Thursday, February 12, 2015

How Fast do Hot Jupiters Evaporate?

High-energy irradiation and mass loss rates of hot Jupiters in the solar neighborhood


Salz et al


Giant gas planets in close proximity to their host stars experience strong irradiation. In extreme cases photoevaporation causes a transonic, planetary wind and the persistent mass loss can possibly affect the planetary evolution. We have identified nine hot Jupiter systems in the vicinity of the Sun, in which expanded planetary atmospheres should be detectable through Lyman alpha transit spectroscopy according to predictions. We use X-ray observations with Chandra and XMM-Newton of seven of these targets to derive the high-energy irradiation level of the planetary atmospheres and the resulting mass loss rates. We further derive improved Lyman alpha luminosity estimates for the host stars including interstellar absorption. According to our estimates WASP-80 b, WASP-77 b, and WASP-43 b experience the strongest mass loss rates, exceeding the mass loss rate of HD 209458 b, where an expanded atmosphere has been confirmed. Furthermore, seven out of nine targets might be amenable to Lyman alpha transit spectroscopy. Finally, we check the possibility of angular momentum transfer from the hot Jupiters to the host stars in the three binary systems among our sample, but find only weak indications for increased stellar rotation periods of WASP-77 and HAT-P-20.

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