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The formation of massive stars remains one of the most intriguing questions in astrophysics today. The main limitations result from the difficulty to obtain direct observational constraints on the formation process itself. In this context, the Carina High-contrast Imaging Project of massive Stars (CHIPS) aims to observe all 80+ O stars in the Carina nebula using the new VLT 2nd-generation extreme-AO instrument SPHERE. This instrument offers unprecedented imaging contrast allowing us to detect the faintest companions around massive stars. These novel observational constraints will help to discriminate between the different formation scenarios by comparing their predictions for companion statistics and properties.
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.
Imaging debris discs in the L′-band (3.8 μm) is a difficult task. Quasi-static speckles from imperfect optics prevail below 1″ whereas background emission is the dominant noise source beyond that separation and is much larger than at shorter wavelengths. We demonstrate here the potential of the newly commissioned AGPM coronograph on VLT/NaCo combined with advanced star and sky subtraction technique based on Principal Component Analysis, and we analyze the morphology of the β Pictoris disc.
The ALADDIN concept is an integrated Antarctic-based L-band experiment whose purpose is to demonstrate nulling interferometry and to prepare the DARWIN mission. Because of their privileged location, the relatively modest collectors (1 m) and baseline (up to 40 m) are sufficient to achieve a sensitivity (in terms of detectable zodi levels) which is about twice better than that of a nulling instrument on a large interferometer (such as GENIE at the VLTI), and to reach the 20-zodi threshold value identified to carry out the DARWIN precursor science. These numbers are based on a preliminary design study by Alcatel Alenia Space and were obtained using the same simulation software as the one employed for GENIE. The integrated design enables top-level optimization and full access to the light collectors for the duration of the experiment, while reducing the complexity of the nulling breadboard.
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