NEAR: New Earths in the Alpha Cen Region (bringing VISIR as a "visiting instrument" to ESO-VLT-UT4)

By adding a dedicated coronagraph, ESO in collaboration with the Breakthrough Initiatives, modifies the Very Large Telescope mid-IR imager (VISIR) to further boost the high dynamic range imaging capability this instru- ment has. After the VISIR upgrade in 2012, where coronagraphic masks were first added to VISIR, it became evident that coronagraphy at a ground-based 8m-class telescope critically needs adaptive optics, even at wavelengths as long as 10μm. For VISIR, a work-horse observatory facility instrument in normal operations, this is ”easiest” achieved by bringing VISIR as a visiting instrument to the ESO-VLT-UT4 having an adaptive M2. This “visit” enables a meaningful search for Earth-like planets in the habitable zone around both α-Cen1,2. Meaningful here means, achieving a contrast of ≈ 10^(-6) within ≈ 0.8arcsec from the star while maintaining basically the normal sensitivity of VISIR. This should allow to detect a planet twice the diameter of Earth. Key components will be a diffractive coronagraphic mask, the annular groove phase mask (AGPM), optimized for the most sensitive spectral band-pass in the N-band, complemented by a sophisticated apodizer at the level of the Lyot stop. For VISIR noise filtering based on fast chopping is required. A novel internal chopper system will be integrated into the cryostat. This chopper is based on the standard technique from early radio astronomy, conceived by the microwave pioneer Robert Dicke in 1946, which was instrumental for the discovery of the 3K radio background

Geoffrey Hunter, Suzette Mayr : Tale

A collaborative project that pairs a writer with an artist to further discourse about contemporary art, “Tale” features Hunter’s images and Mayr’s text, the combination of which blurs the identity of the two. Arsenault playfully interviews both writer and artist, and concludes that their difference is paradoxically bridged by their shared privacy. Biographical notes. 5 bibl. ref

ASSIST ::development of a test-infrastructure for the VLT AO facility

ASSIST - The Adaptive Secondary Setup and Instrument STimulator is a test setup to verify the operation of three elements of the VLT Adaptive Optics Facility, namely the Deformable Secondary Mirror (DSM) and the two AO systems using this DSM, the AO system for the visible light integral field spectrograph MUSE (GALACSI) and the AO system for the IR wide field imager HAWK-I (GRAAL). To support the testing of these elements, ASSIST will provide both an interferometry setup for testing the DSM as well as a full atmospheric turbulence simulator and star simulator to mimic the conditions at the telescope. To test the instruments using the DSM, the output beam is matched the output beam of the VLT telescope, including the correct exit-pupil and high-quality imaging and a similar hardware interface is provided. Since one of the modes to be verified is nearly diffraction limited, also the thermal and vibrational stability are very important, with strong constraints on both the mechanical as well as the optical design

VLTI/VINCI observations of the nucleus of NGC 1068 using the adaptive optics system MACAO

International audienceWe present the first near-infrared K-band long-baseline interferometric measurement of the nucleus of the prototype Seyfert 2 Galaxy NGC 1068 with resolution lambda/B ˜ 10 mas obtained with the Very Large Telescope Interferometer (VLTI) and the two 8.2 m diameter Unit Telescopes UT 2 and UT 3. The adaptive optics system MACAO (Multi Application Curvature Adaptive Optics) was employed to deliver wavefront-corrected beams to the K-band commissioning instrument VINCI. A squared visibility amplitude of 16.3 ± 4.3% was measured for NGC 1068 at a sky-projected baseline length of 45.8 m and azimuth angle 44.9 deg. This value corresponds to a FWHM of the K-band intensity distribution of 5.0 ± 0.5 mas (0.4 ± 0.04 pc at the distance of NGC 1068) if it consists of a single Gaussian component. Taking into account K-band speckle interferometry observations (Wittkowski et al. \cite{wittkowski}; Weinberger et al. \cite{weinberger}; Weigelt et al. \cite{weigelt}), we favor a multi-component model for the intensity distribution where a part of the flux originates from scales clearly smaller than ˜5 mas (⪅0.4 pc), and another part of the flux from larger scales. The K-band emission from the small (⪅5 mas) scales might arise from substructure of the dusty nuclear torus, or directly from the central accretion flow viewed through only moderate extinction

ASSIST ::the test setup for the VLT AO facility

ASSIST: The Adaptive Secondary Setup and Instrument STimulator is the test setup for the verification and calibration of three elements of the VLT Adaptive Optics Facility.; the Deformable Secondary Mirror (DSM) the AO system for MUSE and HAWK-I (GALACSI and GRAAL). In the DSM testing mode the DSM will be tested using both interferometry and fast wave front sensing. In full AO mode, ASSIST will allow testing of the AO systems under realistic atmospheric conditions and optically equivalent to the conditions on the telescope. ASSIST is nearing its final design review and in this paper we present the current optical and mechanical design of ASSIST. In this paper we highlight some of the specific aspects of ASSIST that we are developing for ASSIST

VLTI/VINCI observations of the nucleus of NGC 1068 using the adaptive optics system MACAO

International audienceWe present the first near-infrared K-band long-baseline interferometric measurement of the nucleus of the prototype Seyfert 2 Galaxy NGC 1068 with resolution lambda/B ˜ 10 mas obtained with the Very Large Telescope Interferometer (VLTI) and the two 8.2 m diameter Unit Telescopes UT 2 and UT 3. The adaptive optics system MACAO (Multi Application Curvature Adaptive Optics) was employed to deliver wavefront-corrected beams to the K-band commissioning instrument VINCI. A squared visibility amplitude of 16.3 ± 4.3% was measured for NGC 1068 at a sky-projected baseline length of 45.8 m and azimuth angle 44.9 deg. This value corresponds to a FWHM of the K-band intensity distribution of 5.0 ± 0.5 mas (0.4 ± 0.04 pc at the distance of NGC 1068) if it consists of a single Gaussian component. Taking into account K-band speckle interferometry observations (Wittkowski et al. \cite{wittkowski}; Weinberger et al. \cite{weinberger}; Weigelt et al. \cite{weigelt}), we favor a multi-component model for the intensity distribution where a part of the flux originates from scales clearly smaller than ˜5 mas (⪅0.4 pc), and another part of the flux from larger scales. The K-band emission from the small (⪅5 mas) scales might arise from substructure of the dusty nuclear torus, or directly from the central accretion flow viewed through only moderate extinction

Silver (I) coordination chemistry: from 1-D chains to molecular rectangles

A series of silver(I) coordination compounds with the ligand 2-(4-pyridyl)imidazole 4-PyIm has been synthesized and crystallographically characterized in order to explore the role of counter ion, solvent and ligand charge on the resulting supramolecular architectures. With perchlorate and hexaflourophosphate, two iso-structural 1-D coordination-polymers were obtained, but when changing the counter ion to nitrate and using water as solvent, an unusual molecular rectangle composed of four ligands and four Ag(I) ions was obtained, and the assembly was controlled by hydrogen bonding via the anion and water molecules. Finally, when the ligand was deprotonated, the change in the number of binding sites (from two to three) was reflected in an increase in coordination number for the silver ion