All Figures

$\begin{figure} \par\includegraphics[width=14.4cm,clip]{3795fig1.ps} \end{figure}$ Figure 1: Top panel: the optical spectrum of the afterglow of GRB 991216, taken 1.5 days after the burst. The resolution is approximately 24 Å across the entire spectrum, which corresponds to a resolving power of 250 at 6000 Å. The spectrum has not been smoothed. The blue and red spectra (respectively without and with the OG590 order sorting filter) are connected at 6200 Å. The two strong absorption lines longward of 6000 Å are telluric. The spectrum flux has been increased by 10% to match the ${\it VRI}$ photometric points of Halpern et al. (2000), indicated with the open circles; the horizontal error bars reflect the FWHM of the filter transmission profiles. We have fit MW-, LMC- and SMC-type extinction curves to the spectrum, shown by the solid (MW), dashed (LMC) and dotted (SMC) lines in both panels (see text). The dash-dotted line shows the MW fit assuming that the bump is centered at 2360 Å. Bottom panel: a blow-up of the top spectrum, over the wavelength ranges 4000-5900 Å and 7800-8200 Å. For the latter range, we also plot the combined blue and red spectra (offset by 30 $\mu$ Jy for clarity) below the red-only spectrum. We have identified several strong rest-frame UV absorption features, which are indicated with short solid lines. Based on the inferred redshifts of these features, there seem to be numerous weaker lines, indicated with short dashed lines. The lower line identification labels correspond to the z=1.02 system, the middle ones to z=0.80 and the top ones to z=0.77 (see also Table 2). For both panels, the 1 $\sigma$ Poisson error spectrum is also plotted (solid line at the bottom).
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In the text

$\begin{figure} \par\includegraphics[width=8.1cm,clip]{3795fig2.ps} \end{figure}$ Figure 2: The sum of the HST/STIS 50CCD and LP images of the field of GRB 991216. The position of the early optical transient is marked with a black circle, with an error radius of 0 $.\!\!^{\prime\prime}$ 05 (2 drizzled HST pixels). The regions A and B could be part of the same galaxy at z=1.02, or two systems in the process of merging. Based on the identification of at least two absorption-line systems in the spectrum, an alternative configuration is that A is the host galaxy of GRB 991216 at z=1.02, and that B is responsible for the absorption lines at z=0.80. Either one of the galaxies that are located 2 $^{\prime \prime }$ to the SE and NW of the transient position could be the counterpart of the tentative z=0.77 system.
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In the text

$\begin{figure} \par\includegraphics[width=13.9cm,clip]{3795fig3.ps} \end{figure}$ Figure 3: The optical spectrum of the afterglow of GRB 011211, smoothed with a boxcar the size of 3 pixels, or about 8 Å. The resolution is approximately 10 Å across the entire spectrum, which corresponds to a resolving power of 600 at 6000 Å. The spectrum flux level has been scaled downward by 70% to match the photometric ${\it UBVRI}$ data points of Jakobsson et al. (2003), which are shown by the open circles. With one exception, all significant (3 $\sigma$ ) features (see Table 3) can be identified with Ly $\alpha$ and metal-absorption lines in a single system, the host galaxy, at a redshift of $z=2.1418\pm 0.0018$ . The lack of Ly $\alpha$ -forest lines redward of Ly $\alpha$ shows that GRB 011211 occurred at this redshift. The bottom solid line shows the 1 $\sigma$ Poisson error.
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In the text

$\begin{figure} \par\includegraphics[width=7.9cm,clip]{3795fig4.ps} \end{figure}$ Figure 4: The fit (solid continuous line) of the Ly $\alpha$ line to the normalised spectrum of GRB 011211 (solid histogram), resulting in log N(H I) = $20.4\pm 0.2$ . The dotted lines show the 1 $\sigma$ errors of the fit, and the long-dashed line indicates the 1 $\sigma$ Poisson error spectrum.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{3795fig5.ps} \end{figure}$ Figure 5: The curve of growth for the absorption lines measured in the afterglow of GRB 011211.
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In the text

$\begin{figure} \par\includegraphics[width=14.3cm,clip]{3795fig6.ps} \end{figure}$ Figure 6: The optical spectrum of the probable host galaxy of GRB 021211. The spectrum has neither been flux calibrated nor smoothed. The resolution is approximately 11 Å across the entire spectrum, which corresponds to a resolving power of 550 at 6000 Å. The top panel shows the S/N spectrum, smoothed with a boxcar with a size similar to the spectral resolution. Only 1 significant line is detected, at 7478 Å, which is most likely [O II] $\lambda$ 3727 at a redshift of z=1.006. The 1 $\sigma$ Poisson error spectrum is also plotted in the bottom panel.
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In the text

$\begin{figure} \par\includegraphics[width=14.3cm,clip]{3795fig7.ps} \end{figure}$ Figure 7: The optical spectrum of the galaxy 1 $.\!\!^{\prime\prime}$ 5 to the North-East of the GRB 021211 afterglow location. The resolution is approximately 11 Å across the entire spectrum, which corresponds to a resolving power of 550 at 6000 Å. The spectrum has neither been flux calibrated nor smoothed. The top panel shows the S/N per pixel spectrum. The significant lines can be identified with [O II] $\lambda$ 3727, [Ne III] $\lambda$ 3968, H $\beta$ and [O III] $\lambda$ $\lambda$ 4959, 5007 at a redshift of z=0.800. The 1 $\sigma$ Poisson error spectrum is also plotted in the bottom panel.
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In the text

$\begin{figure} \par\includegraphics[width=7.9cm,clip]{3795fig4.ps} \end{figure}$	Figure 4: The fit (solid continuous line) of the Ly $\alpha$ line to the normalised spectrum of GRB 011211 (solid histogram), resulting in log N(H I) = $20.4\pm 0.2$ . The dotted lines show the 1 $\sigma$ errors of the fit, and the long-dashed line indicates the 1 $\sigma$ Poisson error spectrum.
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$\begin{figure} \par\includegraphics[width=8cm,clip]{3795fig5.ps} \end{figure}$	Figure 5: The curve of growth for the absorption lines measured in the afterglow of GRB 011211.
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