CoRoT's first seven planets: An overview

The up to 150 day uninterrupted high-precision photometry of about 100000 stars - provided so far by the exoplanet channel of the CoRoT space telescope - gave a new perspective on the planet population of our galactic neighbourhood. The seven planets with very accurate parameters widen the range of known planet properties in almost any respect. Giant planets have been detected at low metallicity, rapidly rotating and active, spotted stars. CoRoT-3 populated the brown dwarf desert and closed the gap of measured physical properties between standard giant planets and very low mass stars. CoRoT extended the known range of planet masses down to 5 Earth masses and up to 21 Jupiter masses, the radii to less than 2 Earth radii and up to the most inflated hot Jupiter found so far, and the periods of planets discovered by transits to 9 days. Two CoRoT planets have host stars with the lowest content of heavy elements known to show a transit hinting towards a different planet-host-star-metallicity relation then the one found by radial-velocity search programs. Finally the properties of the CoRoT-7b prove that terrestrial planets with a density close to Earth exist outside the Solar System. The detection of the secondary transit of CoRoT-1 at the $10^{-5}$-level and the very clear detection of the 1.7 Earth radii of CoRoT-7b at $3.5 10^{-4}$ relative flux are promising evidence of CoRoT being able to detect even smaller, Earth sized planets.Comment: 8 pages, 19 figures and 3 table

PyTranSpot\texttt{PyTranSpot} - A tool for multiband light curve modeling of planetary transits and stellar spots

Several studies have shown that stellar activity features, such as occulted and non-occulted starspots, can affect the measurement of transit parameters biasing studies of transit timing variations and transmission spectra. We present $\texttt{PyTranSpot}$, which we designed to model multiband transit light curves showing starspot anomalies, inferring both transit and spot parameters. The code follows a pixellation approach to model the star with its corresponding limb darkening, spots, and transiting planet on a two dimensional Cartesian coordinate grid. We combine $\texttt{PyTranSpot}$ with an MCMC framework to study and derive exoplanet transmission spectra, which provides statistically robust values for the physical properties and uncertainties of a transiting star-planet system. We validate $\texttt{PyTranSpot}$'s performance by analyzing eleven synthetic light curves of four different star-planet systems and 20 transit light curves of the well-studied WASP-41b system. We also investigate the impact of starspots on transit parameters and derive wavelength dependent transit depth values for WASP-41b covering a range of 6200-9200 $\AA$, indicating a flat transmission spectrum.Comment: 17 pages, 22 figures; accepted for publication in Astronomy & Astrophysic

Coronal properties of planet-bearing stars

Do extrasolar planets affect the activity of their host stars? Indications for chromospheric activity enhancement have been found for a handful of targets, but in the X-ray regime, conclusive observational evidence is still missing. We want to establish a sound observational basis to confirm or reject major effects of Star-Planet Interactions (SPI) in stellar X-ray emissions. We therefore conduct a statistical analysis of stellar X-ray activity of all known planet-bearing stars within 30pc distance for dependencies on planetary parameters such as mass and semimajor axis. We find that in our sample, there are no significant correlations of X-ray luminosity or the activity indicator L_X/L_bol with planetary parameters which cannot be explained by selection effects. Coronal SPI seems to be a phenomenon which might only manifest itself as a strong effect for a few individual targets, but not to have a major effect on planet-bearing stars in general.Comment: accepted by A&

On the protection of extrasolar Earth-like planets around K/M stars against galactic cosmic rays

