Archives Séminaires 2016-2017

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Séminaire IPAG de Gaitee Hussain (ESO), jeudi 8 septembre 2016 à 11h00, IRAM seminar room

Solar-type stars display signs of magnetic activity at all wavelengths, from energetic X-ray and UV flares to photometric variability caused by large cool spots. The rotation rate, internal structure and age of a main sequence star control critical aspects of its magnetic behaviour. For pre-main sequence stars however these trends are harder to find — these systems are particularly interesting as this is when the bulk of planet formation is likely to occur.
Over the past two decades (...)

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Séminaire IPAG de Jean Lilensten (IPAG), jeudi 15 septembre 2016 à 11h00, salle Manuel Forestini IPAG

For the last years, we have been discovering the polarisation of the auroral red line both in the cusp and in the auroral oval. We have proven that its Degree of Linear Polarisation (DoLP) varies accordingly to the geomagnetic activity. In the last 2 winters, two major steps have been achieved, that will be reported in this contribution. The first one is the calibrated determination of the Angle of Linear Polarisation (AoLP) during a winter at Ny Alesund (Svalbard). We have shown that it (...)

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Séminaire IPAG de Annie Hugues (IRAP), jeudi 22 septembre 2016 à 11h00, salle Manuel Forestini IPAG

Cloud-scale models of star formation predict that the transformation of gas into stars depends on the local density, turbulent velocity dispersion, and gravitational boundedness of the interstellar gas. With new facilities (ALMA/NOEMA), the latest generation of nearby galaxy surveys will systematically access these conditions in other galaxies at the scale of individual star-forming clouds. This is a major opportunity for linking the cloud-scale physics of star formation to galactic-scale (...)

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Séminaire IPAG de Antoine Petiteau (APC), jeudi 6 octobre 2016 à 11h00, salle Manuel Forestini IPAG

On the 7th June 2016, the first results of LISAPathfinder have been announced. LISAPathfinder is a technological demonstrator for a space-based gravitational waves observatory as LISA (Laser Interferometer Space Antenna) mission. It is a laboratory in space for testing the key LISA technologies as the free-fall of proof-masses and the high precision interferometry. The residual differential acceleration between the two proof masses of LISAPathfinder is less than 5*10^-15 m.s^-2.Hz^-1/2 more (...)

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Séminaire IPAG de Benoît Cerutti (IPAG), jeudi 13 octobre 2016 à 11h00, salle Manuel Forestini IPAG

Pulsars shine throughout the electromagnetic spectrum, from radio waves to energetic gamma rays, but the origin of the emitted radiation is still poorly understood. The recent development of global particle-in-cell (PIC) simulations allows, for the first time, to address this problem from first principles and self-consistently. Three-dimensional radiative PIC simulations show that the equatorial current sheet forming in the pulsar wind is the main site of particle acceleration, instead of (...)

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Séminaire IPAG de Florian Gallet (Université de Genève), jeudi 3 novembre 2016 à 11h00, salle Manuel Forestini IPAG

The number and quality of the stellar and planetary measurements has continuously increased during the last two decades. To account for the complex patterns and features that we start to distinguish in these observations, we now need to go one step forward in stellar and planetary numerical codes by including the interaction between a rotating star and its orbiting planet(s). Indeed, stellar surface rotation rate and planetary orbital radius are both directly affected by such interaction. (...)

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Séminaire IPAG de Sergio Blanco-Cuaresma (Université de Genève), jeudi 10 novembre 2016 à 11h00, salle Manuel Forestini IPAG

The chemical tagging technique proposed by Freeman & Bland-Hawthorn 2002 is based on the idea that stars formed from the same molecular cloud should share the same chemical signature. Thus, using only the chemical composition of stars we should be able to re-group the ones that once belonged to the same stellar aggregate. In Blanco-Cuaresma et al. 2015, we tested the technique using Open Cluster stars using iSpec (Blanco-Cuaresma et al. 2014), we demonstrated their chemical homogeneity (...)

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Séminaire IPAG de Gerrit van der Plas (University of Chile), jeudi 17 novembre 2016 à 11h00, salle Manuel Forestini IPAG

Disks around young stars are where all the planet-forming action happens. However, the specifics of disk dissipation and planet formation are still a hot topic of debate. Recent observations with the Atacama Large Millimeter/submillimeter Array (ALMA) highlight these issues with exquisite images of a few disks (and counting).
One of the long standing issues, for example, is why disks around the more massive Herbig Ae/Be stars seem to split into two families (group I and group II) when (...)

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Séminaire IPAG de Antoine Riols (Cambridge University), jeudi 24 novembre 2016 à 11h00, salle Manuel Forestini IPAG

Wind and jets, from protostellar to AGN discs, have been observed for decades and extensively studied but their connection to the turbulent dynamics of the underlying accretion disc is still poorly understood. Recently, it has been shown that the magnetorotational instability (MRI), often associated to turbulent activity and accretion in discs, might be also a key process in producing and accelerating outflows from the disc midplane. We conducted a suite of one-dimensional shearing-box (...)

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Séminaire IPAG de Timea Csengeri (MPI Bonn), jeudi 1er décembre 2016 à 11h00, salle Manuel Forestini IPAG

The origin of the highest mass stars is still an enigma in modern astrophysics. Only massive clumps, at the onset of star formation, can reveal the initial conditions and shed light on the necessary physical processes leading to their formation. The 870 micron ATLASGAL survey of the inner Galaxy is ideally suited to search for massive clumps still at their early evolutionary stage. Based on ATLASGAL, we identified the complete sample of infrared quiet massive clumps located at a distance (...)