Astronomy & Astrophysics

All Figures

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{Fk101_f1.ps} \end{figure}$ Figure 1: Vertical structure of the atmosphere of HD 259458b as a function of the temperature of the upper atmosphere (Model A). At the top of the thermosphere, the exobase is the critical level where the mean free path is equal to the distance to the Roche lobe. For high temperatures, the exobase reaches the Roche lobe; this leads to a geometrical blow-off.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{Fk101_f2.ps}\par \end{figure}$ Figure 2: Shape of the exobase and the corresponding escape rate (Model A, $T_{\rm up}=11~100$ K). Light grey is for the large escape rates (10¹⁰ g s^-1 str^-1) and black is for the small escape rates (< $5\times 10^9$ g s^-1 str^-1). The star is on the X-axis toward positive coordinates. The escape rate is the largest toward the star and in the opposite direction.
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{Fk101_f3.ps} \end{figure}$ Figure 3: Escape flux and life time of HD 209458b as a function of $T_{\rm up}$ . The results from various models show the uncertainty due to the lack of constraint on the densities at the thermobase. a) shows the escape flux of H I (long dashed) and H₂(short dashed) in the Model A, and the total escape flux (solid lines) for models A, B and C. For the Model A, the total escape flux from an isolated planet (without tidal forces) is plotted with the dot-dashed line. The tidal forces increase the evaporation rate by one to two orders of magnitude. b) shows the planet life time. A first estimate is obtained from the instantaneous escape flux for Model A (t₁, dashed line). Taking into account the planet's mass decrease with time, we find shorter life times (t₂, solid lines).
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{Fk101_f4.ps} \end{figure}$ Figure 4: Upper atmosphere temperature estimated from the energy balance as a function of the orbital distance of a 0.69 $M_{\rm Jup}$ planet. Theinput energy is $2.7 \times (d/1~{\rm AU})^{-2}$ erg cm^-2 s^-1. Below 0.04 AU, the temperature decreases because the large escape rate cools downthe thermosphere.
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In the text

$\begin{figure} \par\includegraphics[angle=90,width=8cm]{Fk101_f5.ps} \end{figure}$ Figure 5: Contour plot of the planet life time ( $\log _{10} t_2/{\rm year}$ ) as a function of the mass and orbital distance (Model A). The temperature is obtained from the energy balance and is varying with time. We obtain similar numerical estimates and contour plots for Model B and C. The squares show the positions of detected planets. OGLE-TR-56b is at the upper left conner. HD 209458b is shown by a circle. HD 49674b, HD 46375b, HD 76700b, and HD 83443b (triangles) have life time of about 10⁹ years. These planets must have lost a large fraction of their hydrogen and might be remnants of former hot Jupiters.
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{Fk101_f1.ps} \end{figure}$	Figure 1: Vertical structure of the atmosphere of HD 259458b as a function of the temperature of the upper atmosphere (Model A). At the top of the thermosphere, the exobase is the critical level where the mean free path is equal to the distance to the Roche lobe. For high temperatures, the exobase reaches the Roche lobe; this leads to a geometrical blow-off.
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$\begin{figure} \par\includegraphics[width=8cm,clip]{Fk101_f2.ps}\par \end{figure}$	Figure 2: Shape of the exobase and the corresponding escape rate (Model A, $T_{\rm up}=11~100$ K). Light grey is for the large escape rates (10¹⁰ g s^-1 str^-1) and black is for the small escape rates (< $5\times 10^9$ g s^-1 str^-1). The star is on the X-axis toward positive coordinates. The escape rate is the largest toward the star and in the opposite direction.
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$\begin{figure} \par\includegraphics[width=8.5cm,clip]{Fk101_f4.ps} \end{figure}$	Figure 4: Upper atmosphere temperature estimated from the energy balance as a function of the orbital distance of a 0.69 $M_{\rm Jup}$ planet. Theinput energy is $2.7 \times (d/1~{\rm AU})^{-2}$ erg cm^-2 s^-1. Below 0.04 AU, the temperature decreases because the large escape rate cools downthe thermosphere.
Open with DEXTER