Canton de Chemin (Jura)

Les communes de Neublans, Petit-Noir, Longwy-sur-le-Doubs et Annoire (Jura) ont fait l’objet de prospections qui ont révélé quelques découvertes de vestiges antiques (tuiles, briques, céramique) érodés pour la plupart par la présence du Doubs, ainsi que quelques indices médiévaux. Nous avons par ailleurs localisé une motte féodale (motte de Charmoncel), grâce à un texte de Feuvrier et au plan cadastral napoléonien de la commune de Petit-Noir (1825). En fin d’année 1999, avec la collaboration ..

Canton de Bouclans

La prospection s’est poursuivie en 1998 sur le canton de Bouclans, et plus particulièrement sur les communes de Bouclans et Champlive. La prospection sur la première commune citée ne s’est pas révélée fructueuse, avec seulement un fragment de meule en roche métamorphique et un grattoir sur éclat en silex. Les ruines du château de Vaîte, sur la commune de Champlive, ont été visitées, occasionnant la découverte d’un fragment de dalle médiévale

Canton de Bouclans

Seul le territoire communal de Bouclans a été prospecté en 1997. Au lieu-dit « Courbe Montée », ont été ramassés une quinzaine de silex, dont un biface de type acheuléen (Paléolithique moyen) et un grattoir (peut-être du Néolithique), quatre fragments de meule en grès rouge vosgien (Permien) dont certains sont noircis (peut-être brûlés) ainsi que six tessons de céramique grossière noire (protohistorique ou gallo-romaine). Chez une villageoise, au cours de travaux de jardinage, a été découvert..

Magnetic collimation of meridional-self-similar general relativistic MHD flows

We present a model for the spine of relativistic MHD outflows in the Kerr geometry. Meridional self-similarity is invoked to derive semi-analytical solutions close to the polar axis. The study of the energy conservation along a particular field line gives a simple criterion for the collimation of jets. Such parameter have already been derived in the classical case by Sauty et al. 1999 and also extended to the Schwarzschild metric by Meliani et al. 2006. We generalize the same study to the Kerr metric. We show that the rotation of the black hole increases the magnetic self-confinement.Comment: 16 pages, 6 figures, accepted for publication in Physical Review

Two-flow magnetohydrodynamical jets around young stellar objects

We present the first-ever simulations of non-ideal magnetohydrodynamical (MHD) stellar winds coupled with disc-driven jets where the resistive and viscous accretion disc is self-consistently described. The transmagnetosonic, collimated MHD outflows are investigated numerically using the VAC code. Our simulations show that the inner outflow is accelerated from the central object hot corona thanks to both the thermal pressure and the Lorentz force. In our framework, the thermal acceleration is sustained by the heating produced by the dissipated magnetic energy due to the turbulence. Conversely, the outflow launched from the resistive accretion disc is mainly accelerated by the magneto-centrifugal force. We also show that when a dense inner stellar wind occurs, the resulting disc-driven jet have a different structure, namely a magnetic structure where poloidal magnetic field lines are more inclined because of the pressure caused by the stellar wind. This modification leads to both an enhanced mass ejection rate in the disc-driven jet and a larger radial extension which is in better agreement with the observations besides being more consistent.Comment: Accepted for publication in Astrophysics & Space Science. Referred proceeding of the fifth Mont Stromlo Symposium Dec. 1-8 2006, Canberra, Australia. 5 pages, 3 figures. For high resolution version of the paper, please click here http://www.apc.univ-paris7.fr/~fcasse/publications.htm

Stellar Wind Models

International audienceI present here some ideas on how jets from low mass stars may evolve as the star evolves from class 0 to the main sequence through classes I, II, III. Analytical models and simulations suggest that the ejection start very early in the life of a low mass star from the edge of the disk. Then, the jet is progressively ejected from a more central part of the system composed by the star and its accretion disk. Once the disk itself evaporates, the jet becomes a mere wind from the star which has reached the main sequence. This wind should be similar to the well known solar wind. To illustrate this point, we show specific applications of meridionally self-similar models to jets from T Tauris with a low mass accretion rate, as well as for the solar wind. We also present numerical simulations of turbulent stellar jets surrounded by a magnetized disk wind, which clearly show that the stellar jet may be an essential ingredient in preventing too fast and too tight collimation of the disk jet. At this point, note that I shall call in the rest of the present review ``stellar jet'', the component of the wind originating from the star and its vicinity, by opposition to the ``disk wind'' or ``disk jet'' that corresponds to the component emerging from the disk and more specifically from the Keplerian disk. The analytical solution can be further extended to the relativistic domain. The same dichotomy seems to exist for extragalactic jets. While sub relativitic winds from Seyferts may correspond to radial winds, radio loud jets are comparable to YSO jets. Nevertheless the distinction between FRI and FRII jets may be more a problem of environment and efficiency of the magnetic rotator as FRI jets evolve in a rich external medium, while the opposite holds for FRII

