Recent Talks

Series: XXVIII Canary Islands Winter School of Astrophysics: Solar System Exploration

Topic: Cometary Science and the Rosetta Mission.

Lecture 1: Comets and the Rosetta mission. 

Dr. Küppers gives a general overview on comets in the context of the formation of the Solar System, describing their physical, dynamical, and compositional properties. The speaker describes cometary missions that have been sent before the Rosetta mission and lists some of the most important cometary science questions that are still unsolved or under debated.

Series: XXVIII Canary Islands Winter School of Astrophysics: Solar System Exploration

Topic: Exploration of the Solar System by the European Space Agency

Lecture 1: Overview of ESA Solar System Missions 

Dr. Cardesin introduces in this talk the European Space Agency, describing the agency's structure, budget, and activites. Particular atention is paid to the ESA Science Program and to the role of ESAC (Madrid), with a description of all past, present, and future space missions in which the ESA has been/is/will be involved related to Solar System exploration.

Series: XXVIII Canary Islands Winter School of Astrophysics: Solar System Exploration

Topic: Physical Properties of Asteroid Surfaces

Lecture 1: Introduction to asteroid UV-VIS-NIR spectrometry

In this first talk, Dr. Muinonen gives an introduction to polarimetry, photometry, and spectropolarimetry techniques and their application to the study of asteroid surfaces. The talk includes a description of the Shkuratov radiative transfer model and the use of Monte Carlo simulations to model radiative transfer for meteorite spectra. 

Series: XXVIII Canary Islands Winter School of Astrophysics: Solar System Exploration

Topic: Exploring the Outer Solar System

Lecture 1: TNOs: a brief history, dynamical structure, and characteristics of its inhabitants

This first talk is devoted to provide an overview of the current state of the population of minor bodies beyond the orbit of Neptune. A review of the discovery history is given, as well as a description of the physical, compositionsl, and dynamical properties of trans-Neptunian objects (TNOs), Pluto, and the Kuiper belt in general.

Series: XXVIII Canary Islands Winter School of Astrophysics: Solar System Exploration

Topic: Planetary Atmospheres.

Lecture 1: Overview of planetary atmospheres in the Solar System. 

In this lecture Dr. Lebonnois talks about the large diversity of objects that populate our Solar System, gives an overview on the different types of atmospheres that can be found, as well as the atmospheric structures, and ends with an update on the current exploration of planetary atmospheres. 

We present new results concerning the radial gradients (Fe, alpha, s- and r-process elements) across the Galactic thin disk. We use young (t<300 Myr, classical Cepheids) stellar tracers for  which we collected high resolution spectra with UVES at VLT together with similar estimates avaialble in the literature. The investigated elements display well defined negative gradients when moving from the innermost to the outermost regions. Moreover, we also found that the radial gradients of the neutron capture elements are positive as a function of age (pulsation period). Thus suggesting an age dependence similar to alpha-elements. On the other hand, the slopes of [elements/Fe] vs Galactocentric distance are more positive than for alpha-elements. We discuss plausible working hypotheses to take account of the difference, and perform a detailed comparison with similar abundances for dwarf and giant stars available in the literature. We also discuss the abundance ratio between s- and r-process elements (La/Eu) and between heavy and light s-process elements (La/Y)  and outline their impact on the chemical enrichment history of the Galactic thin disk. Finally, we present new results concerning the iron gradient of the Galactic halo using old (t>10 Gyr, RR Lyrae) stellar tracers for which we collected high-resolution spectra  with UVES at VLT together with metallicity estimates based on low-resolution spectra available in the literature. We discuss the difference with the metallicity gradient and spread in metallicity of the M31 halo and the impact on their early formation and evolution.

The small source class of gamma-ray binaries consists at present of six known objects with different orbital periods ranging from days up to several years. One of the best studied gamma-ray binary across all frequencies, LS I +61 303, is highly variable at any given orbital phase and was lately discovered to show on top of orbital also superorbital variability at high energies. In contrary, the other famous binary, LS 5039, shows no variations apart from those related to the orbital period. The other unresolved mystery in most of these sources is the nature of their compact object. Both neutron star (e.g. PSR B1259-63) and probable black hole (microquasar, e.g., Cyg X-3) binary systems have been detected at GeV energies, hence both types of compact object are viable in the undetermined systems. In this talk I will present the recent findings on the known gamma-ray binaries up to now and discuss their behavior at high and very high energies.

Global snow and ice cover (the "cryosphere") plays a major role in global climate and hydrology through a range of complex interactions and feedbacks, the best known of which is the ice - albedo feedback.  Snow and ice cover undergo marked seasonal and long term changes in extent and thickness. The perennial elements - the major ice sheets and permafrost - play a role in present-day regional and local climate and hydrology, but the large seasonal variations in snow cover and sea ice are of importance on continental to hemispheric scales. The characteristics of these variations, especially in the Northern Hemisphere, and evidence for recent trends in snow and sea ice extent are discussed.

Galaxy clusters are the most massive gravitationally collapsed structures in the universe, and they have important cosmological and astrophysical applications. Measurements of the radial distribution of galaxies in clusters show how galaxies trace the underlying dark matter distribution, and provide constraints on the physics related to their evolution in these environments. I will present measurements on the radial distribution of galaxies in two cluster samples, which span about 8 Gyrs of lookback time. By matching local galaxy clusters to their progenitors at high redshift, we study how clusters assemble their stellar mass content. Interestingly, this suggests that the central part of the stellar mass distribution of local galaxy clusters is already in place at redshift, and any further growth seems to happen in an inside-out fashion. I will put these findings into context by comparing them to the results from dark matter simulations. I will also focus on the abundance and spatial distribution of ultra-diffuse galaxies (UDGs, which have the luminosities of dwarfs but sizes of giant galaxies) in clusters. These mysterious galaxies have been found to be surprisingly abundant in local clusters, but their origin remains puzzling. I will discuss what we can learn about the properties of UDGs by studying their abundance as a function of halo mass, and their radial distribution in these haloes.

Approximately 10 per cent of massive OBA main-sequence (MS) and pre-MS stars harbour strong, large-scale magnetic fields. At the same time, there is a dearth of magnetic stars in close binaries. A process generating strong magnetic fields only in some stars must be responsible and several channels for the formation of magnetic massive stars have been proposed. In this talk, I will present recent results on the origin and evolution of such strong surface magnetic fields. Regarding the origin, mergers of MS and pre-MS stars have been proposed to form magnetic stars and I will highlight a method to probe this hypothesis observationally. Applying this new method to two magnetic massive stars, we find that they are indeed consistent with being MS merger products. Utilising a large sample of magnetic and non-magnetic OB stars, I will show that there is a dearth of evolved magnetic stars that suggests that magnetic fields disappear over time. I will argue that this is most likely caused by decaying magnetic fields.