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38 papers found.
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Fatigue of Drillstring: State of the Art

Failure due to fatigue is a very costly problem in oil and gas industry. Many investigators have previously addressed this problem, but its frequency of occurrence is still excessive. Torque and tension can be correctly predicted but computations of fatigue duration are still approximate. Regarding the fatigue failure of drillstring, this paper summarizes the state of the art...

General relativistic effects on the orbit of the S2 star with GRAVITY

Context. The first observations of the GRAVITY instrument obtained in 2016, have shown that it should become possible to probe the spacetime close to the supermassive black hole Sagittarius A* (Sgr A*) at the Galactic center by using accurate astrometric positions of the S2 star.Aims. The goal of this paper is to investigate the detection by GRAVITY of different relativistic...

Evolution of the magnetic field of Betelgeuse from 2009–2017

. Chiavassa 5 M. Montargès 4 R. Konstantinova-Antova 9 P. Kervella 8 G. Perrin 8 J.-F. Donati 1 J. Grunhut 2 0 Université de Montpellier , CNRS, LUPM, Place Eugène Bataillon, 34095 Montpellier , France 1 IRAP

Testing the validity of the ray-tracing code GYOTO

A&A Astronomy & Astrophysics M. Grould 0 T. Paumard 0 G. Perrin 0 0 LESIA, Observatoire de Paris, CNRS, Université Pierre Marie Curie, Université Paris Diderot , 5 place Jules Janssen, 92190

Asymmetries on red giant branch surfaces from CHARA/MIRC optical interferometry

. Perrin 9 G. H. Schaefer 8 T. A. ten Brummelaar 8 Z. Magic 2 11 R. Collet 12 M. Asplund 10 0 Institut de Radioastronomie Millimétrique , 300 rue de la Piscine, 38406 Saint-Martin d'Hères , France 1 CHARA

The close circumstellar environment of Betelgeuse - III. SPHERE/ZIMPOL imaging polarimetry in the visible

The physical mechanism through which the outgoing material of massive red supergiants is accelerated above the escape velocity is unclear. Thanks to the transparency of its circumstellar envelope, the nearby red supergiant Betelgeuse gives the opportunity to probe the innermost layers of the envelope of a typical red supergiant down to the photosphere, i.e. where the acceleration...

The dust disk and companion of the nearby AGB star L2 Puppis - SPHERE/ZIMPOL polarimetric imaging at visible wavelengths

, G. , & Perrin , G. 2002 , A &A, 393 , 183 Castelli , F. , & Kurucz , R. L. 2004 , ArXiv e-prints [arXiv:astro-ph/0405087] Cernicharo , J. , Marcelino , N. , Agúndez , M. , & Guélin , M. 2015 , A &A

Assessing stable isotope dynamics of diapausing Calanus finmarchicus and C. hyperboreus during the overwintering period: a laboratory experiment

laboratory experiment G. PERRIN C. DIBACCO S. PLOURDE G. WINKLER Corresponding Editor: Roger Harris This study aimed at describing changes in the stable isotopic composition of late copepodite stage V (CV

Discovery of a complex linearly polarized spectrum of Betelgeuse dominated by depolarization of the continuum

8 J.-F. Donati 0 3 J. H. Grunhut 2 G. A. Wade 12 F. Herpin 10 13 P. Kervella 5 11 G. Perrin 5 B. Tessore 7 0 CNRS, UMR 5277, Institut de Recherche en Astrophysique et Planétologie , 14 avenue

An edge-on translucent dust disk around the nearest AGB star, L2 Puppis - VLT/NACO spectro-imaging from 1.04 to 4.05 μm and VLTI interferometry

Bjorkman , J. E. , & Wood , K. 2001 , ApJ, 554 , 615 Bordé , P. , Coudé du Foresto, V. , Chagnon , G. , & Perrin , G. 2002 , A &A, 393 , 183 Bujarrabal , V. , Castro-Carrizo , A. , Alcolea , J. , & Neri , R

A Methodology to Construct Approximate Constitutive Equations for Porous Rubber Elastic Materials

The present paper makes use of methods from theory of ductile fracture, which was developed to prevent catastrophic failures of steel vessels, for example gas pipelines. A number of structures are made of porous materials, with elastic, isochoric matrix, or of such materials which may become porous when they are subjected to excessive mechanical loads. Predicting the behavior of...

