Archives Séminaires 2014-2015

Séminaire

Séminaire IPAG de Mitch Begelman (University of Colorado), jeudi 19 mars 2015 à 11h00, IPAG seminar room

For a year or more after a star is tidally disrupted by a black hole, debris can fall back at a rate that greatly exceeds the Eddington limit. Both observations and theoretical arguments indicate that mass loss is unable to regulate the rate at which matter is actually swallowed by the hole, leading to black hole growth rates and energy outputs that can exceed the Eddington limit by orders of magnitude. I will explain why regulation fails in such a case, and how this alternate mode of black (...)

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Séminaire IPAG de Giovani Strazzula (University of Catania), jeudi 26 mars 2015 à 11h00, IPAG seminar room

An important chapter of Astrobiology is to investigate the complexity of organic materials present in different space environments and the possibility they can be delivered on the early Earth as well as on other objects in the solar system and beyond, thus contributing to the chemical and biological evolution. Many experiments are conducted in several laboratories in the world, to understand the role of ion bombardment in producing complex chemical species after interaction with simple (...)

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Séminaire IPAG de Nirupam Roy (MPI Bonn), jeudi 2 avril 2015 à 11h00, IPAG seminar room

The interstellar medium is known to have significant density and velocity structures over a wide range of spatial scales. These structures are generally interpreted as the signature of turbulence in the interstellar medium. Radio astronomical observations are particularly useful to study two closely related aspects, the turbulence and the multiphase nature, of the interstellar gas. In this presentation, I will summarize some recent results from various observations, probing the interstellar (...)

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Séminaire IPAG de John Tobin (Leiden), jeudi 9 avril 2015 à 11h00, IPAG seminar room

Disks and multiple star systems are thought to form early in the star formation process. Conservation of angular momentum enables the formation of protostellar disks and protostellar companions can also form if the disk is gravitationlly unstable. However, theory and simulations have suggested disk formation and multiple star formation may be difficult due to removal of angular momentum by magnetic fields. Observations are now sensitive enough to begin testing these predictions and I will (...)

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Séminaire IPAG de Maria Jaqueline Vasconcelos (University of Brasília), jeudi 7 mai 2015 à 11h00, IPAG seminar room

Young, low mass stars present rotational periods that range from several hours to days. It is theoretically expected that stars that are surrounded by accretion disks rotate slower than diskless stars. However, observational results are controversial in this regard. In this work we present Monte Carlo simulations that evolve a population of stars from 1 Myr to 12.1 Myr. Each star has a mass from 0.3 M⊙ to 1.0 M⊙, a rotational period between 0.5 day to 18.5 days and an initial mass accretion (...)

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Séminaire IPAG de Sijme-Jan Paardekooper (University of London), jeudi 9 juillet 2015 à 11h00, IPAG seminar room

Planets are born in circumstellar discs of gas and dust. It has been known for more than 35 years that satellites embedded in gaseous discs can be very mobile. The discovery of Hot Jupiters, giant planets orbiting extremely close to their central star, showed that planets can indeed move away from their place of birth. However, incorporating migration in planet formation models has been far from trivial, since models predicted that inward migration should be extremely efficient, and (...)