Seminars and Colloquia at ESO/Santiago

For ESO and ESO-related Conferences and Workshops in Europe and Chile please check the main Conferences and Workshops page.


Broadcast of the ESO talks is available upon request.  If anyone is interested, kindly contact us via email
at least 30 min prior  to the beginning of the talk.


April 2014

16.4.14 (Wednesday)
15:30
"IP Eri and the formation of long-period eccentric binaries with a helium white dwarf"
Lionel SIESS (Universite Libre de Bruxelles, Belgium)
Abstract
Close
"IP Eri and the formation of long-period eccentric binaries with a helium white dwarf"

Lionel SIESS (Universite Libre de Bruxelles, Belgium)

Abstract

The recent discovery of long-period eccentric binaries hosting a He-WD or a sdB star has been challenging binary-star modelling. Based on accurate determinations of the stellar and orbital parameters for IP Eri, a K0 + He-WD system, we propose an evolutionary path that is able to explain the observational properties of this system and, in particular, to account for its high eccentricity (0.25). Our scenario invokes an enhanced-wind mass loss on the first red giant branch (RGB) in order to avoid mass transfer by Roche-lobe overflow, where tides systematically circularize the orbit. We explore how the evolution of the orbital parameters depends on the initial conditions and show that eccentricity can be preserved and even increased if the initial separation is large enough. The low spin velocity of the K0 giant implies that accretion of angular momentum from a (tidally-enhanced) RGB wind should not be efficient.
23.4.14 (Wednesday)
15:30
"Periodic variable stars of type A and B"
Nami MOWLAVI (University of Geneva, Switzerland)
Abstract
Close
"Periodic variable stars of type A and B"

Nami MOWLAVI (University of Geneva, Switzerland)

Abstract

The talk is centered on the discovery of a new class of main sequence periodic variable stars, located in the Hertzsprung-Russell diagram in the region between delta-Scuti and Slowly Pulsating B stars. I will present their discovery and discuss their possible origin.
24.4.14 (Thursday)
12:00
"The puzzling origin of magnetism in higher-mass stars"
Jason GRUNHUT (ESO Garching)
Abstract
Close
"The puzzling origin of magnetism in higher-mass stars"

Jason GRUNHUT (ESO Garching)

Abstract

The presence of magnetic fields in a small subset of main sequence intermediate-mass (A and late B-type) stars has been well-known for over 60 years. In the last 10 years, a new generation of spectropolarimeters has furthered our knowledge with the systematic discovery of magnetic fields among the pre-main sequence progenitors of the A and B-type stars (the Herbig Ae/Be stars) and among high-mass stars (main sequence early B and O-type stars). It is now well-established that ~10% of all stars with radiative envelopes (spanning ~1.5 decades of mass and at different evolutionary phases) host strong (surface polar field strengths of ~1 kG), stable (on the order of at least decades), globally-order (mainly dipolar) magnetic fields despite the fact that these stars lack a significant convective envelope - a key ingredient in driving any contemporaneous dynamo that is believed to be responsible for generating magnetic fields in a large range of astrophysical objects. Despite all our knowledge about magnetism in these stars, the fundamental question regarding the origin of their magnetic fields is still highly debated. In this talk I will discuss several theories that endeavour to explain the origin of magnetism in these stars and the observational evidence that may or may not support these ideas, including preliminary results from several ongoing programs that try to address this fundamental question.
30.4.14 (Wednesday)
12:00
"Solving the puzzles of Milky Way"
Pawel PIETRUKOWICZ (Obserwatorium Astronomiczne Uniwersytetu Warszawskiego)
Abstract
Close
"Solving the puzzles of Milky Way"

Pawel PIETRUKOWICZ (Obserwatorium Astronomiczne Uniwersytetu Warszawskiego)

Abstract

Our location among billions of stars of our disky Galaxy makes the studies on its structure and evolution extremely difficult. Ongoing large-scale optical and infrared galaxy surveys, such as OGLE and VVV, are on a good way to find answers to key questions.

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