Recent Talks

 Gaia all-sky scanning and multi-epoch photometric and spectroscopic observations offer unprecedented opportunities to detect and characterise magnetic activity and rotation of low-mass stars. In the second Gaia data release, rotation period and rotational modulation amplitude for ≈150,000 low-mass stars were provided from the analysis of the first 22-month of data collection. The third Gaia data release, based on the analysis of the first 34 months of data collection, contains rotational modulation data for ≈500,00 low-mass stars and an activity index for ≈2 million low-mass stars, this latter derived from the analysis of the CaII infrared triplet (IRT) observed by the RVS instrument. These constitute the largest catalogues of magnetic activity and rotational period to date. Such a large number of all-sky measurements represents a gold mine for studies related to stellar rotation, magnetic activity, and mass accretion. The analysis of the period-amplitude diagram of the rotational modulation has already provided evidence of distinct magneto-rotational regimes in the early phase of stellar evolution and of rapid transitions between them. Such evidence challenges a dependence on rotation only and suggests an important role of the rotational history in the early phase of the magneto-rotational evolution. The activity index derived from the CaII IRT clearly show three regimes, confirming suggestions made by previous authors on much smaller datasets. For the first time, a dramatic change in the activity distribution is found for Teff < 3500 K, with a dominance of low activity stars close to the transition between partially- and fully-convective stars and a rise in activity down into the fully-convective regime.

More than 200 species have been detected in the interstellar medium (ISM), among them many molecules, radicals and ions, containing the −C≡N functional group. Both linear and branched isomers of propyl cyanide (PrCN; C 3 H 7 CN) are ubiquitous in interstellar space. To date, PrCN is one of the most complex molecules found in the interstellar medium. Furthermore, it is the only one observed species to share the branched atomic backbone of amino acids, some of the building blocks of life. Radical-radical chemical reactions in gas phase and on an ice model are examined in detail using density functional theory M062X/6-311++g(d,p) and ab initio methods CCSD(T)-F12//MP2. The reaction mechanism involves the following radicals association: CH 3 CHCH 3 +CN, CH 3 +CH3CHCN for iso-PrCN and CH 3 CH 2 +CH 2 CN, CH 3 +CH 2 CH 2 CN, CN+CH 3 CH 2 CH 2 for n-PrCN formation. Rate constants (see Figure 1) are also reported for gas phase association reactions. All reaction paths are exoergic and barrier-less in the gas phase and on the ice-model, suggesting that the formation of iso-PrCN and n-PrCN is efficient on the water-ice model adopted.

 Another molecule : acetaldehyde (CH 3 CHO) is ubiquitous in interstellar space and is important for astrochemistry as it can contribute to the formation of amino acids through reaction with nitrogen containing chemical species. Quantum chemical and reaction kinetics studies are reported for acetaldehyde formation from the chemical reaction of C(3 P) with a methanol molecule adsorbed at the eighth position of a cubic water cluster. We present extensive quantum chemical calculations by means of CCSD(T)//wB97XD/6-311++G(2d,p) for total spin S=1 and S=0. The rate limiting step for forming acetaldehyde is the C–O bond breaking in CH 3 OCH to form adsorbed
CH 3 and HCO. We find two positions on the reaction path where spin crossing may be possible such that acetaldehyde can form in its singlet spin state.

1. I. BenChouikha, B. Kerkeni, et al. “Quantum chemical study of the reaction paths and kinetics of acetaldehyde formation on a methanol-water ice model”, ACS Adv., 12,18994 (2022).
2. B. Kerkeni, V Gámez, G. Ouerfelli, M-L. Senent, and N. Feautrier “Understanding Propyl-cyanide and its isomers Formation: Ab initio Study of the Spectroscopy and Reaction Mechanisms.”, Mon. Not. Roy. Astron. Soc. https://doi.org/10.48550/arXiv.2301.12297 (2023).

Globular clusters (GCs) are one of the oldest stellar systems where individual stars could be resolved and are essentially the fossils of galaxy formation. Understanding their internal evolution is crucial for formation and evolution of the host galaxies as well as, to interpret their present-day structural and kinematical properties. The dynamical evolution of these collisional systems is significantly affected by properties such as binary fraction, concentration, tidal field of the galaxies and so forth. As a result, GCs with the same chronological age can be in very different dynamical evolutionary stages, making the determination of their "dynamical age" observationally challenging. 

In this talk, I will be presenting new empirical parameters measurable from observations which are able to trace the different phases of dynamical evolution of star clusters. I will also discuss the impact of heating sources such as, primordial binaries and stellar mass blackholes on the dynamical evolution and in-turn on the new empirical parameters.

Presentación con altas probabilidades de fracaso, en la que se hará una pequeña demostración práctica de cómo funciona el lazo de control de óptica adaptativa (AO) del instrumento GTCAO. Después de una pequeña introducción de las funcionalidades provistas por el lazo control de AO, se mostrará el funcionamiento real observando una estrella simulada con el sistema de calibración del propio instrumento, con diferentes condiciones atmosféricas. La operación del instrumento, actualmente instalado en la Sala de Rotadores de AIV, se realizará desde el Aula.