Mémoire de synthèse : De la théorie aux modèles d'éjections

Jury : J. Lebourlot, I. Grenier, J. Heyvaerts, M. Rieutord, T. Lago, H. Sol, K. Tsinganos, E. TrussoniEjections from stars is a common phenomenon. Stellar or extra-galactic jets are characterized by strongly accelerated plasma in the form of a bipolar flow more or less collimated along the rotation axis of the source. We have analysed the role of rotation, pressure and magnetic fields in the processes of accelerating and collimating the plasma jets and on their stability. We have shown the existence in these flows of MHD horizons and ergospheres analogous to their well known counterparts in the metrics of Black Holes. Self similar models of jets and winds allowed us to define general physical criteria for the classification of outflows depending on their energy distribution. We have applied such models to various objects such as the solar wind, jets from Young Stellar Objets and jets from Active Galactic Nuclei. For these objects, specific extension to the relativistic domain is demanded which is a point under consideration.Les processus d'éjection de masse des étoiles sont un phénomène largement répandu. Les vents, les jets stellaires ou les jets extra-galactiques sont caractérisés par une forte accélération du plasma éjecté et une morphologie plus ou moins bipolaire, plus ou moins focalisée le long de l'axe de rotation de la source. Nous avons effectué différentes analyses des rôles de la pression, du champ magnétique et de la rotation du plasma dans les processus de formation et d'accélération des jets et sur leur stabilité. Les travaux exposés montrent, en particulier, le rôle essentiel du couplage magnétocentrifuge et du gradient de densité aussi bien dans la formation que dans la stabilisation des jets. L'étude des écoulements de vents de disques et de couronnes, nous a amené à étudier en détails le rôle des surfaces critiques et leur lien essentiel avec les conditions limites. Nous avons montré l'analogie des écoulements MHD avec la métrique des trous noirs : les surfaces critiques sont l'analogue des horizons. Il existe aussi des ergosphères MHD, distinctes des horizons, qui n'ont pas nécessairement le rôle prédominant qu'on leur a parfois accordé. Les modèles autosimilaires de vents de couronne nous ont permis d'établir des critères originaux sur la collimation des vents en jets et de relier la focalisation la distribution d'énergie sur la source. Par ailleurs, nous avons introduit la notion de rotateurs magnétiques efficaces et inefficaces pour distinguer entre les sources de jets confinés thermiquement et celles de jets confinés magnétiquement. L'application de ces modèles au vent solaire (données de la sonde Ulysse) et aux jets d'étoiles jeunes (jets de classes 2), nous a permis de valider les critères de collimation. Nous avons proposé un scénario pour l'évolution des jets en vents au cours de l'évolution stellaire, tout en proposant une autre origine pour la formation des jets protostellaires de classe 0. Par ailleurs, ces mêmes critères nous ont permis d'avancer une nouvelle interprétation de la classification des jets extragalactiques. Pour ces jets, une extension relativiste des modèles, sur laquelle nous travaillons, est cependant nécessaire

Stellar Wind Models

International audienceI present here some ideas on how jets from low mass stars may evolve as the star evolves from class 0 to the main sequence through classes I, II, III. Analytical models and simulations suggest that the ejection start very early in the life of a low mass star from the edge of the disk. Then, the jet is progressively ejected from a more central part of the system composed by the star and its accretion disk. Once the disk itself evaporates, the jet becomes a mere wind from the star which has reached the main sequence. This wind should be similar to the well known solar wind. To illustrate this point, we show specific applications of meridionally self-similar models to jets from T Tauris with a low mass accretion rate, as well as for the solar wind. We also present numerical simulations of turbulent stellar jets surrounded by a magnetized disk wind, which clearly show that the stellar jet may be an essential ingredient in preventing too fast and too tight collimation of the disk jet. At this point, note that I shall call in the rest of the present review ``stellar jet'', the component of the wind originating from the star and its vicinity, by opposition to the ``disk wind'' or ``disk jet'' that corresponds to the component emerging from the disk and more specifically from the Keplerian disk. The analytical solution can be further extended to the relativistic domain. The same dichotomy seems to exist for extragalactic jets. While sub relativitic winds from Seyferts may correspond to radial winds, radio loud jets are comparable to YSO jets. Nevertheless the distinction between FRI and FRII jets may be more a problem of environment and efficiency of the magnetic rotator as FRI jets evolve in a rich external medium, while the opposite holds for FRII

Jet simulations, experiments, and theory: ten years after JETSET, what is next ?

In 2008, the European FP6 JETSET project ended. JETSET, for Jet, Simulations, Experiments, and Theory, was a joint research network of European expert teams on protostellar jets. The present proceedings are a collection of contributions presenting new results obtained by those groups since the end of the JETSET program. This is also the occasion to celebrate Kanaris Tsinganos’ important contributions to this network and for his enlightening insight in the subject that inspired us all. Some of the former JETSET students are now in the academic world and the subject has never been so alive. So we present here a collection of results of what has been done in the field of protostellar jets in the past ten years from the theoretical, numerical, observational and experimental point of view. We also present new challenges in the field of protostellar jets and what we should expect from the development of new instruments and new numerical codes in the near future. We also gather results on the impact of the study of protostellar jets on other jet studies in particular on relativistic jets. As a matter of fact, it is time for a new network

Modélisation de vents et de jets relativistes

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF