Archives Séminaires 2015-2016

Séminaire

Séminaire IPAG de Roxanne Ligi (LAM), jeudi 7 janvier 2016 à 11h00, IPAG seminar room

Accurate stellar parameters are needed in numerous domains of astrophysics. In particular, stellar parameters are required elements for studying exoplanetary systems, including their story. I will present the results of an interferometric survey of 18 bright exoplanet host and potential host stars using the VEGA/CHARA interferometer operating in the visible domain. We measured their angular diameters and combined them with their distance to get their radius. We used photometry to derive (…)

Séminaire

Séminaire IPAG de Antoine Gusdorf (LERMA), jeudi 14 janvier 2016 à 11h00, IPAG seminar room

In this talk, I will review the recent advances made on the understanding of interstellar shocks. The interstellar medium is an out-of-equilibrium medium, where energy is constantly injected in various forms : mechanical energy, photons, or cosmic rays. The propagation of shock waves is ubiquitous in the interstellar medium, where it represents an important part of the mechanical energy input. Interstellar shocks are generated by the birth (jets and bipolar outflows) or death (supernova and (…)

Séminaire

Isotopes are an invaluable tool to study the history of planetary systems. As an example, the D/H ratios observed in the various bodies of the solar system give insights on the Earth formation scenarios. While the effects responsible of the enrichment/depletion of molecules in a particular isotope are usually identified, it is however often difficult to obtain quantitative contraints and to disentengle the relative contributions of the various processes at work. In particular, the respective (…)

Séminaire

Séminaire IPAG de Alexis Matter (Lagrange), jeudi 28 janvier 2016 à 11h00, IPAG seminar room

MATISSE is the second generation mid-infrared spectrograph and imager for the Very Large Telescope Interferometer (VLTI) at Paranal. This new interferometric instrument will allow significant advances by opening new avenues in various fundamental research fields : studying the planet-forming region of disks around young stellar objects, understanding the surface structures and mass loss phenomena affecting evolved stars, and probing the environments of black holes in active galactic nuclei. (…)

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Séminaire IPAG de Vianney Taquet (University of Leiden), jeudi 4 février 2016 à 11h00, IPAG seminar room

The early phases of star formation are accompanied by a process of chemical complexity. Several Complex Organic Molecules (COMs), molecules based on carbon chemistry and with more than 5 atoms, have been detected in large quantities around high-mass and low-mass protostars for several decades. The current scenario for the formation of these COMs, potentially at the origin of the prebiotic chemistry seen in our Solar System, is based on UV-induced warm grain surface chemistry occurring in the (…)

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Séminaire IPAG de Colin Folsom (IPAG), jeudi 11 février 2016 à 11h00, IPAG seminar room

The surface rotation rates of young solar-type stars vary rapidly with age from the end of the pre-main sequence through the early main sequence. Important changes in the dynamos operating in these stars may result from this evolution, which should be observable in their surface magnetic fields. Here we present a study aimed at observing the evolution of these magnetic fields through this critical time period. We observed stars in open clusters and stellar associations of known ages, and (…)

Séminaire exceptionnel

Séminaire IPAG de Gilles Henri (IPAG), lundi 15 février 2016 à 11h00, IPAG seminar room

Gravitationnal waves have been directly detected for the first time. The two major impacts of this discovery are that 1) the last prediction of Einstein’s General Relativity theory is observed 2) a new messenger is now available to probe the Cosmos. We will review the basics of gravitationnal waves, the observations of the LIGO/VIRGO experiments and explore the consequences of these new findings.

Séminaire

Séminaire IPAG de Caroline Terquem (University of Oxford), jeudi 3 mars 2016 à 11h00, IPAG seminar room

As of today, about 2000 objects have received the label of "confirmed" extrasolar planets. Recent observations indicate that a significant number of the Jupiter-type planets with very short periods are on an orbit which is inclined with respect to the equatorial plane of their host star. This is difficult to explain in the context of planets forming in a protostellar disc assumed to lie in that plane.
In this talk, I will review different mechanisms that have been proposed to account for (…)

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Séminaire IPAG de Hervé Beust (IPAG), jeudi 10 mars 2016 à 11h00, IPAG seminar room

Il y a quelques semaines, Batygin & Brown (2016) ont annoncé que selon leurs travaux, la présence d’une planète supplémentaire dans la partie externe du système solaire était rendue nécessaire par la structuration spatiale des orbites des petits corps les plus externes découverts ces dernières années. La presse a immédiatement parlé de "découverte" de planète, ce qui est bien entendu exagéré. Je reviens sur ce sujet, en abordant tout d’abord l’aspect historique de la question. Je (…)

Séminaire

Séminaire IPAG de Mary Oksala (LESIA), jeudi 17 mars 2016 à 11h00, IPAG seminar room

Currently, the main tool for studying the magnetic fields and magnetospheres of hot, early-type stars is optical spectra. The signatures of magnetospheres appear as emission features in the Balmer series, typically only strongly visible in the Halpha line. Recently, we have begun to explore magnetospheres via infrared spectroscopy. Infrared spectroscopic evidence of magnetospheric material has several advantages over optical in that there are many more hydrogen lines to study, the detection (…)