Exoplanets and Stellar Physics

Abstract:

Presently, dedicated instrument developments 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 expolanets by direct imaging and spectroscopy. ESO recently launched a phase-A study for EPICS with a large European consortium which - by simulations and demonstration experiments - will investigate state-of-the-art diffraction and speckle suppression techniques to deliver highest contrasts. The final result of the study in 2010 will be a conceptual design and a development plan for the instrument. Here we present first results from the phase-A study and discuss the main challenges and science capabilities of EPICS.

Abstract:

Current simulation and experimental investigatory work is going on into the performance of slicer and lenslet IFS designs. The aim of this work is to determine which technology holds the best promise for achieving the highest contrasts with EPICS on the E-ELT. Results from Spectral Deconvolution methods for high contrast detections are presented, both on sky images from AB Dor C observations using SINFONI on the VLT and improvements to the algorithms made through use of EPICS simulation data. Using these simulations, only containing photon and speckle noise, we have been able to detect simulated planets down to a contrast of 1010 located less than 1" from the parent star. The effects of spectral resolution and wavelength range on high contrast observations are discussed. Shortening the wavelength range increases the inner working angle. It is seen that an outer working angle is also reached that decreases with spectral resolution. The limit on the inner working angle can be overcome partly by increasing the wavelength range of the instrument although another inner working angle limit will be reached if a coronagraph is used. The limit of the outer working angle can also be overcome by increasing the spectral resolution of the instrument or possibly by making an IFS that produces an output with a constant spectral resolution, R,instead of constant Δλ.This is still a work in progress.

Abstract:

One of the main science objectives of the European ELT is the direct imaging of extrasolar planets. The large aperture of the telescope has the potential to significantly enlarge the discovery space towards older gas giant exo-planets seen in reflected light. In this paper, we give an overview of the EPICS system design strategy during the phase A study. In order to tackle the critical limitations to high contrast, extensive end-to-end simulations will be developed since the start to test different scenarios and guide the overall design. Keywords: Extremely Large Telescope, high contrast imaging, extrasolar planets, instrumentation, adaptive optics.

Abstract:

Context. The CoRoT space mission routinely provides high-precision photometric measurements of thousands of stars that have been continuously observed for months.Aims. The discovery and characterization of the first very massive transiting planetary companion with a short orbital period is reported.Methods. A series of 34 transits was detected in the CoRoT light curve of an F3V star, observed from May to October 2007 for 152 days. The radius was accurately determined and the mass derived for this new transiting, thanks to the combined analysis of the light curve and complementary ground-based observations: high-precision radial-velocity measurements, on-off photometry, and high signal-to-noise spectroscopic observations.Results. CoRoT-Exo-3b has a radius of 1.01 ± 0.07Jup and transits around its F3-type primary every 4.26 days in a synchronous orbit. Its mass of 21.66 ± 1.0 MJup, density of 26.4 ± 5.6 g cm-3, and surface gravity of log g = 4.72 clearly distinguish it from the regular close-in planet population, making it the most intriguing transiting substellar object discovered so far. Conclusions. With the current data, the nature of CoRoT-Exo-3b is ambiguous, as it could either be a low-mass brown-dwarf or a member of a new class of "superplanets". Its discovery may help constrain the evolution of close-in planets and brown-dwarfs better. Finally, CoRoT-Exo-3b confirms the trend that massive transiting giant planets (M ≥ 4 MJup) are found preferentially around more massive stars than the Sun. © 2008 ESO.

Abstract:

We estimate the dynamical masses of several young (≈10 Myr) massive star clusters in two interacting galaxies, NGC 4038/4039 ("The Antennae") and NGC 1487, under the assumption of virial equilibrium. These are compared with photometric mass estimates. A dynamical mass substantially higher than the photometric estimate could indicate non-virial motion of the stars in the cluster, and potentially lead to cluster disruption. All but one of the Antennae clusters have dynamical and photometric mass estimates which are within a factor ≈ 2 of one another, implying both that standard IMFs provide a good approximation to the IMF of these clusters, and that there is no significant extra-virial motion, as would be expected if they were rapidly dispersing. These results suggest that almost all of the clusters in our sample have survived the gas removal phase as bound or marginally bound objects. But a few targets (two in NGC 1487 and one in the Antennae) have Mdyn estimates which are significantly larger than the photometric mass estimates. At least two of those clusters may be actively in the process of dissolving. The dissolution candidates in both galaxies are amongst the clusters with the lowest pressures/densities measured in our sample. © 2008 WILEY-VCH Verlag GmbH & Co. KGaA.