The first astronomical seeing monitoring has been made with a DIMM instrument at the Antarctic plateau site of Dome C in December, 2002 on the bright star Canopus (α Eri) during the daytime. In these ...far from optimal conditions, a median seeing value of 1.20 arcsec as been obtained, with extended periods better than 1 arcsec and 12 percent of the time better than 0.75 arcsec.
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We present relative astrometric measurements of visual binaries made during the first semester of 2005, with the Pupil Interferometry Speckle Camera and Coronagraph (PISCO) at the 102-cm Zeiss ...telescope of the Brera Astronomical Observatory, in Merate. We performed 214 new observations of 192 objects, with angular separations in the range 0.2–4.3 arcsec, and with an average accuracy of 0.01 arcsec. Most of the position angles could be determined without the usual 180° ambiguity, and their mean error is . Our sample contains orbital couples as well as binaries whose motion is still uncertain. The purpose of this long-term programme is to improve the accuracy of the orbits and constrain the masses of the components. For the first time with PISCO, the astrometric calibration was made with a grating mask mounted at the entrance of the telescope. The advantage of this procedure is to provide a reliable and fully independent scale determination. We have found two possible new triple systems: ADS 7871 and KUI 15. We propose a preliminary orbit for ADS 4208.
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We present relative astrometric measurements of visual binaries made during the first semester of 2006, with the Pupil Interferometry Speckle camera and COronagraph at the 102-cm Zeiss telescope of ...the Brera Astronomical Observatory, in Merate. Our sample contains orbital couples as well as binaries whose motion is still uncertain. We obtained 217 new measurements of 194 objects, with angular separations in the range 0.1–4.2 arcsec, and an average accuracy of 0.01 arcsec. The mean error on the position angles is 0°.5. About half of those angles could be determined without the usual 180° ambiguity by the application of triple-correlation techniques. We also present a revised orbit for ADS 277 for which the previously published orbit resulted in a large residual from our measurements.
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This paper describes a method of beam-combination in the so-called hypertelescope imaging technique recently introduced by Labeyrie in optical interferometry. The method we propose is an alternative ...to the Michelson pupil reconfiguration that suffers from the loss of the classical object-image convolution relation. From elementary theory of Fourier optics we demonstrate that this problem can be solved by reconfiguring images instead of pupils. Imaging is performed in a combined pupil-plane where the point-source intensity distribution (PSID by comparison to the more commonly quoted point-spread function, PSF) tends towards a pseudo Airy disc for a sufficiently large number of telescopes. Our method is applicable to snap-shot imaging of extended sources with a field limited to the Airy pattern of single telescopes operated in a co-phased multi-aperture interferometric array. It thus allows to apply conveniently pupil plane coronagraphy. Our technique called Interferometric Remapped Array Nulling (IRAN) is particularly suitable for high dynamic imaging of extra-solar planetary companions or extra-galactic objects where long baseline interferometry would closely probe the central regions of AGNs for instance. We also discuss the application of IRAN to improve the performances of imaging and/or nulling interferometers like the full-fledged VLTI array or the DARWIN space-borne mission.
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This paper presents some statistical information about the Concordia turbulent surface inversion layer, regarding height and turbulent energy, its contribution to the peculiar local seeing, and the ...free atmosphere seeing encountered just above this surface layer.
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We present relative astrometric measurements of visual binaries taken during the second semester of 2004 with the Pupil Interferometry Speckle camera and Coronagraph (PISCO) at the 1-m Zeiss ...telescope of the Brera Astronomical Observatory, in Merate, Italy. We performed 207 new observations of 194 objects with angular separations in the range 0.1–4.0 arcsec and an accuracy better than ∼0.01 arcsec. Our sample contains orbital couples as well as binaries whose motion is still uncertain. Our purpose is to improve the accuracy of the orbits and constrain the masses of the components. Those measurements show that the orbit of ADS 15115 needs to be revised; we propose a new orbit for this object.
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We present relative astrometric measurements of visual binaries made with the Pupil Interferometry Speckle camera and Coronagraph (PISCO) at the 1-m Zeiss telescope of Brera Astronomical Observatory, ...in Merate. We provide 135 new observations of 103 objects, with angular separations in the range 0.1–4.0 arcsec and with an accuracy better than ∼0.01 arcsec. Our sample is made of orbital couples as well as binaries whose motion is still uncertain. Our purpose is to improve the accuracy of the orbits and constrain the masses of the components. This work already leads to the revision of the orbits of three systems (ADS 5447, 8035 and 8739).
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M-type (22) Kalliope: A tiny Mercury Ferrais, M.; Jorda, L.; Vernazza, P. ...
Astronomy and astrophysics (Berlin),
06/2022, Volume:
662
Journal Article, Web Resource
Peer reviewed
Open access
Context.
Asteroid (22) Kalliope is the second largest M-type asteroid in the main belt and is orbited by a satellite, Linus. Whereas the mass of Kalliope is already well constrained thanks to the ...presence of a moon, its volume is still poorly known, leading to uncertainties on its bulk density and internal structure.
Aims.
We aim to refine the shape of (22) Kalliope and thus its diameter and bulk density, as well as the orbit of its moon to better constrain its mass, hence density and internal structure.
Methods.
We acquired disk-resolved observations of (22) Kalliope using the VLT/SPHERE/ZIMPOL instrument to reconstruct its three-dimensional (3D) shape using three different modeling techniques. These images were also used together with new speckle observations at the C2PU/PISCO instrument as well as archival images from other large ground-based telescopes to refine the orbit of Linus.
Results.
The volume of (22) Kalliope given by the shape models, corresponding to
D
= 150 ± 5 km, and the mass constrained by its satellite’s orbit yield a density of
ρ
= 4.40 ± 0.46 g cm
−3
. This high density potentially makes (22) Kalliope the densest known small body in the Solar System. A macroporosity in the 10–25% range (as expected for this mass and size), implies a grain density in the 4.8–5.9 g cm
−3
range. Kalliope’s high bulk density, along with its silicate-rich surface implied by its low radar albedo, implies a differentiated interior with metal contributing to most of the mass of the body.
Conclusions.
Kalliope’s high metal content (40–60%) along with its metal-poor mantle makes it the smallest known Mercury-like body. A large impact at the origin of the formation of the moon Linus is likely the cause of its high metal content and density.
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