All Figures

$\begin{figure} \par\includegraphics[width=8.1cm,clip]{5283Fig1.ps} \end{figure}$ Figure 1: X-ray light curve of GRB 050721 afterglow in the 0.2-10 keV energy band. Empty squares and filled circles indicate WT and PC data, respectively. The curve is background-subtracted and the time is referred to the BAT trigger, 2005 Jul. 21 at 04:29:14.28 UT. The solid line shows the best-fit broken power law (see Sect. 3.2). The last point is a 3- $\sigma$ upper limit.
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In the text

$\begin{figure} \par\includegraphics[angle=270,width=7.9cm,clip]{5283Fig2.ps} \end{figure}$ Figure 2: X-ray spectrum of the afterglow of GRB 050721. Top: spectra of WT (filled circles) and PC data (empty squares) fitted with an absorbed power law model. Bottom: residuals from the simultaneous power-law fit to all the data.
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In the text

$\begin{figure} \par\includegraphics[angle=270,width=7.5cm,clip]{5283Fig3.ps} \end{figure}$ Figure 3: Contour plot of the column density vs. the power law photon index for the X-ray spectrum of GRB 050721. The contours refer to 1-, 2- and 3- $\sigma$ confidence levels. The Galactic column density ( $1.60 \times 10^{21}$ cm^-2; Kalberla et al. 2005) is reported with an uncertainty of 15% (solid vertical lines).
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{5283Fig4.ps}\end{figure}$ Figure 4: VLT image of the field of the afterglow of GRB 050721, showing the proximity with the USNO star and the fading behavior of the optical transient.
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In the text

$\begin{figure} \par\includegraphics[width=8.4cm,clip]{5283Fig5.ps} \end{figure}$ Figure 5: The R-band light curve of the early afterglow of GRB 050721 observed with VLT equipped with FORS 2. Optical data can be fitted by a simple power law model ( $F(t)\propto t^{-\alpha }$ ) with $\alpha = 1.29 \pm 0.06$ (dotted line). This slope is in good agreement with the X-ray slope at the same time.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{5283Fig6.ps} \end{figure}$ Figure 6: Multiwavelength light curve of the afterglow of GRB 050721: from top to bottom: I band (black filled triangles), R band (red filled squares), B band (blue filled circles), X-flux at 1 keV (black open circles). Vertical dashed lines show the times of the SEDs in Fig. 7.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{5283Fig7.ps} \end{figure}$ Figure 7: Spectral energy distribution of the afterglow of GRB 050721 before the optical bump (t=8420 s) and at the time of the optical bump (t=76 160 s). Early optical and X-ray fluxes are artificially shifted up by a factor of 10 to distance them from the later time points.
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In the text

$\begin{figure} \par\includegraphics[width=8.1cm,clip]{5283Fig1.ps} \end{figure}$	Figure 1: X-ray light curve of GRB 050721 afterglow in the 0.2-10 keV energy band. Empty squares and filled circles indicate WT and PC data, respectively. The curve is background-subtracted and the time is referred to the BAT trigger, 2005 Jul. 21 at 04:29:14.28 UT. The solid line shows the best-fit broken power law (see Sect. 3.2). The last point is a 3- $\sigma$ upper limit.
Open with DEXTER

$\begin{figure} \par\includegraphics[angle=270,width=7.9cm,clip]{5283Fig2.ps} \end{figure}$	Figure 2: X-ray spectrum of the afterglow of GRB 050721. Top: spectra of WT (filled circles) and PC data (empty squares) fitted with an absorbed power law model. Bottom: residuals from the simultaneous power-law fit to all the data.
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$\begin{figure} \par\includegraphics[angle=270,width=7.5cm,clip]{5283Fig3.ps} \end{figure}$	Figure 3: Contour plot of the column density vs. the power law photon index for the X-ray spectrum of GRB 050721. The contours refer to 1-, 2- and 3- $\sigma$ confidence levels. The Galactic column density ( $1.60 \times 10^{21}$ cm^-2; Kalberla et al. 2005) is reported with an uncertainty of 15% (solid vertical lines).
Open with DEXTER

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{5283Fig4.ps}\end{figure}$	Figure 4: VLT image of the field of the afterglow of GRB 050721, showing the proximity with the USNO star and the fading behavior of the optical transient.
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$\begin{figure} \par\includegraphics[width=8.4cm,clip]{5283Fig5.ps} \end{figure}$	Figure 5: The R-band light curve of the early afterglow of GRB 050721 observed with VLT equipped with FORS 2. Optical data can be fitted by a simple power law model ( $F(t)\propto t^{-\alpha }$ ) with $\alpha = 1.29 \pm 0.06$ (dotted line). This slope is in good agreement with the X-ray slope at the same time.
Open with DEXTER

$\begin{figure} \par\includegraphics[width=8cm,clip]{5283Fig6.ps} \end{figure}$	Figure 6: Multiwavelength light curve of the afterglow of GRB 050721: from top to bottom: I band (black filled triangles), R band (red filled squares), B band (blue filled circles), X-flux at 1 keV (black open circles). Vertical dashed lines show the times of the SEDs in Fig. 7.
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$\begin{figure} \par\includegraphics[width=8cm,clip]{5283Fig7.ps} \end{figure}$	Figure 7: Spectral energy distribution of the afterglow of GRB 050721 before the optical bump (t=8420 s) and at the time of the optical bump (t=76 160 s). Early optical and X-ray fluxes are artificially shifted up by a factor of 10 to distance them from the later time points.
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