIT observations starting 42 s after the GRB trigger, including filtered detections during prompt emission.…

We present broadband multi-wavelength observations of GRB 080310 at redshift z = 2.43. This burst was bright and long-lived, and unusual in having extensive optical and near IR follow-up during the prompt phase. Using these data we attempt…

The aim of this paper is to investigate the properties of the intervening absorbers lying along the line of sight of Gamma-Ray Burst (GRB) 080319B through the analysis of its optical absorption features. To this purpose, we analyze a…