* Astronomy

Title: Spitzer Infrared Observations and Independent Validation of the Transiting Super-Earth CoRoT-7b
Authors: Francois Fressin, Guillermo Torres, Frederic Pont, Heather A. Knutson, David Charbonneau, Tsevi Mazeh, Suzanne Aigrain, Malcolm Fridlund, Christopher E. Henze, Tristan Guillot, Heike Rauer

The detection and characterization of the first transiting super-Earth, CoRoT-7 b, has required an unprecedented effort in terms of telescope time and analysis. Although the star does display a radial velocity signal at the period of the planet, this has been difficult to disentangle from the intrinsic stellar variability, and pinning down the velocity amplitude has been very challenging. As a result, the precise value of the mass of the planet - and even the extent to which it can be considered to be confirmed - have been debated in the recent literature, with six mass measurements published so far based on the same spectroscopic observations, ranging from about 2 to 8 Earth masses. Here we report on an independent validation of the planet discovery, using one of the fundamental properties of a transit signal: its achromaticity. We observed four transits of CoRoT-7 b with Spitzer, in order to determine whether the depth of the transit signal in the near-infrared is consistent with that observed in the CoRoT bandpass, as expected for a planet. We detected the transit and found an average depth of 0.426 ±0.115 mmag at 4.5 {\mu}m, which is in good agreement with the depth of 0.350 ±0.011 mmag found by CoRoT. These observations place important constraints on the kinds of astrophysical false positives that could mimic the signal. Combining this with additional constraints reported earlier, we performed an exhaustive exploration of possible blends scenarios for CoRoT-7 b using the BLENDER technique. We are able to rule out the vast majority of false positives, and the remaining ones are found to be much less likely than a true transiting planet. We thus validate CoRoT-7 b as a bona-fide planet with a very high degree of confidence, independently of any radial-velocity information. Our Spitzer observations have additionally allowed us to significantly improve the ephemeris of the planet.

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Title: The extreme physical properties of the CoRoT-7b super-Earth
Authors: A. Léger, O. Grasset, B. Fegley, F. Codron, A. F. Albarede, P. Barge, R. Barnes, P. Cance, S. Carpy, F. Catalano, C. Cavarroc, O. Demangeon, S. Ferraz-Mello, P. Gabor, J.-M. Griessmeier, J. Leibacher, G. Libourel, A-S. Maurin, S.N. Raymond, D. Rouan, B. Samuel, L. Schaefer, J. Schneider, P. A. Schuller, F. Selsis, C. Sotin

The search for rocky exoplanets plays an important role in our quest for extra-terrestrial life. Here, we discuss the extreme physical properties possible for the first characterized rocky super-Earth, CoRoT-7b (R_pl = 1.58 ± 0.10 R_Earth, Mpl = 6.9 ± 1.2 M_Earth). It is extremely close to its star (a = 0.0171 AU = 4.48 R_st), with its spin and orbital rotation likely synchronised. The comparison of its location in the (Mpl, Rpl) plane with the predictions of planetary models for different compositions points to an Earth-like composition, even if the error bars of the measured quantities and the partial degeneracy of the models prevent a definitive conclusion. The proximity to its star provides an additional constraint on the model. It implies a high extreme-UV flux and particle wind, and the corresponding efficient erosion of the planetary atmosphere especially for volatile species including water. Consequently, we make the working hypothesis that the planet is rocky with no volatiles in its atmosphere, and derive the physical properties that result. As a consequence, the atmosphere is made of rocky vapours with a very low pressure (P \leq 1.5 Pa), no cloud can be sustained, and no thermalisation of the planetary is expected. The dayside is very hot (2474 \leq 71 K at the sub-stellar point) while the nightside is very cold (50 to 75 K). The sub-stellar point is as hot as the tungsten filament of an incandescent bulb, resulting in the melting and distillation of silicate rocks and the formation of a lava ocean. These possible features of CoRoT-7b could be common to many small and hot planets, including the recently discovered Kepler-10b. They define a new class of objects that we propose to name "Lava-ocean planets".

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The planet, tagged CoRoT-7b, first hit the headlines last September when a team of astronomers confirmed the orb as the smallest exoplanet yet found. Its diameter is roughly 1.7 times that of Earth. Based on its size and mass, its density is similar to Earth's, indicating that it is a rocky Earth-like orb.
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First Earth-like planet spotted outside solar system likely a volcanic wasteland

When scientists confirmed in October that they had detected the first rocky planet outside our solar system, it advanced the longtime quest to find an Earth-like planet hospitable to life. The rocky planet CoRoT-7 b is, however, a forbidding place. If its orbit is not almost perfectly circular, then the planet might be undergoing continuous, fierce volcanic eruptions, according to information presented at the American Astronomical Society meeting.
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