SIMBAD references

The absorption of stellar radiation observed at transits of HD 209458b in resonant lines of O I and C II has not yet been satisfactorily modelled. In our previous two-dimensional (2D) simulations, we have shown that the hydrogen-dominated upper atmosphere of HD 209458b, heated by extreme ultraviolet radiation, expands supersonically beyond the Roche lobe and drags heavier species along with it. Assuming solar abundances, O I and C II particles accelerated by tidal forces to velocities up to 50 km s^{-1} should produce the absorption due to Doppler resonance at the level of 6-10 per cent, consistent with the observations. Since the 2D geometry does not take into account the Coriolis force in a planet reference frame, the question remains to what extent the spiralling of escaping planetary material and actually achieved velocity may influence the conclusions made on the basis of 2D modelling. In this paper, we apply for the first time in studies of HD 209458b a global 3D hydrodynamic multifluid model. The results confirm our previous findings that the velocity of the planetary flow is sufficiently high to match the widths of O I and C II resonant lines. To match the absorption in those lines, including H I, with observations, the mass-loss rate of HD 209458b should be about 2.5x10^{11} g s^{-1}, which is 3.5 times larger than that revealed by the 2D model. The other novel finding is that matching of the absorption measured in Mg II and S III lines requires at least 10 times lower abundances of these elements than the solar values.