3D Modeling of absorption by various species for hot jupiter HD209458b

Abstract

ABSTRACT The absorption of stellar radiation observed at transits of HD209458b in resonant lines of OI and CII has not yet been satisfactorily modeled. In our previous 2D simulations we have shown that hydrogen-dominated upper atmosphere of HD209458b, heated by XUV radiation, expands supersonically beyond the Roche lobe and drags heavier species along with it. Assuming solar abundances, OI and CII particles accelerated by tidal forces to velocities up to 50 km/s 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 remained to which extent the spiraling of escaping planetary material and actually achieved velocity may influence the conclusions made on basis of 2D modeling. In the present paper we apply for the first time in studies of HD209458b a global 3D hydrodynamic multi-fluid model. The results confirm our previous findings that the velocity of the planetary flow is sufficiently high to match the widths of OI and CII resonant lines. To match absorption in those lines, including HI, with observations, the mass loss rate of HD209458b should be about 2.5·1011 g/s 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 MgII and SiIII lines requires at least 10 times lower abundances of these elements than the Solar values.