All Figures

$\begin{figure} \par\includegraphics[angle=270,width=8cm]{4457fig1.eps} \end{figure}$ Figure 1: 15-350 keV mask-weighted (i.e. background subtracted) BAT lightcurve of GRB050126. The x-axis indicates the elapsed time in seconds from the BAT rate trigger.
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In the text

$\begin{figure} \par\includegraphics[angle=270,width=8.3cm]{4457fig2.eps} \end{figure}$ Figure 2: The XRT 0.2-10.0 keV decay light-curve for GRB050126. All data were taken in PC mode. The decay curve is well-fit by a broken power-law (solid line) with slope 2.52^+0.50_-0.22 at early times flattening to a slope of 1.0 after 424 s (Cash statistic = 26.1 for 20 data points). Also shown is a powerlaw fit to the decay light-curve accounting for the onset of the X-ray afterglow $t_{\rm a}$ (dashed line), i.e. $f_{\nu }\propto (t-t_{\rm a})^{-\alpha }$ , with a best-fit slope of $\alpha =1.08^{+0.09}_{-0.09}$ and $t_{\rm a}=105.1^{+9.1}_{-11.3}$ s and Cash statistic 31.7 for 20 data points. The green arrows at later times are $1\sigma$ upper limits.
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In the text

$\begin{figure} \par {\includegraphics[angle=270,width=8.3cm]{4457fig3.eps} }\end{figure}$ Figure 3: BAT-XRT decay light-curve for GRB050126 (0.2-10 keV, see text for details). Note that the early steep decline phase in the XRT light-curve joins smoothly with the late-time BAT data.
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In the text

$\begin{figure} \par {\includegraphics[angle=270,width=8.5cm]{4457fig4.eps} }\end{figure}$ Figure 4: Combined power-law fit to the BAT (20-150 keV) and pre-break XRT (0.2-10 keV) spectra of GRB050126. The data are inconsistent with a single powerlaw fit at greater than >99% confidence. Inset: 68%, 90%, 95%, and 99% confidence contours indicating the Photon indices for BAT and XRT PC mode data in a combined fit to the BAT and XRT spectra for GRB050126. The data are inconsistent with a single power-law fit to the BAT and XRT spectra at >99%confidence.
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In the text

$\begin{figure} \par {\includegraphics[angle=270,width=8cm]{4457fig5.eps} }\end{figure}$ Figure 5: 15-350 keV mask-weighted BAT lightcurve of GRB050219a. The dotted lines (segments 1-5) indicate the time-slices used for the BAT spectral evolution analysis. Zero represents the BAT rate trigger time.
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In the text

$\begin{figure} \par {\includegraphics[angle=270,width=8cm]{4457fig6.eps} }\end{figure}$ Figure 6: Cross-correlation functions indicating the interband delays in 4 BAT channels for GRB050219a. The light-curves are highly correlated with the hardest bands leading the softer bands by $0.7\pm 0.1$ s (band 4 - band 3), $1.3\pm 0.1$ s (band 3 - band 2), and $2.7\pm 0.1$ s (band 2 - band 1) respectively.
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In the text

$\begin{figure} \par {\includegraphics[angle=270,width=8cm]{4457fig7.eps} } \end{figure}$ Figure 7: Evolution of the BAT photon index 15-150 keV (black points) for GRB050219a during segments 1-5 (see text for details). The red triangle indicates the 0.2-10 keV XRT photon index during the steep early decline phase of the burst. The BAT and XRT errors are 90% confidence limits on the spectral fit.
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In the text

$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics[angle=270,width=7cm]{44... ...box{8.8cm}{!}{\includegraphics[angle=270,width=7cm]{4457fig8b.eps}} \end{figure}$ Figure 8: Timeline showing the LrPD count-rate during the slew, settling and early pointing phase observations of GRB050219a. The object enters the XRT field of view ${\approx }82$ s after the BAT trigger. Observations at $t_{\rm b}+86$ s onwards are less than 5 arcmin from the final pointing and are well within the XRT field of view ( $24\times 24$ arcmin squared).
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In the text

$\begin{figure} \par {\includegraphics[angle=270,width=8.5cm]{4457fig9.eps} }\end{figure}$ Figure 9: The XRT 0.2-10.0 keV decay light-curve for GRB050219a. Colours indicate LrPD data (blue), IM data (magenta), WT data (red), and PC mode data (green). The best-fit broken power-law fit to the decay curve after 100 s has a decay slope $\alpha _{1}=3.17^{+0.24}_{-0.16}$ at early times flattening to a slope of $\alpha _{2}=0.75^{+0.09}_{-0.07}$ after 332⁺²⁶_-22 s (solid line), $\chi ^{2}=74.6$ for 36 d.o.f. We also show (dashed line) the result of fitting the function $f_{\nu }(t)\propto (t-t_{\rm a})^{-\alpha }$ , where $t_{\rm a}$ represents the onset of the afterglow, with a best-fit slope $\alpha =1.10^{+0.09}_{-0.08}$ and $t_{\rm a}=100.7^{+2.8}_{-4.0}$ s. This model is a poor approximation to the late time data (t>5000 s). We note that the early LrPD and IM data suggest a possible flare at early times, or alternatively, may indicate the onset of the afterglow emission.
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In the text

