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

Abstract

The absorption of stellar radiation observed by the HD209458b in resonant lines of OI and CII has not yet been satisfactorily modeled. In our previous 2D simulations we have shown that the hydrogendominated upper atmosphere of HD209458b, heated by XUV radiation, expands supersonically beyond the Roche lobe and drags the 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 mechanism at the level of 6-10%, consistent with the observations. Since the 2D geometry does not take into account the Coriolis force in the planet reference frame, the question remained to which extent the spiraling of the escaping planetary material and its actually achieved velocity may influence the conclusions made on the basis of 2D modeling. In the present paper we apply for the first time in the study of HD209458b a global 3D hydrodynamic multi-fluid model that self-consistently describes the formation and expansion of the escaping planetary wind, affected by the tidal and Coriolis forces, as well as by the surrounding stellar wind. The modeling results confirm our previous findings that the velocity and density of the planetary flow are sufficiently high to produce the absorption in HI, OI, and CII resonant lines at the level close to the in-transit observed values. The novel finding is that the matching of the absorption measured in MgII and SiIII lines requires at least 10 times lower abundances of these elements than the Solar system values.

A Heavy Molecular Weight Atmosphere for the Super-Earth π Men c

“…Unlike the case for π Men c, there is strong evidence that these other exoplanets' atmospheres are H 2 /He-dominated. The transit depth and Doppler velocities reported here are consistent with the C II ions being swept by the stellar wind into a ∼15 R p wide (about the extent of the Roche lobe in the substellar direction, and closer to the planet than the interface between the planetary and stellar winds) tail and accelerated to high velocities, a scenario suggested by 3D models of π Men c and other exoplanets (Shaikhislamov et al 2020a(Shaikhislamov et al , 2020b. We found by means of a simplified phenomenological model of π Men cʼs tail (Appendix B) that the C II measurements can be explained if the planet loses carbon at a rate 10 8 g s −1 , requiring that the atmosphere contains this atom in at least solar abundance.…”

“…(Note: x < 0 in the tail, and the ions are permanently accelerating.) Related accelerations have been predicted by physically motivated 3D models (Ehrenreich et al 2015;Shaikhislamov et al 2020aShaikhislamov et al , 2020b, under the combined effect of gravitational, inertial, and radiative forces. Magnetic interactions with the stellar wind might additionally affect ion acceleration.…”

“…There is observational evidence for HD 209458 b, GJ 436 b and GJ 3470 b that their escaping atmospheres also result in preferential blue absorption (particularly the latter two; Vidal-Madjar et al 2003;Ehrenreich et al 2015;Bourrier et al 2018b). Models considering the 3D geometry of the interacting stellar and planet winds also favor blue absorption, especially when the stellar wind is stronger (Shaikhislamov et al 2020a(Shaikhislamov et al , 2020b and arranges the escaping atoms into a tail trailing the planet. We consider a C II tail to be realistic scenario for π Men c.…”

“…Both HD 209458 b and π Men c transit Sun-like stars and exhibit similar transit depths. Threedimensional models of HD 209458 b (Shaikhislamov et al 2020b) show that its C II absorption signal is explained by carbon in solar abundance. Because the predicted mass-loss rate of HD 209458 b is an order of magnitude higher than for π Men c (a result mainly from its lower density), a reasonable guess is that a ten times solar enrichment for π Men c will result in comparable transit depths.…”

The role of atmospheric outflows in the migration of hot Jupiters

“…The outflow rate depends on the distance to the star, stellar activity, and chemical composition of the planet's atmosphere. Numerical 3D calculations performed by Shaikhislamov et al (2020) and Debrecht et al (2020) showed that, in the case of a relatively weak stellar wind, the matter escaping from the planet can accumulate outside planet's orbit, forming a torus. Hence, it is reasonable to assume that the mass accumulated over time can produce a noticeable gravitational effect on the orbit of the planet.…”