Recent Talks

The majority of massive stars are born in close binary systems with orbital periods of a few days. At some point during their core-hydrogen burning phase, both members of these close binaries inevitably overflow their Roche lobes simultaneously and get bound by a common equipotential surface. The characteristics of this `contact phase’ will determine the fate of the binary system: whether the stars will merge on the main sequence or evolve further towards becoming potential gravitational-wave progenitors. Although data is available for several of these massive contact binaries in the Magellanic Clouds and the Milky Way, there has not been a dedicated study of these systems so far. In this talk, I will present the first set of detailed binary models covering a wide range of initial masses (20-80 Msun) and initial periods (0.6-2 days), focusing especially on the properties of the contact phase. We find that our models can approximately reproduce the period-mass ratio trend of the observed binaries although for the higher masses of our grid, our model predictions do not match with what is observed. We also find that those binary models which are in contact over nuclear timescales evolve towards equal masses before ultimately merging on the main sequence. This first study of massive contact binaries has allowed us to gain insights into the physics of massive contact systems and also provide reasonable predictions for the final fate of close massive binary stars.

Durante este seminario se hará un recorrido sobre la instrumentación dentro del proyecto QUIJOTE, desde de los instrumentos ya existentes y su problemática hasta el estado actual de los instrumentos de nueva generación y los posibles desarrollos a futuro.

In this talk, I will start by briefly presenting the Institut d'Optique Graduate School and the Laboratoire Charles Fabry, where I conduct my research. Then I will explain the principle of adaptive optics and discuss some issues related to the control of AO systems. This will lead to the general ideas behind high-performance control. In particular, I will explain why high-performance control can outperform the standard integrator. Some results of on-sky experiments will be shown, and I will conclude the talk by presenting our PhD students working through research collaborations.

Al objeto de incrementar la cobertura de cielo proporcionada por el sistema de óptica adaptativa de GTC, durante los últimos 4 años se ha estado trabajando en la incorporación de un sistema de estrella guía láser de Sodio. A través de esta charla se repasará el estado actual del proyecto enfatizando aquellos aspectos relacionados con el sistema óptico de lanzamiento de la estrella guía. 

In two previous talks we covered the basics of Git (http://iactalks.iac.es/talks/view/1426) and some intermediate concepts (http://iactalks.iac.es/talks/view/1428). In this one we will focus on more advanced features that can make your Git experience much more productive and efficient.

First we will focus on a very common collaboration "procedure", which we didn't have time to cover in any detail in the "Intermediate Git" talk, namely "Pull requests". 

Next, since most of your work with Git will be on local repositories, we will see some more advanced commands and features, such as pull requests, rebase, reset, hunks, reflog, stash and blame.

While this series on Git doesn't cover everything there is to Git, it does cover almost all you'll need to become a regular Git user.

Globular clusters (GCs) are fascinating objects nearly as old as the Universe that provide insight on a large variety of astrophysical and cosmological processes. However, their formation and their early and long-term evolution are far from being understood. In particular, the classical paradigm describing GCs as large systems of coeval stars formed out of chemically homogeneous material has been definitively swept away by recent high-precision spectroscopic and deep photometric observations. These data have provided undisputed evidence that GCs host multiple stellar populations, with very peculiar chemical properties. In this talk, I will review the properties of these multiple populations, before presenting the different scenarios that have been proposed to describe their formation. I will focus on the (many) current theoretical issues and open questions. 

This talk will give an overview of the resources for scientific computing at the IAC. The network, los burros, and LaPalma will be described, together with the basics for using them and practical examples. 

Speakers: Ana Esteban, Carlos Allende, Isaac Alonso and Juan Carlos Trelles (IAC)

HORUS (High ResolUtion Spectrograph) es un espectrógrafo de alta resolución, instrumento visitante en GTC y disponible para la comunicad científica desde prinicipios de 2019. Instalado en la plataforma Nasmyth B, detrás de OSIRIS, comparte foco con él. En esta charla se describe su software de control, resaltando la implementación realizada para ser un instrumento visitante de GTC y cómo se ha resuelto el problema del apuntado de un objeto.

IAC leads the extragalactic ESO Public Survey SHARKS (Southern H-ATLAS Regions Ks band Survey; PI: H. Dannerbauer). We survey with the ESO 4m telescope VISTA and the near-infrared camera VIRCAM more than 300 square degrees at 2micron with the near-infrared filter K_s, reaching a depth of K_s~22.7 (AB) with 1200 hours of observations. The covered fields have been previously observed with the infrared space telescope Herschel. Optical coverage already exists from the Dark Energy  Survey and the Hyper Suprime-Cam Subaru Strategic Program. In the future, these fields will be observed with the SKA-precursor ASKAP, EUCLID, LSST and eROSITA. Thus due to its exquisite multi-wavelength coverage, this dataset has a huge legacy value. The principal aims of the survey are: i) to search for counterparts of infrared and radio-selected sources, ii) to study the evolution of the most massive structures in the Universe and iii) to produce a sample of a thousand strong lenses for cosmography studies. Nonetheless, given its sensitivity and wide-area coverage in the near-infrared, it represents an excellent data-set for a wide range of astrophysical studies beyond their initial objectives, including the study of ultracool dwarfs in the Milky Way and high-redshift quasars. Currently, we are preparing the first public data release (DR1) of SHARKS at ESO. In this talk I will introduce the science that can be done with SHARKS. Finally, I will present the current status of the project, including a first look up at the DR1, and try to encourage the community to exploit this outstanding dataset.

Following up on our previous "Git version control system basics" seminar (https://bit.ly/35CCX7k), the focus of this talk will be to learn the features of Git that will allow us to collaborate with other colleagues. For this, the main concepts needed are branch merging (including merges with conflicts), remote repositories and hosted repositories (GitHub, GitLab, Bitbucket, etc.). 

Thanks to the distributed structure of Git, collaboration with colleagues can become very efficient (allowing for many different workflows) and it avoids the single point of failure of centralized version control systems, but its complexity also goes up. Properly understanding the concept of remote repositories makes collaboration with Git straightforward.

Other Git features and tools that are not essential, but that will make Git usage much more effective and powerful (like stash, rebase, pull requests, etc.) will be left for a planned "Advanced Git" follow-up talk.