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.


August 2014

26.8.14 (Tuesday)
12:00
"Atomic Data Calculations at Queen's University Belfast"
Kanti M. AGGARWAL (Queen's University Belfast)
Abstract
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"Atomic Data Calculations at Queen's University Belfast"

Kanti M. AGGARWAL (Queen's University Belfast)

Abstract

In this seminar atomic data (namely energy levels, radiative rates, life-times, electron impact excitation collision strengths, and rate coefficients) will be discussed for a variety of ions, which have applications in modelling and diagnostics of solar and other astrophysical plasmas. These results are theoretical from the fully relativistic GRASP (General purpose Relativistic Atomic Structure Package) and DARC (Dirac Atomic R-matrix Code) programs. The difficulties of performing large calculations, and importance of including relativistic effects and resonances in the determination of excitation rates will be highlighted. Comparisons will be shown and discrepancies with other available data will be discussed. Results will specifically be presented from our recent calculations on Al X, Si II and Fe XIV. The difficulties of assessing the accuracy of atomic data will also be emphasized.
28.8.14 (Thursday)
12:00
"Characterization of debris disk in direct imaging and high angular resolution "
Julien MILLI (ESO, Chile)
Abstract
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"Characterization of debris disk in direct imaging and high angular resolution "

Julien MILLI (ESO, Chile)

Abstract

To shed light on the formation and evolution of planetary systems, I will present an observational approach based on the study of debris discs. These circumstellar discs are composed of dust particles constantly generated by collisions of small rocky bodies called planetesimals, orbiting a main-sequence star. The stellar light they scatter can be studied from the Earth and reveal a wealth of information on the architecture of the system. These observations are challenging because of the high contrast and the small angular separation between the disc and the star. The recent developments of new high-contrast instruments with extreme adaptive optic systems are therefore bringing new expectations for the study of these systems. In this talk, I will present the characterization of two debris discs thanks to two instruments installed on the Very Large Telescope: NaCo and SPHERE (Spectro Polarimetric High contrast Exoplanet REsearch). NaCo has been in operation for more than a decade and has undergone many improvements. SPHERE has been designed and assembled in the same period, was intensively tested in laboratory in 2013, and is currently being commissioned on the telescope. In the first part, I show why a detailed understanding of the behaviour of the instrument is crucial to detect and characterize disks in scattered light. I quantify in particular the performances, advantages, and biases of the angular, polarimetric and reference-star differential imaging technique. In a next step, I apply those techniques to characterize two prototypes of debris discs, around the stars β Pictoris and HR 4796A. A detailed analysis of the morphology is carried out, which reveals new asymmetries interpreted in terms of gravitational perturbers or of dust scattering properties.

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