Overview of the SAPHIRA Detector for AO Applications

We discuss some of the unique details of the operation and behavior of Leonardo SAPHIRA detectors, particularly in relation to their usage for adaptive optics wavefront sensing. SAPHIRA detectors are 320$\times$256@24 $\mu$m pixel HgCdTe linear avalanche photodiode arrays and are sensitive to 0.8-2.5 $\mu m$ light. SAPHIRA arrays permit global or line-by-line resets, of the entire detector or just subarrays of it, and the order in which pixels are reset and read enable several readout schemes. We discuss three readout modes, the benefits, drawbacks, and noise sources of each, and the observational modes for which each is optimal. We describe the ability of the detector to read subarrays for increased frame rates, and finally clarify the differences between the avalanche gain (which is user-adjustable) and the charge gain (which is not).Comment: 13 pages, 4 figures, 2 tables, accepted to JATI

LASSO: Large Adaptive optics Survey for Substellar Objects using the new SAPHIRA detector on Robo-AO

We report on initial results from the largest infrared AO direct imaging survey searching for wide orbit (>100 AU) massive exoplanets and brown dwarfs as companions around young nearby stars using Robo-AO at the 2.1-m telescope on Kitt Peak, Arizona. The occurrence rates of these rare substellar companions are critical to furthering our understanding of the origin of planetary-mass companions on wide orbits. The observing efficiency of Robo-AO allows us to conduct a survey an order of magnitude larger than previously possible. We commissioned a low-noise high-speed SAPHIRA near-infrared camera to conduct this survey and report on its sensitivity, performance, and data reduction process.Comment: 10 pages, 7 figures, SPIE conference proceeding

Large adaptive optics survey for substellar objects around Young, Nearby, Low-mass Stars with Robo-AO

We present results from the Large Adaptive optics Survey for Substellar Objects, where the goal is to directly image new substellar companions (<70 MJup) at wide orbital separations (≳50 au) around young (≲300 Myr), nearby (<100 pc), low-mass (≈0.1–0.8 M☉) stars. We report on 427 young stars imaged in the visible (i′) and near-infrared (J or H) simultaneously with Robo-AO on the Kitt Peak 2.1 m telescope and later the Maunakea University of Hawaii 2.2 m telescope. To undertake the observations, we commissioned a new infrared camera for Robo-AO that uses a low-noise high-speed SAPHIRA avalanche photodiode detector. We detected 121 companion candidates around 111 stars, of which 62 companions are physically associated based on Gaia DR2 parallaxes and proper motions, another 45 require follow-up observations to confirm physical association, and 14 are background objects. The companion separations range from 2 to 1101 au and reach contrast ratios of 7.7 mag in the near-infrared compared to the primary. The majority of confirmed and pending candidates are stellar companions, with ∼5 being potentially substellar and requiring follow-up observations for confirmation. We also detected a 43 ± 9 MJup and an 81 ± 5 MJup companion that were previously reported. We found 34 of our targets have acceleration measurements detected using Hipparcos–Gaia proper motions. Of those, 58-+1412% of the 12 stars with imaged companion candidates have significant accelerations (c2 > 11.8), while only 23-+611% of the remaining 22 stars with no detected companion have significant accelerations. The significance of the acceleration decreases with increasing companion separation. These young accelerating low-mass stars with companions will eventually yield dynamical masses with future orbit monitoring

LASSO: Large Adaptive optics Survey for Substellar Objects using the new SAPHIRA detector on Robo-AO

We report on initial results from the largest infrared AO direct imaging survey searching for wide orbit (≳ 100 AU) massive exoplanets and brown dwarfs as companions around young nearby stars using Robo-AO at the 2.1-m telescope on Kitt Peak, Arizona. The occurrence rates of these rare substellar companions are critical to furthering our understanding of the origin of planetary-mass companions on wide orbits. The observing efficiency of Robo-AO allows us to conduct a survey an order of magnitude larger than previously possible. We commissioned a low-noise high-speed SAPHIRA near-infrared camera to conduct this survey and report on its sensitivity, performance, and data reduction process

High contrast imaging upgrades for the Keck adaptive optics imager

The Keck II adaptive optics (AO) system is being upgraded with a near-infrared Pyramid Wavefront Sensor (PWS) as part of the Keck Planet Imager and Characterizer (KPIC) upgrade. The overview of the KPIC project and the PWS development are presented elsewhere in this conference. This paper focuses on improvements made to the NIRC2 science instrument, referred to as the NIRC2 upgrade, aimed at enhancing its high contrast imaging capabilities. The NIRC2 upgrade incorporates new coronagraphic elements that reach their maximum performance when operated in combination with the new near-infrared PWS and polarimetric elements that would add polarimetric capability when fully implemented. The key elements to the NIRC2 upgrade are the installation of two next-generation Vector Vortex Coronographic (VVC) masks, one optimized for the L and M band, and the other one optimized for the K band. Also key to the upgrade is the incorporation of a new Lyot stop optimized to minimize diffraction and residual nutation of the Keck-II telescope pupil. These new elements provide improved coronographic performance when operated with the new PWS and the existing Shack Hartmann wavefront sensor (SH WFS). The upgrade implementation and preliminary on-sky results are discussed. © 2019 AO4ELT 2019 - Proceedings 6th Adaptive Optics for Extremely Large Telescopes. All rights reserved

Large Adaptive Optics Survey for Substellar Objects around Young, Nearby, Low-mass Stars with Robo-AO

We present results from the Large Adaptive optics Survey for Substellar Objects, where the goal is to directly image new substellar companions ( 11.8), while only 23₋₆⁺¹¹% of the remaining 22 stars with no detected companion have significant accelerations. The significance of the acceleration decreases with increasing companion separation. These young accelerating low-mass stars with companions will eventually yield dynamical masses with future orbit monitoring

GPAW: open Python package for electronic-structure calculations

We review the GPAW open-source Python package for electronic structure calculations. GPAW is based on the projector-augmented wave method and can solve the self-consistent density functional theory (DFT) equations using three different wave-function representations, namely real-space grids, plane waves, and numerical atomic orbitals. The three representations are complementary and mutually independent and can be connected by transformations via the real-space grid. This multi-basis feature renders GPAW highly versatile and unique among similar codes. By virtue of its modular structure, the GPAW code constitutes an ideal platform for implementation of new features and methodologies. Moreover, it is well integrated with the Atomic Simulation Environment (ASE) providing a flexible and dynamic user interface. In addition to ground-state DFT calculations, GPAW supports many-body GW band structures, optical excitations from the Bethe-Salpeter Equation (BSE), variational calculations of excited states in molecules and solids via direct optimization, and real-time propagation of the Kohn-Sham equations within time-dependent DFT. A range of more advanced methods to describe magnetic excitations and non-collinear magnetism in solids are also now available. In addition, GPAW can calculate non-linear optical tensors of solids, charged crystal point defects, and much more. Recently, support of GPU acceleration has been achieved with minor modifications of the GPAW code thanks to the CuPy library. We end the review with an outlook describing some future plans for GPAW

Der Indocyaningruen-Leberfunktionstest zur Beurteilung von Leberkrankheiten des Hundes

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