Properties of the CO and H2_2O MOLsphere of the red supergiant Betelgeuse from VLTI/AMBER observations

Context. Betelgeuse is the closest red supergiant (RSG); therefore, it is well suited for studying the complex processes in its atmosphere that lead to the chemical enrichment of the interstellar medium. Aims. We intend to investigate the shape and composition of the close molecular layer (also known as the MOLsphere) that surrounds the star. This analysis is part of a wider program that aims at understanding the dynamics of the circumstellar envelope of Betelgeuse. Methods. On January and February 2011, Betelgeuse was observed using the Astronomical Multi-BEam combineR (AMBER) instrument of the Very Large Telescope Interferometer (VLTI) in the H and K bands. Using the medium spectral resolution of the instrument (R $\sim$ 1500), we were able to investigate the carbon monoxide band heads and the water-vapor bands. We used two different approaches to analyse our data: a model fit in both the continuum and absorption lines and then a fit with a Radiative HydroDynamics (RHD) simulation. Results. Using the continuum data, we derive a uniform disk diameter of $41.01 \pm 0.41$~mas, a power law type limb-darkened disk diameter of $42.28 \pm 0.43$~mas and a limb-darkening exponent of $0.155 \pm 0.009$. Within the absorption lines, using a single layer model, we obtain parameters of the MOLsphere. Using a RHD simulation, we unveil the convection pattern in the visibilities. Conclusions. We derived a new value of the angular diameter of Betelgeuse in the K band continuum. Our observations in the absorption lines are well reproduced by a molecular layer at 1.2 stellar radii containing both CO and H$_2$O. The visibilities at higher spatial frequencies are matching a convection pattern in a RHD simulation.Comment: 13 pages, 11 figures, accepted for publication in Astronomy & Astrophysics; Language editin

Les collections du Midi, une méridionalité en trompe l’œil

Ce dossier intitulé « Collections méridionales. XVIe s. – XVIIIe s. » pour LIAME est en partie issu d’une journée d’études sur le même thème organisée au sein du laboratoire CRISES à l’Université Paul Valéry le 15 décembre 2014. Trois des articles du dossier en sont issus et un autre s’y est ajouté. Le numéro est aussi l’occasion de publier les inventaires manuscrits de deux cabinets languedociens, celui de Séguier à Nîmes et celui de la collection d’histoire naturelle de la municipalité de M..

Les amours de Mars et Flore aux cabinets. Les confiscations naturalistes en Europe Septentrionale 1794-1795

En 1794 et 1795, suivant le parcours des armées révolutionnaires, des commissions sont envoyées en Europe septentrionale pour y confisquer œuvres d’art, livres et spécimens d’histoire naturelle. Les confiscations d’histoire naturelle vont être justifiées par trois discours : le discours martial, le discours physiocratique et le discours républicain. La pratique des saisies naturalistes vise alors les clercs et les émigrés comme en France à partir de 1792. Les spécimens confisqués sont destinés tantôt au Muséum d’histoire naturelle tantôt aux futures collections départementales selon leur rareté : les pièces rares sont envoyées au Muséum pour compléter les collections de l’institution centrale dans une perspective encyclopédiste ; les plus communes sont destinées aux futurs musées départementaux liés aux écoles centrales dans une perspective ouvertement pédagogique.In 1794 and 1795, following the paths of the revolutionary armies, “commissaries” were sent into Southern Europe to confiscate works of art, books and specimens of natural history. The confiscations of natural history were justified by three rationale: the martial, the physiocratic, and the republican. The practice of seizures was chiefly aimed at ecclessiastics and emigres, as in France beginning in 1792. The specimens confiscated were destined sometimes for the Museum of Natural History sometimes for the departmental collections, depending on their rarity: the rare objects were sent to the Museum to complete the collections of the central institution in an encyclopedist perspective; the more common objects were sent to the future departmental museums linked to the “écoles centrales” with a openly pedagogical intent

Inventaire du cabinet d’histoire naturelle de Montpellier en 1806

Note de l’éditeur : L’inventaire de sept pages du cabinet d’histoire naturelle de Montpellier a été rédigé en octobre 1806 par André-Antoine Touchy (1752-1814). Issu d’une famille montpelliéraine de négociants, officiers et chirurgiens, il est lui-même magistrat à Montpellier sous l’Ancien Régime puis professeur d’histoire à l’École centrale de l’Hérault sous la Révolution et, enfin, professeur du lycée et conservateur de la collection d’histoire naturelle de la ville sous l’Empire. Dans ces ..

Coquilles et médailles. Naturalia et artificialia dans les collections de province autour de la Révolution

Dans le moment révolutionnaire, tout particulièrement lors des grandes (re)fondations des années 1793-1795, les collections parisiennes tendent à se spécialiser rapidement dans l’un ou l’autre des quatre grands domaines d’objets matériels : la nature, les antiquités, les techniques et les beaux-arts. Autour de 1800, les collections qui rejettent ce modèle de spécialisation et associent naturalia et artificialia sont démonétisées, à l’image des cabinets provinciaux, qu’ils soient particuliers ou institutionnels. Si, vers 1810, les collections provinciales mêlent encore des objets naturels et artificiels, ces derniers ne sont plus les mêmes que dans les années 1780, les artefacts exotiques étant tantôt rendus invisibles tantôt ordonnés dans une histoire de l’industrie humaine. Le couplage coquilles (ou minéraux) et médailles (ou antiquités) est alors la règle. Il conviendrait de ne pas lire dans ces mélanges d’objets hétéroclites l’incarnation d’un projet intellectuel de mise en rapport des savoirs mais d’y voir, plus prosaïquement, des rassemblements contingents liés à l’histoire même des collections.Around the time of the French Revolution, and more particularly during the major (re)organisations of 1793–1795, Parisian collections were rapidly beginning to specialise in one of the four main areas of physical objects, namely nature, antiquities, technology and fine arts. By around 1800, collections that were rejecting this specialisation model and combining naturalia and artificialia had come to be devalued in the same way that private and institutional provincial collections were. Although the provincial collections were still combining natural and artificial objects by around 1810, the latter were different from those exhibited in the 1780s. The exotic artefacts had either become invisible, or they had been organised into a history of human industry. The pairing of shells (or minerals) and medals (or antiquities) had therefore become the norm. This mixing of heterogenous objects should not be interpreted as the manifestation of an intellectual project that formed connections between different areas of knowledge but rather, somewhat more prosaically, as contingent assemblages that were linked to the very history of collections itself

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

As the nearest known AGB star (d=64pc) and one of the brightest (mK-2), L2 Pup is a particularly interesting benchmark object to monitor the final stages of stellar evolution. We report new lucky imaging observations of this star with the VLT/NACO adaptive optics system in twelve narrow band filters covering the 1.0-4.0 microns wavelength range. These diffraction limited images reveal an extended circumstellar dust lane in front of the star, that exhibits a high opacity in the J band and becomes translucent in the H and K bands. In the L band, extended thermal emission from the dust is detected. We reproduce these observations using Monte-Carlo radiative transfer modeling of a dust disk with the RADMC-3D code. We also present new interferometric observations with the VLTI/VINCI and MIDI instruments. We measure in the K band an upper limit to the limb-darkened angular diameter of theta_LD = 17.9 +/- 1.6 mas, converting to a maximum linear radius of R = 123 +/- 14 Rsun. Considering the geometry of the extended K band emission in the NACO images, this upper limit is probably close to the actual angular diameter of the star. The position of L2 Pup in the Herzsprung-Russell diagram indicates that this star has a mass around 2 Msun and is probably experiencing an early stage of the asymptotic giant branch. We do not detect any stellar companion of L2 Pup in our adaptive optics and interferometric observations, and we attribute its apparent astrometric wobble in the Hipparcos data to variable lighting effects on its circumstellar material. We however do not exclude the presence of a binary companion, as the large loop structure extending to more than 10 AU to the North-East of the disk in our L band images may be the result of interaction between the stellar wind of L2 Pup and a hidden secondary object. The geometric configuration that we propose, with a large dust disk seen almost edge-on, appears particularly favorable to test and develop our understanding of the formation of bipolar nebulae.Comment: 16 pages, 15 figure

Analyses des consommations énergétiques des tracteurs en usage réel : application aux chantiers d'épandage

National audienceAfin de réduire la facture énergétique de l'agriculture, il faut pouvoir améliorer l'efficacité des machines utilisées, mais aussi celle des méthodes de productions agricoles. À partir d'une campagne d'expérimentations sur le travail d'épandage, les auteurs nous montrent ici comment produire des indicateurs pertinents pour évaluer la performance énergétique d'une opération agricole

Mechanical determinants of 100-m sprint running performance

International audienceSprint mechanics and field 100-m performances were tested in 13 subjects including 9 non-specialists, 3 French national-level sprinters and a world-class sprinter, to further study the mechanical factors associated with sprint performance. 6-s sprints performed on an instrumented treadmill allowed continuous recording of step kinematics, ground reaction forces (GRF), and belt velocity and computation of mechanical power output and linear force–velocity relationships. An index of the force application technique was computed as the slope of the linear relationship between the decrease in the ratio of horizontal-to-resultant GRF and the increase in velocity. Mechanical power output was positively correlated to mean 100-m speed (P0.683; P0.21). Last, anthropometric data of body mass index and lowerlimb- to-height ratio showed no significant correlation with 100-m performance. We concluded that the main mechanical determinants of 100-m performance were (1) a ‘‘velocity-oriented’’ force–velocity profile, likely explained by (2) a higher ability to apply the resultant GRF vector with a forward orientation over the acceleration, and (3) a higher step frequency resulting from a shorter contact time