The optical turbulence above Dome C in winter is mainly concentrated in the first tens of meters above the ground. The properties of this so-called surface layer were investigated during the last two ...winterover by a set of sonics anemometers placed on a 45 m high tower. These anemometers provide measurements of the temperature and the wind speed vector. The sampling rate of 10 Hz allows to derivate the refractive index structure constant Cn2. We report here the first analysis of these data.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
We present the latest results of our on-going closed-loop “end-to-end” numerical adaptive optics (AO) simulations concerning both a standard-AO and a three-star ground-layer AO system for a ...near-infrared 2-m class telescope at Dome C, Antarctica. We demonstrate that Dome C is an ideal site for wide-field AO-aided astronomy, define in details the AO system(s) optimized for the median turbulence profile considered, and finally show that a ~0.3 Strehl ratio and 200-mas-wide stable point-spread function is reached in band J on at least a 15'-diameter field.
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Multicolor differential photometry measurements of the two components of 18 close binary stars, mostly composite spectrum stars, are presented. They are based on observations made at Pic du Midi ...Observatory with the speckle camera PISCO between 1993 and 1998. Optical bench experiments were also performed to assess the validity of the whole process from the data acquisition with the ICCD detector to the final photometry measurements. The results are discussed and compared with (1) Hipparcos and speckle photometry, (2) spectroscopic measurements, and (3) composite spectra computed with a spectral library. Our measurements are in good agreement with other observations. We also determined the evolution stage of the individual components: the absolute visual magnitudes of the cool giant stars that we found are compatible with the calibrations made by other authors. This work shows that PISCO is well adapted to efficiently perform relative photometry of close binary stars.
We present relative astrometric measurements of visual binaries, made in 2014 with the speckle camera Pupil Interferometry Speckle camera and COronagraph (PISCO) at the 102‐cm Zeiss telescope of ...Brera Astronomical Observatory, in Merate. Our observing list contains orbital couples as well as binaries whose motion is still uncertain. We obtained 224 new measurements of 218 visual binary stars, with angular separations in the range 0′′.15–10′′, and an average accuracy of 0′′.015. The mean error on the position angles is 0°.5. Most of the position angles were determined without the usual 180° ambiguity with the application of triple‐correlation techniques and/or by inspection of the long integration files. We complete this data with the results of a study of the multiple system ADS 6993 with PISCO during the period 2004–2014 and propose a new method to resolve part of the 180‐degree ambiguity with the autocorrelations only. We then present new revised orbits for ADS 671, 1615, 1709, 5447, 10075, and 12447, partly derived from PISCO observations. The corresponding estimated values for the masses of those systems are compatible with the spectral types.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
From speckle observations made with the PISCO speckle camera at the Pic du Midi Observatory, we present high angular resolution astrometric data for 43 binary stars already observed by the Hipparcos ...satellite. This sample consists of mainly new Hipparcos eclipsing binaries with a visual companion closer than one arcsecond, chosen with the aim to study the dynamical implications of a third component on the observational parameters of the eclipsing system. In addition, we also included a selection of close visual binaries with few speckle data in order to analyse possible systematic departures between the speckle and the non-speckle orbits. The reduction method and the results are presented in detail. For the close visual binaries we confront our observations with the ephemerides based on the best known orbits. For the wide visual binaries the confrontation is made directly with the Hipparcos data. Our observations are consistent both with previous speckle data and with most of the Hipparcos measurements.
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Context. The winter seeing at Concordia is bimodal, i.e. either excellent or quite poor, depending on the altitude above the snow surface. We study the temporal behavior of the good seeing sequences. ...Efficient exploitation of extremely good seeing conditions with an adaptive optics system requires long integrations. Aims. We examine the temporal distribution of time intervals providing excellent seeing at Concordia. Methods. We create temporal windows of good seeing by applying a simple binary process: good or bad. We correct the autocorrelations of these windows for those of the existing data sets, since these are not continuous, often being interrupted by technical problems in addition to the adverse weather gaps. We infer the typical duration of good seeing sequences from these corrected autocorrelations. This study has to be a little detailed as its results depend on the season, summer or winter. Results. When we adopt a threshold of 0.5 arcsec to define “good seeing”, we find that three characteristic numbers describe the temporal evolution of the good seeing windows. The first number is the mean duration of an uninterrupted good seeing sequence, which is τ0 = 7.5 h at 8 m above the ground and 15 h at 20 m. These sequences are randomly distributed in time, following a negative exponential law of damping time τ1 = 29 h (at elevation 8 m and 20 m), which represents our second number. The third number is the mean time between two 29 h episodes, which is T = 10 days at 8 m high (5 days at 20 m). Conclusions. There is certainly no other site on Earth, except for the few other high altitude Domes on the Antarctic plateau, at which we can achieve these exceptionally high quality seeing conditions.
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So as to prepare future observations of terrestrial extrasolar planets liable to shelter life, we attempt to detect the life on the Earth seen as a dot. We use the Moon Earthshine, in which any place ...reflects the totality of the enlightened part of Earth facing the Moon. Observing from OHP and from ESO, we detected terrestrial chlorophyll in the near infrared, the so-called Vegetation Red Edge, and this detection is larger when forests are present than when an ocean is mainly visible from the Moon. Only if observations are made from a high latitude location, and at some moments in the year, Earthshine can be observed during a large part of the day. During these long observing windows, different “landscapes" are facing the Moon. So the Earthshine corresponding to various parts of our Earth could be studied. Preliminary testing observations have been made at Concordia since the first winterover campaign and the LUCAS experiment has been set up.
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