THREE-DIMENSIONAL GAS DYNAMIC SIMULATION OF THE INTERACTION BETWEEN THE EXOPLANET WASP-12b AND ITS HOST STAR

• Published in: The Astrophysical journal Vol. 764; no. 1; pp. 1 - 5
• Main Authors: BISIKALO, D, KAYGORODOV, P, Ionov, D, SHEMATOVICH, V, Lammer, H, Fossati, L
• Format: Journal Article
• Language: English
• Published: United States 10.02.2013
• Subjects: ANGULAR MOMENTUM; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASYMMETRY; ATMOSPHERES; AXIAL SYMMETRY; Deflection; Dynamical systems; Dynamics; Extrasolar planets; Gas dynamics; HYDRODYNAMICS; INTERACTIONS; MAGNETIC FIELDS; MATTER; NUMERICAL SOLUTION; Outflow; Overfilling; PLANETS; PLASMA; RADIANT HEAT TRANSFER; ROCHE EQUIPOTENTIALS; SHOCK WAVES; SIMULATION; STEADY-STATE CONDITIONS; STELLAR WINDS; TELESCOPES; Three dimensional; THREE-DIMENSIONAL CALCULATIONS
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/764/1/19

Hubble Space Telescope transit observations in the near-UV performed in 2009 made WASP-12b one of the most "mysterious" exoplanets; the system presents an early ingress, which can be explained by the presence of optically thick matter located ahead of the planet at a distance of ~4-5 planet radii. This work follows previous attempts to explain this asymmetry with an exospheric outflow or a bow shock, induced by a planetary magnetic field, and provides a numerical solution of the early ingress, though we did not perform any radiative transfer calculation. We performed pure 3D gas dynamic simulations of the plasma interaction between WASP-12b and its host star and describe the flow pattern in the system. In particular, we show that the overfilling of the planet's Roche lobe leads to a noticeable outflow from the upper atmosphere in the direction of the L sub(1) and L sub(2) points. Due to the conservation of the angular momentum, the flow to the L sub(1) point is deflected in the direction of the planet's orbital motion, while the flow toward L sub(2) is deflected in the opposite direction, resulting in a non-axisymmetric envelope, surrounding the planet. The supersonic motion of the planet inside the stellar wind leads to the formation of a bow shock with a complex shape. The existence of the bow shock slows down the outflow through the L sub(1) and L sub(2) points, allowing us to consider a long-living flow structure that is in the steady state.