Recent Talks

The new generation of spectrometers designed for extreme precision radial velocities enable correspondingly precise stellar spectroscopy. It is now fruitful to theoretically explore what the information content would be if stellar spectra could be studied with spectral resolutions of a million or more, and to deduce what signatures remain at lower resolutions. Hydrodynamic models of stellar photospheres predict how line profiles shapes, asymmetries, and convective wavelength shifts vary from disk center to limb. Corresponding high-resolution spectroscopy across spatially resolved stellar disks is now practical using differential observations during exoplanet transits, thus enabling the testing of such models. A most demanding task is to understand and to model spectral microvariability toward the radial-velocity detection of also low-mass planets in Earth-like orbits around solar-type stars. Observations of the Sun-as-a-star with extreme precision spectrometers now permit searches for spectral-line modulations on the level of a part in a thousand or less, feasible to test against hydrodynamic models of various solar features.

Planetary systems have been found systematically orbiting main sequence stars and red giants. But the detection of planets per se during the white dwarf phase has been more elusive with only 3 systems.  We have, however, ample indirect evidence  of the existence of planetary debris around these systems in the form of material acreted onto the white dwarf, disks and even planetesimals. In this talk, I will review how we can put the pieces together: how we can reconcile what we see in white dwarfs with what we can infer regarding the evolution of planetary systems from the main sequence phase.

Sunrise III es un observatorio solar diseñado para realizar observaciones epesctropolarimétricas a bordo de un globo estratosférico. Este observatorio cuenta con un telescopio de un metro de apertura que da luz a tres instrumentos posfocales principales: SUSI (Sunrise Ultraviolet Spectropolarimeter and Imager), SCIP (Sunrise Chromospheric Infrared spectra-Polarimeter) y TuMag (Tunable Magnetograph).

What is academic freedom? Why do we need it? What specific rights do we have as teachers and researchers? These questions are addressed in relation to the UNESCO 1997 recommendation for higher-education teaching personnel. It is observed that having good rules and regulations is one thing, what happens in practice often quite another. The final part of the talk lists the main current threats to academic freedom in the Western world and what can be done to counter them by efficient means, with a case study from Sweden.

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[English version below]

Extracto del Acta del Comité Director del IAC del 24 de noviembre de 2021:

“En relación con el seminario impartido recientemente en el IAC por el Prof. Erik J. Olsson (Univ. de Lund), la Dirección del centro lamenta profundamente que en el transcurso del mismo se realizaran afirmaciones absolutamente contrarias con nuestro firme compromiso con la igualdad de género y con los principios de nuestro Código Ético.

 Este profesor no se encontraba en visita de trabajo en nuestro centro. Su ponencia fue propuesta, de manera puntual, por un investigador del IAC a la Comisión de Seminarios, quien revisó el título y el resumen facilitados de la ponencia. Esta Comisión, por la información proporcionada, no podía deducir los contenidos totalmente inapropiados que finalmente fueron expuestos en varias transparencias y manifestados verbalmente por el referido ponente.

 La Dirección del centro expresa su rotunda desaprobación ante lo ocurrido y mantiene la medida de cancelar la distribución y el acceso a la ponencia a través de los medios de comunicación propios del centro; confirmando  la acción tomada, como medida preventiva por el Director, en el momento en el que se tuvo noticia de lo ocurrido.

 Se recuerda la responsabilidad que tiene todo el personal del centro con el cumplimiento de nuestro Código Ético, y los principios y fines del IAC en el desarrollo de nuestra actividad. Este compromiso es extensivo al personal externo que sea invitado para la realización de actividades en nuestro instituto.”

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[Text extracted from the acts of the Direction Committee meeting held on November 24th 2021]

"In relation with the seminar recently given by Prof. Erik J. Olsson (Univ. of Lund, Sweden), the IAC Direction deeply regrets statements made during that seminar since those statements fully oppose our firm committment towards gender equality and the principles of our ethical code.   

Prof. Olsson was not in an offical visit at IAC. His seminar had been proposed to the IAC's Seminar Commission by an individual senior researcher at IAC. This Commission revised the title and the abstract provided for this talk, from which it could not foresee the totally inappropriate content exposed in several slides, and verbally manifested by the speaker.

The direction of IAC expresses its absolute dissaproval of these events, and maintains its measure of blocking all institutional channels for the access and/or distribution of the recording of this seminar. Hereby we confirm that measure, which was adopted preliminarily by the IAC's direction when it was first informed of these events.

