Exoplanets and Stellar Physics

Abstract:

Context. The CoRoT satellite has recently discovered a hot Jupiter that transits across the disc of a F9 main-sequence star called CoRoT-6 with a period of 8.886 days. Aims. We model the photospheric activity of the star and use the maps of the active regions to study stellar differential rotation and the star-planet interaction. Methods. We apply a maximum entropy spot model to fit the optical modulation as observed by CoRoT during a uninterrupted interval of ~ 140 days. Photospheric active regions are assumed to consist of spots and faculae in a fixed proportion with solar-like contrasts. Results. Individual active regions have lifetimes up to 30-40 days. Most of them form and decay within five active longitudes whose different migration rates are attributed to the stellar differential rotation for which a lower limit of ΔΩ/Ω = 0.12 ± 0.02 is obtained. Several active regions show a maximum of activity at a longitude lagging the subplanetary point by ~ 200° with the probability of a chance occurrence being smaller than 1 percent. Conclusions. Our spot modelling indicates that the photospheric activity of CoRoT-6 could be partially modulated by some kind of star-planet magnetic interaction, while an interaction related to tides is highly unlikely because of the weakness of the tidal force. © 2010 ESO.

Abstract:

We present the results of a design study for an integral field spectrograph as the "back-end" instrument for spectroscopy of exoplanets carried out in the context of the EPICS Phase A study. EPICS is the planet finder imager and spectrograph for the E-ELT. In our study we investigated the feasibility of an image slicer based integral field spectrograph and developed an optical design for the image slicer and the necessary pre-optics, as well as the spectrograph optics. We present a detailed analysis of the optical performance of the design. © 2010 Copyright SPIE - The International Society for Optical Engineering.

Abstract:

HARMONI is a proposed visible and near-infrared integral field spectrograph for the European Extremely Large Telescope. We are exploring the merits of adding a coronagraphic capability to HARMONI, specifically targeted at enabling observations of faint, nearby companions (primarily extra-solar planets) that require high contrast. Although HARMONI is not fed by extreme adaptive optics, we show that substantial contrasts can be achieved by post-processing of the hyperspectral data cube using spectral deconvolution. We make predictions of achievable contrast as a function of coronagraph design, based on realistic models of the telescope's aberrations. © 2010 Copyright SPIE - The International Society for Optical Engineering.

Abstract:

Presently, dedicated instruments at large telescopes (SPHERE for the VLT, GPI for Gemini) are about to discover and explore self-luminous giant planets by direct imaging and spectroscopy. The next generation of 30m-40m ground-based telescopes, the Extremely Large Telescopes (ELTs), have the potential to dramatically enlarge the discovery space towards older giant planets seen in reflected light and ultimately even a small number of rocky planets. EPICS is a proposed instrument for the European ELT, dedicated to the detection and characterization of Exoplanets by direct imaging, spectroscopy and polarimetry. ESO completed a phase-A study for EPICS with a large European consortium which - by simulations and demonstration experiments - investigated state-of-the-art diffraction and speckle suppression techniques to deliver highest contrasts. The paper presents the instrument concept and analysis as well as its main innovations and science capabilities. EPICS is capable of discovering hundreds of giant planets, and dozens of lower mass planets down to the rocky planets domain. © 2010 Copyright SPIE - The International Society for Optical Engineering.