Performance of astrometric detection of a hotspot orbiting on the innermost stable circular orbit of the Galactic Centre black hole

The Galactic Central black hole Sgr A* exhibits outbursts of radiation in the near-infrared (so-called IR flares). One model of these events consists in a hotspot orbiting on the innermost stable circular orbit (ISCO) of the hole. These outbursts can be used as a probe of the central gravitational potential. One main scientific goal of the second-generation VLTI instrument...

Dynamics of the ionization bicone of NGC 1068 probed in mid-infrared with VISIR

Context. We present high-spatial and medium-spectral resolution imaging and spectroscopy of the core of the Seyfert II galaxy NGC 1068, obtained in the N-band spectral range with the VLT/VISIR (the VLT Imager and Spectrometer in the InfraRed). Spectra were acquired in the ArIII 8.99 μm, SIV 10.51 μm and NeII 12.81 μm filters for two orientations of the long slit : PA = -15° and...

The close circumstellar environment of Betelgeuse - II. Diffraction-limited spectro-imaging from 7.76 to 19.50 μm with VLT/VISIR

Context. Mass-loss occurring in red supergiants (RSGs) is a major contributor to the enrichment of the interstellar medium in dust and molecules. The physical mechanism of this mass loss is however relatively poorly known. Betelgeuse is the nearest RSG, and as such a prime object for high angular resolution observations of its surface (by interferometry) and close circumstellar...

VLBA SiO observations of bright O-rich AGB stars

We present the results of observations of the SiO masers at 7 mm wavelength in several oxygen rich Asymptotic Giant Branch (AGB) stars. These observations were coordinated with observations using the ESO VLTI/MIDI interferometer at 10 μm wavelength. These stars are o Ceti (Mira), U Herculis (U Her), OH26.5+0.6, R Leonis (R Leo), and W Hydrae (W Hya). Both total intensity and...

High dynamic range imaging with a single-mode pupil remapping system: a self-calibration algorithm for redundant interferometric arrays

The correction of the influence of phase corrugation in the pupil plane is a fundamental issue in achieving high dynamic range imaging. In this paper, we investigate an instrumental set-up which consists of applying interferometric techniques on a single telescope, by filtering and dividing the pupil with an array of single-mode fibres. We developed a new algorithm, which makes...

The magnetic field of Betelgeuse: a local dynamo from giant convection cells?

Context. Betelgeuse is an M supergiant with a complex and extended atmosphere, which also harbors spots and giant granules at its surface. A possible magnetic field could contribute to the mass loss and to the heating of the outer atmosphere.Aims. We observed Betelgeuse, to directly study and infer the nature of its magnetic field.Methods. We used the new-generation...

Radiative hydrodynamics simulations of red supergiant stars - II. Simulations of convection on Betelgeuse match interferometric observations

Context. The red supergiant (RSG) Betelgeuse is an irregular variable star. Convection may play an important role in understanding this variability. Interferometric observations can be interpreted using sophisticated simulations of stellar convection.Aims. We compare the visibility curves and closure phases obtained from our 3D simulation of RSG convection with CO5BOLD to various...

High dynamic range imaging by pupil single-mode filtering and remapping

Because of atmospheric turbulence, obtaining high angular resolution images with a high dynamic range is difficult even in the near-infrared domain of wavelengths. We propose a novel technique to overcome this issue. The fundamental idea is to apply techniques developed for long baseline interferometry to the case of a single-aperture telescope. The pupil of the telescope is...

Revisiting the optical interferometry observations of HR 4049

Aims. We present high spatial resolution observations in the mid-infrared of the dusty core of the binary system HR 4049. Methods. We used the mid-infrared interferometer MIDI/VLTI with 40 m projected baselines. These observations provided two spectrally dispersed visibility curves at a spatial resolution of ~10 mas. Acquisition images and spectra are in addition obtained with a...