The high-energy environment in the super-Earth system CoRoT-7

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2012

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High-energy irradiation of exoplanets has been identified to be a key influence on the stability of these planets' atmospheres. So far, irradiation-driven mass-loss has been observed only in two Hot Jupiters, and the observational data remain even more sparse in the super-Earth regime. We present an investigation of the high-energy emission in the CoRoT-7 system, which hosts the first known transiting super-Earth. To characterize the high-energy XUV radiation field into which the rocky planets CoRoT-7b and CoRoT-7c are immersed, we analyzed a 25 ks XMM-Newton observation of the host star. Our analysis yields the first clear (3.5σ) X-ray detection of CoRoT-7. We determine a coronal temperature of ≈3 MK and an X-ray luminosity of 3 × 10 28 erg s -1. The level of XUV irradiation on CoRoT-7b amounts to ≈37 000 erg cm -2 s -1. Current theories for planetary evaporation can only provide an order-of-magnitude estimate for the planetary mass loss; assuming that CoRoT-7b has formed as a rocky planet, we estimate that CoRoT-7b evaporates at a rate of about 1.3 × 10 11 g s -1 and has lost ≈4-10 earth masses in total. © 2012 ESO.

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Quelldatensatz: oai:www.edit.fis.uni-hamburg.de:publications/2b054512-892a-4417-9d24-2683cdb0b321