$\begin{figure} \par {\includegraphics[angle=270,width=8.3cm]{4457fig10.eps} }\end{figure}$ Figure 10: BAT-XRT light-curve for GRB050219a (0.2-10 keV, see text for details). Note that the early steep decline in the XRT data does not appear to join up smoothly with the late time BAT data.
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In the text

$\begin{figure} \par {\includegraphics[angle=270,width=8.5cm]{4457fig11.eps} }\end{figure}$ Figure 11: Combined power-law fit to the BAT (20-150 keV) and XRT (0.2-10 keV) spectra of GRB050219a. Inset: 68.3%, 90%, 95.4% and 99% confidence contours indicating the relative Photon indices for BAT and XRT in a combined fit to the BAT and XRT spectra of GRB050219a. The data are inconsistent with a single power-law fit to the BAT and XRT spectra at greater than 99% confidence.
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In the text

$\begin{figure} \par\includegraphics[angle=270,width=8cm]{4457fig1.eps} \end{figure}$	Figure 1: 15-350 keV mask-weighted (i.e. background subtracted) BAT lightcurve of GRB050126. The x-axis indicates the elapsed time in seconds from the BAT rate trigger.
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$\begin{figure} \par {\includegraphics[angle=270,width=8.3cm]{4457fig3.eps} }\end{figure}$	Figure 3: BAT-XRT decay light-curve for GRB050126 (0.2-10 keV, see text for details). Note that the early steep decline phase in the XRT light-curve joins smoothly with the late-time BAT data.
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$\begin{figure} \par {\includegraphics[angle=270,width=8cm]{4457fig5.eps} }\end{figure}$	Figure 5: 15-350 keV mask-weighted BAT lightcurve of GRB050219a. The dotted lines (segments 1-5) indicate the time-slices used for the BAT spectral evolution analysis. Zero represents the BAT rate trigger time.
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$\begin{figure} \par {\includegraphics[angle=270,width=8cm]{4457fig6.eps} }\end{figure}$	Figure 6: Cross-correlation functions indicating the interband delays in 4 BAT channels for GRB050219a. The light-curves are highly correlated with the hardest bands leading the softer bands by $0.7\pm 0.1$ s (band 4 - band 3), $1.3\pm 0.1$ s (band 3 - band 2), and $2.7\pm 0.1$ s (band 2 - band 1) respectively.
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$\begin{figure} \par {\includegraphics[angle=270,width=8cm]{4457fig7.eps} } \end{figure}$	Figure 7: Evolution of the BAT photon index 15-150 keV (black points) for GRB050219a during segments 1-5 (see text for details). The red triangle indicates the 0.2-10 keV XRT photon index during the steep early decline phase of the burst. The BAT and XRT errors are 90% confidence limits on the spectral fit.
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$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics[angle=270,width=7cm]{44... ...box{8.8cm}{!}{\includegraphics[angle=270,width=7cm]{4457fig8b.eps}} \end{figure}$	Figure 8: Timeline showing the LrPD count-rate during the slew, settling and early pointing phase observations of GRB050219a. The object enters the XRT field of view ${\approx }82$ s after the BAT trigger. Observations at $t_{\rm b}+86$ s onwards are less than 5 arcmin from the final pointing and are well within the XRT field of view ( $24\times 24$ arcmin squared).
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$\begin{figure} \par {\includegraphics[angle=270,width=8.3cm]{4457fig10.eps} }\end{figure}$	Figure 10: BAT-XRT light-curve for GRB050219a (0.2-10 keV, see text for details). Note that the early steep decline in the XRT data does not appear to join up smoothly with the late time BAT data.
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$\begin{figure} \par {\includegraphics[angle=270,width=8.5cm]{4457fig11.eps} }\end{figure}$	Figure 11: Combined power-law fit to the BAT (20-150 keV) and XRT (0.2-10 keV) spectra of GRB050219a. Inset: 68.3%, 90%, 95.4% and 99% confidence contours indicating the relative Photon indices for BAT and XRT in a combined fit to the BAT and XRT spectra of GRB050219a. The data are inconsistent with a single power-law fit to the BAT and XRT spectra at greater than 99% confidence.
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