We remind all IAC staff of our responsibility towards the observation of our Ethical Code, together with the IAC's principles and objectives in the development of all our activities. This committment is extended to any external personnel that is present at our institution.”

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We will introduce several ways in which trivially embarrassingly parallel tasks can be run in laptops and desktops. We will introduce command-line tools such as GNU parallel and Kiko. We will then focus on simple techniques for optimisation of scientific computations in python. We will cover parallel computing with multiprocessing, acceleration of functions via numba, and GPU computing with cupy. The goal is to provide an easy roadmap for python code optimisation methods that can applied on already existing code, without writing a single line of C or FORTRAN.

In the aftermath of the cataclysmic explosion of massive stars, a vast zoology of source type is observed such as Supernova Remnants (SNRs), pulsar wind nebulae, pulsars and ‘zombie’ pulsars. Due to high velocity shock-waves combined with a high magnetic field or fast rotation in the case of pulsars, an efficient particle acceleration is achieved in those objects which are believed to be significant contributors to the pool of Galactic cosmic rays.
This seminar will start with a short introduction on particle acceleration and SNR physics, present the current scientific questions, and what we’ve learned from high-energy observations in the recent years.

On a more technical note, I will also present a new analysis method to fully exploit the multi-dimensional (X, Y, Energy) nature of X-ray data. This blind source separation method draws from the most advanced signal processing techniques to capture and disentangle the wealth of information contained in deep archival observations.

Zoom: 
https://rediris.zoom.us/j/86212537380?pwd=MGdYSE1rVDAyVlVESFE5RWEwOVlqZz09
Meeting ID: 862 1253 7380Passcode: 431670

YouTube: https://youtu.be/YwuCrGmp9_w

The phenomenon of magnetic reconnection in a magnetized plasma has been a subject of numerous studies over the past several decades in a variety of contexts, from high energy astrophysics, to solar and space physics, to laboratory-based experiments.  However, most magnetic reconnection studies have been devoted to exploring different collisionality regimes in a fully ionized single specie plasma.  Until recently, the physics of magnetic reconnection in partially, and weakly, ionized plasmas has received relatively little attention.  In this talk, I will provide a brief overview of the physical effects that partial ionization of the ambient medium may introduce in the dynamics of magnetic reconnection, with a particular focus on the environment of the lower solar atmosphere.

During the past 50 years, we have witnessed humankind’s first good, detailed look at the planets in our known Solar System.  All of these advances built upon Earth-based telescopic observations.  We predict surface conditions on other Solar System bodies before spacecraft reach them for in situ study.  The dominant type of asteroid identified telescopically in the main asteroid belt is classed as a C-complex asteroid, likely the origin of many of the primitive carbonaceous chondrite meteorites.

In the visible spectral region, one prominent, identifying spectral feature indicating the presence of Fe2+ → Fe3+ in clay minerals is located near 0.7 µm in over half of the C-complex asteroids.  Using its spectral presence, we can constrain the presence and thermal history of these objects in the Solar System.  I will describe the feature, and the implications of the evidence of its presence.  As an illustration, I will then show how we can use the presence of this feature to probe Solar System developmental history through examining the spectra of the jovian outer irregular satellites.

La experiencia en la compensación de los efectos de la turbulencia atmosférica le permitió al IAC desarrollar el sistema de control de la OGS y demostrar las comunicaciones ópticas entre satélites y tierra, poniendo a la ESA por delante de la NASA en este campo. Gracias a esto, el IAC consiguió contratos de la ESA en competencia abierta relacionados con las comunicaciones ópticas en el espacio. Pero España no participa en el nuevo programa de la ESA para financiar estas actividades, impidiendo al IAC presentarse a nuevos contratos. No obstante, la financiación conseguida de los fondos de recuperación para comunicaciones ópticas en el espacio nos está permitiendo mantener actividades.

En paralelo, aprovechando el desarrollo de la OGS, el IAC empezó a realizar experimentos de estrellas guía láser (LGS) de Na para óptica adaptativa, con el objetivo final de desarrollar la LGS para GTC. Posteriormente se firmó un acuerdo con ESO para realizar experimentos en el OT y ORM con la última tecnología de láseres de Na, tecnología que ha hecho viable lanzar el proyecto de LGS para GTC, dentro del principal programa actual en el Área de Instrumentación. La renovación del acuerdo con la ESO nos está permitiendo participar en nuevos experimentos que aplican la LGS en las comunicaciones ópticas en el espacio