Archives Séminaires 2015-2016

Séminaire

Séminaire IPAG de Jesus Maldonado (INAF, Palermo), jeudi 10 septembre 2015 à 11h00, IPAG seminar room

Twenty years after the first exoplanet discoveries our understanding of what stellar properties influence (on how) planet formation is far to be complete. Excluding the well-established correlation between stellar metallicity and the probability that the star hosts a gas-giant planet, any other claim of a chemical trend in planet-hosting stars has been so far disputed. In the last years, detailed chemical abundance studies have reported different trends between samples of planet and (...)

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Séminaire IPAG de Bernard Schmitt (IPAG), jeudi 17 septembre 2015 à 11h00, IPAG seminar room

La mission New Horizons (NASA) a survolé Pluton et son système de satellites le 14 juillet de cette année. La mission a été un succès complet. Même si l’ensemble des données receillies vont mettre jusqu’à fin 2016 pour nous arriver au rythme de seulement 2kB/s (!) la sélection d’images retransmises jusqu’à présent a déjà permis de montrer des objets, Pluton et Charon en particulier, bien plus actifs géologiquement que ce que l’on pensait. Dans cet exposé je décrirai les instruments à bord (comportant (...)

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Séminaire IPAG de Luca Fossati (Space Research Institute of the Austrian Academy of Sciences), jeudi 24 septembre 2015 à 11h00, IPAG seminar room

Ultraviolet HST observations of close-in transiting planets showed that planet atmospheric evaporation is an important phenomenon playing a role in planet evolution, formation, habitability, and population. I will show our results obtained from the analysis of Hubble Space Telescope (HST) observations of the hot-Jupiters WASP-12b and WASP-13b. I will then show how planet evaporation may be at the origin of the correlation between the chromospheric activity of stars hosting hot-Jupiters and (...)

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Séminaire IPAG de Benoît Mosser (LESIA), jeudi 1er octobre 2015 à 11h00, IPAG seminar room

The space missions CoRoT and Kepler provide us with unique asteroseismic results that drastically change our views on the stellar interior structure. Inferring relevant estimates of the stellar masses and radii for field stars is now common, as well as determining their evolutionary status or the core rotation rate. A focus on red giant seismology helps understanding how new observable carry information on the stellar interior structure, including a direct view into the stellar core . (...)

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Séminaire IPAG de Gabriele Ponti (MPE, Garching), jeudi 5 novembre 2015 à 11h00, IPAG seminar room

The Milky Way centre hosts a supermassive Black Hole (BH) with a mass of ∼4×106M⊙. Sgr A∗, its electromagnetic counterpart, currently appears as an extremely weak source with a luminosity L∼10^-9 LEdd, occasionally showing flares lasting up to few hours. I will present evidence for an increase of the flaring activity and I will discuss the association of this behaviour with the peri-center passage of the G2 dusty object. In addition, I will give an overview of the past activity of Sgr A*, (...)

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Séminaire IPAG de Cécile Favre (IPAG), jeudi 12 novembre 2015 à 11h00, IPAG seminar room

One of the most important questions in the astrophysics of the interstellar medium (ISM) is whether, how, when, and where complex organic molecules (i.e. molecules that contain 6 or more atoms), including prebiotic species, are formed. And in the Interstellar-Earth connection context, could this have a bearing on the origin of life on Earth ? Formation mechanisms of complex organic species, which include potentially prebiotic molecules, are still much debated and may include grain-mantle (...)

Séminaire exceptionnel

Séminaire IPAG de Sebastien Muller (Chalmers University of Technology, Sweden), vendredi 20 novembre 2015 à 11h00, IPAG seminar room

The molecular absorber at z=0.89 in the line of sight of the lensed blazar PKS1830-211 is a unique source to investigate the physico-chemical properties of the ISM in the disk of a distant galaxy, with now about 50 different molecules detected.
I will present the latest ALMA results on this source (mostly focussing on hydride species), and show how the molecules can be used as powerful cosmological probes (temperature of the cosmic microwave background, evolution of isotopic ratios, (...)

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Séminaire IPAG de Jean-Pierre Lasota (IAP, N. Copernicus Astronomical Center), jeudi 26 novembre 2015 à 11h00, IPAG seminar room

According to a widely spread prejudice accretion onto compact bodies cannot be super-Eddington either in luminosity or in accretion rate. I will go over the old but generally ignored theoretical argument (Begelman 1979) showing that there is no limit on the accretion rate onto a black hole and present various astrophysical situations in which accretion luminosity can be super-Eddington. These theoretical considerations will be followed by a discussion of observations which clearly show the (...)

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Séminaire IPAG de Laurent Gremillet (CEA DAM), jeudi 3 décembre 2015 à 11h00, IPAG seminar room

In a few words : Powerful lasers have been built in the world and especially in France in Bordeaux, in order to develop experiments of compression of targets constituted of a mixture of deuterium-tritium in the purpose of getting thermonuclear fusion and an energy gain. These experiments have also been motivated by projects of fundamental physics, in particular by astrophysical projects. High energy astrophysics is rich of topics of investigations particularly well adapted to these (...)

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Séminaire IPAG de Quantin Kral (IoA Cambridge), jeudi 17 décembre 2015 à 11h00, IPAG seminar room

A non negligible quantity of gas has been discovered in an increasing number of debris disc systems. ALMA high sensitivity and high resolution is changing our perception of the gaseous component of debris discs as CO is discovered in systems where it should be rapidly photodissociated. It implies that there is a replenishment mechanism and that the observed gas is secondary. Past missions such as Herschel probed the atomic part of the gas through O I and C II emission lines. Gas science in (...)