Astronomy & Astrophysics

All Figures

$\begin{figure} \par\includegraphics[width=7.5cm,clip]{0027f1.ps} \end{figure}$ Figure 1: Upper panel: light curve (10 ks) of the flare on Proxima Centauri on 12 August 2001 as detected with the XMM-Newton EPIC-PN detector in the 0.15-10 keV band. The flare can be segmented into six phases, two rising (R1, R2) and four decay ones (D1-D4), bounded by the vertical dashed lines. The solid lines mark the decay trends. Time t=0 corresponds to 17:00 UT of 12 August 2001. Lower panel: hardness ratio (ratio of 1-4.5 keV to 0.4-1 keV count rates) in the same time interval as the light curve. Time resolution is 300 s.
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In the text

$\begin{figure} \par\includegraphics[width=7.5cm,clip]{0027f2.ps} \end{figure}$ Figure 2: Temperature and emission measure diagrams during the flare: the upper panel shows the density-temperature (n-T) diagram of the dominating component of the 2-T fitting, where EM^1/2 has been used as a proxy for the density. The dashed line marks the evolution of the values and the end point of each phase is labelled. The lower panels show the evolution of the temperature and emission measure separately. Dashed lines as in Fig. 1.
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In the text

$\begin{figure} \par\includegraphics[width=14.6cm,clip]{0027f3.ps} \end{figure}$ Figure 3: Left: fitting the observed light curve ( data points) of the phases R1 and D1 with hydrodynamic simulations of a single flaring loop. The figure shows the light curves obtained from a loop with half-length 10¹⁰ cm heated at the footpoints ( solid line) and at the apex ( dotted line), from a loop with half-length $0.7 \times 10^{10}$ cm heated at the footpoints ( dashed line), and from a loop with half-length $1.6 \times 10^{10}$ cm heated at the apex ( dashed-dotted line). Right: corresponding paths in the EM^1/2-T diagram, obtained from fitting the model and the observed spectra with isothermal models (only the first five data points are shown).
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In the text

$\begin{figure} \par\includegraphics[width=7.2cm,clip]{0027f4.ps} \end{figure}$ Figure 4: Fitting the observed light curve ( data points) of the flare phase D2 with a decaying heating switched on at the end of the heating pulse at the footpoints: distributed uniformly in the loop with initial intensity 1.2 erg cm^-3 s^-1 ( solid line), distributed uniformly in the loop with initial intensity 0.75 erg cm^-3 s^-1 ( dotted line), and deposited at the footpoints (15 erg cm^-3 s^-1, dashed line). Data points as in Fig. 3.
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In the text

$\begin{figure} \par\includegraphics[width=6cm,clip]{0027f5.ps} \end{figure}$ Figure 5: Fitting the observed flare light curve ( data points) from phase R1 to D3 with a model consisting of the sum ( solid line) of a footpoint-heated flaring loop with half-length 10¹⁰ cm (with no decaying heating, dotted line), and of a second top-heated flaring loop with half-length $2.5 \times 10^{10}$ cm, ignited at the same time as loop A ( dashed line). The two lower panels show the emission measure and temperature versus time obtained from fitting the model and the observed spectra with isothermal models. Data points as in Figs. 1 and 2.
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In the text

$\begin{figure} \par\includegraphics[width=6cm,clip]{0027f6.ps} \end{figure}$ Figure 6: Fitting the observed flare light curve ( data points) from phase R1 to D3 with a model consisting of the sum ( solid line) of two flaring loop systems with the same half-length and similar heating function: one (loop A, dotted line) is heated 2600 s earlier and 10 times more intensely than the other (loop B, dashed line). A residual heating sustains the decay of both loops. Data points and lower panels as in Fig. 5.
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In the text

$\begin{figure} \par\includegraphics[width=8.4cm,clip]{0027f7.ps} \end{figure}$ Figure 7: Fitting the observed light curve ( data points) of the whole flare including two other flaring loop components. Residuals (data counts minus model counts) are also shown. Data points as in Fig. 3.
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In the text

$\begin{figure} \par\includegraphics[width=14.2cm,clip]{0027f8.ps} \end{figure}$ Figure 8: Sketch of the possible scenario of the flaring loop system on Proxima Centauri scaled to the Bastille Day flare on the sun. The size of Proxima Centauri and the flare loops are on scale.
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In the text

$\begin{figure} \par\includegraphics[width=8.7cm,clip]{0027f9.ps} \end{figure}$ Figure 9: Heating function of best-fit multi-loop model (shown in Fig. 6) of the Prox Cen flare according to our modeling. The main loop A ( black) is heated first ( thick solid line) with a pulse at the footpoints, followed by a lower and gradual decay ( thick dashed line) deposited in the coronal segment of the loop. The arcade of loops B ( grey) is heated later with a heating function similar to that of loop A ( thin solid and dashed lines).
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In the text

$\begin{figure} \par\includegraphics[width=8.1cm,clip]{0027f10.ps} \end{figure}$ Figure 10: Evolution of the temperature, density and velocity along the main flaring loop. Distributions along half of the loop are shown at the labelled times (s). The profiles of the second loop system at their maxima are also shown ( dotted line).
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In the text

$\begin{figure} \par\includegraphics[width=8.2cm,clip]{0027f11.ps} \end{figure}$ Figure 11: Emission measure distributions versus temperature (EM(T)) obtained from hydrodynamic modeling of the flaring loop system, shown in Fig. 6. The distributions are averaged over time intervals corresponding approximately to those of the distributions obtained from data analysis in Paper II (intervals A to D).
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In the text

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{0027f12.ps} \end{figure}$ Figure 12: Spectra ( solid line) synthesized from results of the best-fit hydrodynamic loop model (Fig. 7) integrated over time intervals corresponding approximately to those of the spectra shown in Paper II (intervals A to D). Data are overplotted for comparison.
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In the text

$\begin{figure} \par\includegraphics[width=8.4cm,clip]{0027f7.ps} \end{figure}$	Figure 7: Fitting the observed light curve ( data points) of the whole flare including two other flaring loop components. Residuals (data counts minus model counts) are also shown. Data points as in Fig. 3.
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$\begin{figure} \par\includegraphics[width=14.2cm,clip]{0027f8.ps} \end{figure}$	Figure 8: Sketch of the possible scenario of the flaring loop system on Proxima Centauri scaled to the Bastille Day flare on the sun. The size of Proxima Centauri and the flare loops are on scale.
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$\begin{figure} \par\includegraphics[width=8.1cm,clip]{0027f10.ps} \end{figure}$	Figure 10: Evolution of the temperature, density and velocity along the main flaring loop. Distributions along half of the loop are shown at the labelled times (s). The profiles of the second loop system at their maxima are also shown ( dotted line).
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$\begin{figure} \par\includegraphics[width=8.2cm,clip]{0027f11.ps} \end{figure}$	Figure 11: Emission measure distributions versus temperature (EM(T)) obtained from hydrodynamic modeling of the flaring loop system, shown in Fig. 6. The distributions are averaged over time intervals corresponding approximately to those of the distributions obtained from data analysis in Paper II (intervals A to D).
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$\begin{figure} \par\includegraphics[width=8.8cm,clip]{0027f12.ps} \end{figure}$	Figure 12: Spectra ( solid line) synthesized from results of the best-fit hydrodynamic loop model (Fig. 7) integrated over time intervals corresponding approximately to those of the spectra shown in Paper II (intervals A to D). Data are overplotted for comparison.
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