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The recently installed Adaptive Optics system NAOS now offers diffraction limited images at the VLT. Together with the CONICA camera, NAOS provides the possibility to perform high dynamical range observations in the near IR domain. We present here NAOS-CONICA (hereafter NACO) capabilities as well as the first images of binaries obtained during NACO commissioning.
Here we present the installation and successful commissioning of an L'-band Annular Groove Phase Mask (AGPM) coronagraph on VLT/NACO. The AGPM is a vector vortex coronagraph made from diamond subwavelength gratings tuned to the L' band. The vector vortex coronagraph enables high contrast imaging at very small inner working angle (here 0″.09, the diffraction limit of the VLT at L'), potentially being the key to a new parameter space. During technical and science verification runs, we discovered a late-type companion at two beamwidths from an F0V star (Mawet et al. 2013), and imaged the inner regions of β Pictoris down to the previously unexplored projected radius of 1.75 AU. The circumstellar disk was also resolved from ≃ 1″ to 5″ (see J. Milli et al., these proceedings). These results showcase the potential of the NACO L-band AGPM over a wide range of spatial scales.
Over the past decade, a growing number of deep imaging surveys have started to provide meaningful constraints on the population of extrasolar giant planets at large orbital separation. Primary targets for these surveys have been carefully selected based on their age, distance and spectral type, and often on their membership to young nearby associations where all stars share common kinematics, photometric and spectroscopic properties. The next step is a wider statistical analysis of the frequency and properties of low mass companions as a function of stellar mass and orbital separation. In late 2009, we initiated a coordinated European Large Program using angular differential imaging in the H band (1.66 μm) with NaCo at the VLT. Our aim is to provide a comprehensive and statistically significant study of the occurrence of extrasolar giant planets and brown dwarfs at large (5-500 AU) orbital separation around ~150 young, nearby stars, a large fraction of which have never been observed at very deep contrast. The survey has now been completed and we present the data analysis and detection limits for the observed sample, for which we reach the planetary-mass domain at separations of ≳50 AU on average. We also present the results of the statistical analysis that has been performed over the 75 targets newly observed at high-contrast. We discuss the details of the statistical analysis and the physical constraints that our survey provides for the frequency and formation scenario of planetary mass companions at large separation.
We report the detection of multi-armed spirals in the environment of HD 100546 using NICI at Gemini South in the Ks band. These data feature a better angular resolution and higher contrast than previous HST images, which allows to resolve the former known spiral into a multiple pattern. An analytic model with a gravitational perturber is used to fit the spiral pattern. We derived limit of detections which set constraints on the discovered forming planet.
Although slow and dissipative, sputtered thin-film shape-memory alloys like equiatomic titanium-nickel can exert a large ohmically-excited force·displacement product when deployed in photolithographically micromachined actuators. They give energy densities far exceeding those typically produced by competing microactuator materials , and their size can probably be scaled down to the nanometer range (where the benefits of high surface to volume ratio are best exploited for speed and efficiency). But a large, energetic, and resettable actuation stroke is possible only if some agency has imparted a non-trivial initial plastic strain, of between one and five percent, to the martensite phase. Is not always obvious how this strain is to be achieved when discrete mechanical manipulation of the active element is difficult. Furthermore, for cyclic actuation, a resetting-force that periodically re-deforms the martensite during the cooling interval must arise naturally from mechanical elements in the design. Here, several methods responding these requirements are discussed in relation to various kinematic themes.
Atomic hydrogen escaping from the extrasolar giant planet HD 209458b provides
the largest observational signature ever detected for an extrasolar planet
atmosphere. In fact, the upper atmosphere of this planet is evaporating.
Observational evidences and interpretations coming from various models are
reviewed. Implications for exoplanetology are discussed.