Archives Séminaires 2012-2013

Séminaire

Séminaire IPAG de Samia Drappeau (U. of Amsterdam), jeudi 22 novembre 2012 à 11h00, IPAG seminar room

X-ray binaries (XRBs) are binary systems in which a compact object (neutron star or black hole) accretes matter from a companion star. The accretion processes onto a compact object emit strongly in the X-ray band, making XRBs the brightest sources of X-rays in our galaxy. Also associated with XRBs is radio emission from both discrete ejecta as well as collimated, compact jets. The jets are relativistic outflows launched from the vicinity of the compact object and are believed to be powerful (…)

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Séminaire IPAG de Asunción Fuente (OAN, Madrid), jeudi 29 novembre 2012 à 11h00, IPAG seminar room

The common paradigm for the formation of low mass stars includes the spherical infall of a cloud core, the formation of a disk with a protostar at its centre, and a bipolar outflow emitted from the inner region of this disk/ protostar structure. Our understanding of the formation of high mass stars is not so mature, although it is clear that there are some significant differences between the low mass and high mass formation mechanisms, including the fact that massive stars are predominantly (…)

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Séminaire IPAG de Ana Sepulcre (IPAG), jeudi 6 décembre 2012 à 11h00, IPAG seminar room

Broadband spectral surveys of star-forming regions offer a rich view of their physical, chemical and dynamical structure and evolution. Thanks to the Herschel guaranteed time key programme CHESS, we now have in our hands line-rich spectra of a selected sample of objects representing different aspects of the star formation process. These were observed with the HIFI spectrograph on-board the Herschel satellite, and cover most of the frequencies between 480 and 1900 GHz.
I will first present (…)

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Séminaire IPAG de Emeline Bomont (Obs. de Bordeaux), jeudi 13 décembre 2012 à 11h00, IPAG seminar room

I will show the results of the study the tidal evolution of close-in planets around 0.1 M-dwarfs and Sun-like stars. Contrary to BDs, the rotation of these objects is braked by stellar winds, so after decreasing slightly after the protoplanetary disk dispersal, the corotation radius increases with time. I found that assuming an initially slow rotating M-dwarf or Sun-like star affects only the very close-in planets. The planets initially inside corotation tend to fall on the central object. (…)

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Séminaire IPAG de Jérémie Boissier (ESO/INAF-Istituto di Radioastronomia), jeudi 20 décembre 2012 à 11h00, IPAG seminar room

As remnants of the planet formation era, comets are expected to hold iinformation about the physical and chemical conditions in the early Solar System. Millimeter spectroscopy enables the measurement of key parameters to characterize the cometary atmospheres, such as molecular abundances, gas temperature and outflow velocity. However limited information on the outgassing pattern can be retrieved from single dish observations, due to limited spatial resolution. Thanks to interferometric (…)

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Séminaire IPAG de Benoit Famaey (Obs. de Strasbourg), jeudi 10 janvier 2013 à 11h00, IPAG seminar room

We show that classical moving groups in the velocity field of the solar neighbourhood (e.g., the Hercules, Pleiades, Hyades and Sirius moving groups) are not made of co-eval stars. This favors a dynamical origin for these phase-space structures rather than the dissolution of open clusters. We show how such phase-space structures are indeed triggered by the non-axisymmetric features of the Galactic disk, namely the bar and spiral arms, and how radial migrations of stars through the Galactic (…)

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Séminaire IPAG de Amy Bonsor & Steve Ertel (IPAG), jeudi 17 janvier 2013 à 11h00, IPAG seminar room

Exozodiacal dust is hot dust at a distance of few AU down to the sublimation radius around main sequence stars. Although expected to be present in analogy to our own zodiacal dust, first observations of this phenomenon revealed surprising results and major differences to our own Solar System. Following time scale arguments, the dust cannot be produced at this position in a steady state collisional cascade of larger bodies as in a normal debris disk. On the other hand, transient events are (…)

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Séminaire IPAG de Chiara Feruglio (IRAM), jeudi 24 janvier 2013 à 11h00, IPAG seminar room

In the last few years, AGN-driven massive outflows have been seen in molecular gas component in several local QSOs/ULIRGs and mergers, and they start to be found in a few high redshift galaxies. These observational results show that outflows can invest the bulk of the gas in galaxies on scales as large as the kpc, supporting models of AGN and galaxy co-evolution through AGN-feedback. Molecular outflows are therefore regarded as the long sought mechanism leading to the formation of red (…)

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Séminaire IPAG de Nicolas Blind (MPE), jeudi 31 janvier 2013 à 11h00, IPAG seminar room

The next generation of Extremely Large Telescopes, with diameter up to 39 meters, is planned to begin operation on the horizon 2020 and promises new challenges in the development of instruments. Indeed, as the instrument size increases in proportion of the telescope diameter, the cost of future instruments could be as much as a single 10-m class telescope. The growing field of astrophotonics (the use of photonic technologies for astronomy) could partly solve this problem by allowing mass (…)

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Séminaire IPAG de Aurélien Crida (OCA), jeudi 7 février 2013 à 11h00, IPAG seminar room

In the rings of Saturn, self gravity is dominated by the tidal forces from the planet. Therefore, the boulders consituting the rings can not aggregate. However, the rings evolve viscously and spread (e.g. Salmon et al. 2010). As they spread beyond the Roche radius, the tides become weaker than the self gravity, and new satellites form. I will describe this process, and show that the regular satellites of Saturn most likely formed this way (Charnoz et al. 2010, 2011).
Then, I’ll present an (…)