All Figures

$\begin{figure} \par\includegraphics[width=7.6cm,clip]{3913fig1.ps} \end{figure}$ Figure 1: The background-subtracted BAT light curve in the 20-150 keV energy band. The origin of the time axis was set to the instrument trigger, but a weak peak is apparent ${\approx } 9$ s before the BAT trigger.
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{3913fig2.ps} \par\end{figure}$ Figure 2: XRT image of the field of GRB 050326, smoothed with a Gaussian kernel (4 $.\!\!^{\prime\prime}$ 7 full width half maximum). Events were accumulated from the first segment of the observation (589 s exposure time). The BAT refined position (black dot) is also shown together with its 95% containment error circle (3 $^\prime$ radius, dashed line). The XRT and XMM-Newton positions (1 $.\!\!^{\prime\prime}$ 7 apart) are also plotted (crosses), and are almost indistinguishable. The X-ray error circles (3 $.\!\!^{\prime\prime}$ 6 and 1 $.\!\!^{\prime\prime}$ 5 radius, respectively) are too small to be seen on this scale.
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In the text

$\begin{figure} \par\includegraphics[width=13cm,clip]{3913fig3.ps} \end{figure}$ Figure 3: The light curve of GRB 050326 and of its afterglow in the 0.3-8 keV energy band (see text for the computation of the flux conversion factors). XRT (black circles) and XMM-Newton data (empty diamonds) show a very good agreement (see also the inset). The solid line shows the fit to the combined XRT/XMM afterglow light curve. The dotted lines indicate the 90% errors of the extrapolated X-ray light curve. Light filled circles indicate the extrapolation of the BAT data to the 0.3-8 keV energy range, assuming the Band model as the best-fit spectrum. In this figure, the time origin was set 10 s before the nominal trigger time, to show the weak, untriggered precursor. This has no effect on the determination of the afterglow decay slope, due to the late beginning of the XRT observation.
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In the text

$\begin{figure} \par\includegraphics[angle=270,width=12.5cm,clip]{3913fig4.ps} \end{figure}$ Figure 4: The spectra of the GRB 050326 afterglow as observed by XMM-Newton (PN: squares; MOS1: open circles; MOS2: triangles) and by Swift-XRT (filled circles). The solid lines represent the best-fit absorbed power-law model convolved with the instrumental responses (see Table 2 for the best-fit parameters). XRT data were selected from the time interval covered by the XMM-Newton observation.
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In the text

$\begin{figure} \par\includegraphics[angle=270,width=7.5cm,clip]{3913fig5.ps} \end{figure}$ Figure 5: Confidence contours (68%, 90% and 99% levels for 2 parameters of interest) for the gas column density $N_{{\rm H},z}$ and the redshift z of the intrinsic absorber, as computed from the fit to the EPIC spectra. The Galactic column density was assumed to be $N_{\rm H,MW} = 4.6 \times 10^{20}$ cm^-2 (Dickey & Lockman 1990). The inset shows a zoom-in of the low-redshift region.
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In the text

$\begin{figure} \par\includegraphics[width=10cm,clip]{3913fig6.ps} \end{figure}$ Figure 6: Comparison of GRB 050326 with the Amati ( right) and Ghirlanda ( left) relations (Ghirlanda et al. 2004; Amati et al. 2002). The thick solid curves (black and grey) show the position of GRB 050326 as its redshift varies in the interval 0.1 < z < 10. The Ghirlanda track is actually a boundary (as the horizontal arrows indicate), since we can infer only a lower limit to the beaming-corrected energy at each redshift. Filled circles and squares indicate the GRBs which define the above two relations, plotted as straight solid lines (together with their 1-, 2- and 3- $\sigma$ contours: long-dashed, dot-dashed and dotted lines, respectively). Data were taken from Ghirlanda et al. (2004,2005). Grey diamonds indicate the intersection of the GRB 050326 tracks with the 3- $\sigma$ contours of the Amati and Ghirlanda relations. These points thus define the 3- $\sigma$ redshift ranges for which GRB 050326 was consistent with the two relations. In the two GRB 050326 tracks, the region 1.5 < z < 8 (indicated by the X-ray data) is shown in black, bound by asterisks.
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In the text

$\begin{figure} \par\includegraphics[width=7cm,clip]{3913fig7.ps} \end{figure}$ Figure 7: Broad-band spectral energy distribution of the afterglow of GRB 050326, computed at different times (which are identified by different symbols). The shape of the X-ray spectrum was assumed to be constant throughout the observation, and the decay law was adopted to report the X-ray flux at the time of the optical measurements.
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In the text

$\begin{figure} \par\includegraphics[width=7.6cm,clip]{3913fig1.ps} \end{figure}$	Figure 1: The background-subtracted BAT light curve in the 20-150 keV energy band. The origin of the time axis was set to the instrument trigger, but a weak peak is apparent ${\approx } 9$ s before the BAT trigger.
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$\begin{figure} \par\includegraphics[angle=270,width=7.5cm,clip]{3913fig5.ps} \end{figure}$	Figure 5: Confidence contours (68%, 90% and 99% levels for 2 parameters of interest) for the gas column density $N_{{\rm H},z}$ and the redshift z of the intrinsic absorber, as computed from the fit to the EPIC spectra. The Galactic column density was assumed to be $N_{\rm H,MW} = 4.6 \times 10^{20}$ cm^-2 (Dickey & Lockman 1990). The inset shows a zoom-in of the low-redshift region.
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$\begin{figure} \par\includegraphics[width=7cm,clip]{3913fig7.ps} \end{figure}$	Figure 7: Broad-band spectral energy distribution of the afterglow of GRB 050326, computed at different times (which are identified by different symbols). The shape of the X-ray spectrum was assumed to be constant throughout the observation, and the decay law was adopted to report the X-ray flux at the time of the optical measurements.
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