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Description
About 20% of the >1000 known exoplanets are Jupiter analogs orbiting very close to their parent stars. It is still under debate to what detectable level such hot Jupiters possibly affect the activity of the host stars through tidal or magnetic star-planet interaction. In this paper we report on an 87ks Chandra observation of the hot Jupiter hosting star WASP-18. This system is composed of an F6 type star and a hot Jupiter of mass 10.4M_Jup_ orbiting in less than 20hr around the parent star. On the basis of an isochrone fitting, WASP-18 is thought to be 600Myr old and within the range of uncertainty of 0.5-2Gyr. The star is not detected in X-rays down to a luminosity limit of 4x10^26^erg/s, which is more than two orders of magnitude lower than expected for a star of this age and mass. This value proves an unusual lack of activity for a star with an estimated age around 600Myr. We argue that the massive planet can play a crucial role in disrupting the stellar magnetic dynamo created within its thin convective layers. Other additional 212 X-ray sources are detected in the Chandra image. We list them and briefly discuss their nature.
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