Youtube

https://youtu.be/fd_iuU8XAW8

What would a 35m-scale narrow field-of-view telescope look like that is designed for high dynamic range direct imaging science? The EU has charged the IAC in a 5 year program to explore and develop the concepts and technologies that could make such a ground-based telescope possible. From tensegrity mechanics to astrophotonic wavefront sensing and control in Fizeau optics, the IAC and IACTEC "Laboratory for Innovation in Optomechanics (LIOM)" is just now starting these research activities. This talk will outline the motivation, concepts, and prototypes that LIOM and the IAC will advance over the next few years.

Sabemos que la música lleva con nosotros desde la prehistoria y ha ido evolucionando con el pasar de los años hasta convertirse en lo que conocemos y practicamos a día de hoy. Pero, ¿es acaso que descubrimos un "lenguaje universal" como la llaman algunos o no es más que una argucia armónica que inventamos para complacer a nuestros sentidos? Esta charla presenta un análisis matemático de las características armónicas de la música a través de las distintas etapas que ha atravesado con el pasar de los siglos, con demostraciones experimentales y ejemplos auditivos.

YouTube:

https://youtube.com/live/FoCzHnHWTwY?feature=share

Understanding stellar structure and evolution significantly impacts our understanding of the tight-knit evolution of galaxies and exoplanet systems. However, hidden behind the luminous layers of the stellar atmosphere, the deep interior of a star is eluding from direct measurements. The seismic study of waves propagating the deep interior provides the only way to measure the internal structure, dynamics, and mixing in any given star and compare it to theoretical models.

With the photometric data from space missions, such as the NASA Kepler telescope, a golden age has begun for seismology. In particular, the seismic studies of thousands of solar-like have led to numerous breakthroughs in our understanding of the stellar structure of red-giant stars. Complimentary information on stellar binarity, tidal forces, rotation, and lithium abundance provide additional constraints to characterize the advanced evolution of stars further and provide high-resolution insights into complex internal adjustments. Approaching a sample of ~1000 identified solar-like oscillators in binary systems, provided by the ESA Gaia and NASA TESS missions draws an exciting picture on the interaction of stellar and orbital evolution.

https://rediris.zoom.us/j/89275150368?pwd=QnNxc09KbmJMTmdaRmVGdjZYSlBqdz09
ID de reunión: 892 7515 0368

Código de acceso: 101169

https://youtube.com/live/6Iproe6Zwb4?feature=share

We divide this talk into two parts. In the first part, we will introduce the numerical codes we use, mainly in solar physics, to infer information about the solar atmosphere from spectro-polarimetric observations. In particular, we will present a new version that was recently developed (see Ruiz Cobo et al., 2022). In the second part of the talk, we will learn how we opted to bring the code to the public through online tutorials, and we will show where to find them (see the link below). Also, we will explain why we believe this new approach could be interesting for other research areas and give some tips in case someone is interested in trying the method.

The previous years have witnessed a big leap forward in our understanding of the Milky Way. Thanks to the highly accurate astrometry and photometry provided by the Gaia mission in combination with large photometric and spectroscopic all-sky surveys, we have now a clearer view of the chemo-dynamics of the stellar populations that constitute our Galaxy. Our former characterization of the Milky Way components (the bulge, halo, and thick and thin discs) is now compromised by the latest discoveries and their limits are blurrier than ever. However, hints on the kind of events and processes that led to the formation of our Galaxy emerge from the analysis of these high-quality data. In this talk I will review the latest results about what caused the current stellar halo configuration and the observational evidences of the dawn of the Milky Way’s disc. I will also present the project carried out at the ULL/IAC to derive the star formation history of the Milky Way which will provide the temporal information that is still missing in Galactic research.

https://rediris.zoom.us/j/85737198942?pwd=dG1lYmNVRjR3dzRGZFhldUhGRloyUT09
ID de reunión: 857 3719 8942

Código de acceso: 350472

https://youtube.com/live/i1KS2YngkMA?feature=share

Active galactic nuclei (AGN) are the most luminous persistent sources in the universe. A minority of AGN are characterised by powerful plasma jets extending from close to the supermassive black hole at the centre of their host galaxy up to megaparsec scales in the intergalactic space. Inside these jets, charged particles are accelerated to relativistic speeds and emit non-thermal radiation. In blazars one jet is oriented at a small angle with respect to the line of sight, and this causes Doppler beaming of the jet emission, with consequent flux enhancement, and decrease of the variability time scales. The dominant contribution of the jet radiation to the blazar emission makes these objects ideal sources to investigate what happens in the inner regions of AGN jets and even what is the jet structure and dynamics. We have been studying blazar variability for more than 20 years in the framework of the Whole Blazar Telescope (WEBT) Collaboration, including many tens of astronomers observing mainly in the optical, but also in the radio and near-infrared bands. The analysis of the wealth of multiwavelength data gathered during the WEBT monitoring campaigns, with unique time resolution in the optical band, allowed us to outline a model for the blazar variability, involving an inhomogeneous twisting jet. In the final part of the seminar we will mention the contribution to blazar understanding that is expected from Vera C. Rubin Observatory’s Legacy Survey of Space and Time.