Previous studies have shown that extrasolar Earth-like planets in close-in habitable zones around M-stars are weakly protected against galactic cosmic rays (GCRs), leading to a strongly increased particle flux to the top of the planetary atmosphere. Two main effects were held responsible for the weak shielding of such an exoplanet: (a) For a close-in planet, the planetary magnetic moment is strongly reduced by tidal locking. Therefore, such a close-in extrasolar planet is not protected by an extended magnetosphere. (b) The small orbital distance of the planet exposes it to a much denser stellar wind than that prevailing at larger orbital distances. This dense stellar wind leads to additional compression of the magnetosphere, which can further reduce the shielding efficiency against GCRs. In this work, we analyse and compare the effect of (a) and (b), showing that the stellar wind variation with orbital distance has little influence on the cosmic ray shielding. Instead, the weak shielding of M star planets can be attributed to their small magnetic moment. We further analyse how the planetary mass and composition influence the planetary magnetic moment, and thus modify the cosmic ray shielding efficiency. We show that more massive planets are not necessarily better protected against galactic cosmic rays, but that the planetary bulk composition can play an important role.Comment: 7 figure

Escaping Particle fluxes in the atmospheres of close-in exoplanets: I. model of hydrogen

A multi-fluid model for an atomic hydrogen-proton mixture in the upper atmosphere of extrosolar planet is presented when the continuity and momentum equations of each component have been already solved with an energy equation. The particle number density, the temperature distribution and the structure of velocity can be found by means of the model. We chose two special objects, HD 209458b and HD 189733b, as discussion samples and the conclusion is that their mass loss rates predicted by the model are in accordance with those of observation. The most important physical process in coupling each component is charge exchange which tightly couples atomic hydrogen with protons. Most of the hydrogen escaping from hot Jupiters is protons, especially in young star-planet system. We found that the single-fluid model can describe the escape of particles when the mass loss rate is higher than a few times $10^{9}$ g/s while below $10^{9}$ g/s the multi-fluid model is more suitable for it due to the decoupling of particles. We found that the predicted mass loss rates of HD 189733b with the assumption of energy-limit are a factor of 10 larger than that calculated by our models due to the high ionization degree. For the ionized wind which is almost compose of protons, the assumption of energy-limit is no longer effective. We fitted the mass loss rates of the ionized wind as a function of $F_{UV}$ by calculating the variation of the mass loss rates with UV fluxes.Comment: 35 pages, 6 figures, submitted to Ap

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

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 (3.5 sigma) X-ray detection of CoRoT-7. We determine a coronal temperature of ca. 3 MK and an X-ray luminosity of 3*10^28 erg/s. The level of XUV irradiation on CoRoT-7b amounts to ca. 37000 erg/cm^2/s. 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 and has lost ca. 4-10 earth masses in total.Comment: 5 pages, accepted for publication by Astronomy & Astrophysic

Aortomonoiliac Endografting after Failed Endovascular Aneurysm Repair: Indications and Long-term Results

AbstractObjectivesTo present long-term results of endoleak/endograft migration treatment by aortomonoiliac (AMI) endografting after failed endovascular aneurysm repair (EVAR) of infrarenal abdominal aortic aneurysms.DesignPost hoc analysis of a prospectively gathered database at a tertiary care university hospital.Materials and methodsFrom March 1995 to November 2010, 23 patients were identified who underwent modification into AMI configuration after failed elective EVAR. Major causes for modification were type I (with/without endograft migration) or type III endoleaks with aneurysm expansion. An average increase in aneurysm size of 1.6 cm (range: −1.5 to 10.5 cm) since initial aneurysm treatment was observed. Interventional outcomes and long-term results were recorded for analysis.ResultsTechnical success rate of AMI endografting was 95.65% (n = 22). All except two endoleaks could be successfully sealed with this manoeuvre (94.44%). Median time to modification was 5.3 years (interquartile range Q1–Q3: 1.3–9.3 years). No intra-operative conversion to open surgery was necessary and mortality was 0%. Median follow-up was 44 months (interquartile range Q1–Q3: 17–69 months).ConclusionsTreatment of graft-related endoleaks/endograft migration by AMI endografting after failed EVAR represents a safe and feasible procedure. This approach broadens the minimal invasive opportunities of aneurysm treatment, and open surgical conversion may be avoided except in selected patients