Colloquia

The ESAC Science Data Centre (ESDC) hosts the scientific  archives from the astronomy, planetary, heliophysics, and human and  robotic exploration missions from ESA. In particular, at the ESDC we host mirrors of the Hubble Space Telescope and the James Webb Space Telescope archives, as well as the main archives for many other astronomy missions such as Planck, Herschel, XMM-Newton and Euclid. These archives represent more than three decades of space‑based astronomy and their science archives offer tremendous potential for new discoveries. In addition to the archives, at the ESDC we have developed ESASky (sky.esa.int), a web application to discover astronomical data from ESA and other partner agencies and ground based observatories, and ESA Datalabs, a science platform that allow users to discover, access and analyze the data from these missions  on premises, without the need to download anything. In this presentation I will show how users of the eHST, eJWST and Euclid Data Space can take advantage of ESASky and ESA Datalabs science platform to implement and execute end‑to‑end research workflows. This is possible thanks to two very intuitive user interfaces that combine search tools to discover the  data from HST, JWST and Euclid,  analysis and calibration software for the case of JWST, and the necessary computational resources, all in the same data centre.

Scientific coffee will be served in the cafeteria at 12:30 BEFORE THE SEMINAR

Dozens of gravitationally self-bound stellar groupings are known to orbit the halo of the Milky Way. At the faint end, some of these satellites are globular clusters: compact (few pc size), chemically homogeneous systems whose internal dynamics show no evidence for dark matter. Others, on the other hand, are dwarf galaxies: typically larger (~kpc size) systems with varied stellar populations and internal kinematics suggestive of the presence of large amounts of dark matter.  More recently, a number of satellites with properties straddling these two categories have been identified: they are compact in size, but fainter than traditional globular clusters or dwarf galaxies, and with velocity dispersions so low that only upper limits can be placed on their dark matter content. I will discuss the cosmological significance of these systems for the clustering of dark matter in the smallest scales, and for our understanding of the formation of the faintest galaxy systems in the Universe.

Asteroids preserve key records of the Solar System’s history, providing insights into collisional and surface evolution as well as the origins of water and life on Earth. Among them, Near-Earth Asteroids (NEAs), with perihelion distances smaller than 1.3 au, represent a unique population that enables detailed investigations of the secular evolution of their orbits and spin states. They are also crucial targets for future spacecraft exploration, planetary defense, and potential space resource utilization. In this talk, I will introduce recent observational studies of NEAs conducted during close approaches to Earth within a few lunar distances, where otherwise impossible observations become feasible. These include simultaneous tricolor video photometry of sub-minute rotators, as well as archival-data studies of an asteroid that will soon approach Earth closely enough to become a spatially resolved target.

B-type stars have temperatures ranging from 10000 to 30000 Kelvin and masses between 3 and 20 Mo. They exhibit radiation-driven stellar winds that lead to significant mass loss throughout their evolution, influencing the chemical enrichment of the interstellar medium. A key feature of this stellar group is its high degree of heterogeneity, including a wide variety of peculiar objects such as stars with high rotational velocities, circumstellar envelopes, or chemical anomalies (e.g., Be, B[e], HAeBe, and LBVs). In these cases, determining fundamental parameters like effective temperature (Teff)  and surface gravity (logg) is particularly challenging, as both line intensities and profiles can be strongly affected by circumstellar material or rotation.

An alternative and robust methodology for estimating these parameters is the BCD (Barbier-Chalonge-Divan) Spectrophotometric Classification System. Based on the analysis of the Balmer discontinuity (or Balmer jump) at 3700 Å, this method was developed as a quantitative equivalent to the MK and Yerkes systems using measurable observable parameters. The BCD system offers a straightforward approach to determining Teff and logg, even in stars with prominent emission lines, while also providing independent estimates of color excess and distance.

In this seminar, I will discuss the application of the BCD method to a diverse sample of objects, ranging from B-type stars in open clusters to emission-line stars and objects in transitional evolutionary phases, such as sgB[e], LBV, and HAeBe stars.

The implementation of Adaptive Optics at the GTC, combined with the science instrument FRIDA -- an imager and integral field spectrograph operating in the near-infrared —- represents a factor of 10 to 15 improvement in angular resolution compared to current or planned GTC instruments. These resolutions are still a factor of 1.5 to 4 better than those achieved by the finest space telescopes, JWST and HST. This presentation highlights the imminent realisation of these capabilities at the GTC and the unique scientific opportunities enabled by the GTC+AO+FRIDA combination. To this end, I will outline possible science pathways that are uniquely possible with GTC+AO+FRIDA, ranging from stellar surface mapping to studies of the Local Group at the finest spatial scales and the high-redshift Universe.

The aim of this presentation is to introduce the research I have carried out in recent years, which led to being awarded a Ramón y Cajal fellowship, and to outline the future goals of the project. I will cover the three main pillars of my work: the analysis of spectropolarimetric observations, the use and development of inversion codes (computational tools used to infer the physical parameters of the solar atmosphere from these observations), and the design of state-of-the-art instrumentation for ground-based, balloon-borne, and space telescopes. All of these efforts serve a common purpose: advancing our understanding of the Sun. Thus, I will also touch on some of the most compelling open questions in solar physics I have worked on, including the nature of quiet Sun magnetism and the energy release mechanisms behind solar flares.

 The fate of massive stars and the type of supernova (SN) they produce are closely linked to their final stages of evolution. During these late phases, stars may undergo episodic mass loss, forming circumstellar material (CSM) that can leave observable signatures in the SN spectra, particularly as resonance lines in the near-ultraviolet (NUV). In this talk, I will present a sample of superluminous supernovae (SLSNe), an exceptionally luminous class of SNe, focusing on the NUV spectroscopy to search for signatures of recently ejected CSM shells. I will first discuss two SLSNe in which CSM shells are detected, inferring their properties and the timing of the ejection, along with implications for the underlying mass-loss mechanisms and progenitor systems. I will then extend the analysis to the full sample, modelling the spectral regions where CSM-related features are expected in order to evaluate how common such mass-loss episodes are and to place constraints on undetected CSM shells. These results provide new insights into the final stages of massive star evolution and help constrain the nature of SLSN progenitors.

Supernovae are usually cast as efficient dust destroyers. I will show that, when realistic environments are taken into account, they instead emerge as net dust enrichers. Combining 3-D hydrodynamic simulations with semi-analytic cooling and cloud-crushing calculations, I follow dust processing from ejecta and wind-blown bubbles to dense circumstellar shells, dusty clumps, and sequential supernovae in compact star clusters. Across these environments, rapid radiative cooling often limits dust destruction, and in dense shocked clumps can even open a path to further growth. The result is a consistent picture in which supernovae inject and build up dust in remnants, superbubbles, and star-forming clouds. On cluster scales, the key question then becomes retention: how much of that dust remains in the system, and how much is vented out by clustered explosions. This may help explain both the low retained dust content inferred for Blue Monsters at z>10 and the emergence of dustier systems by z≤8, all within the first few hundred million years of cosmic time.

We are delighted to welcome F. Duncan Haldane, winner of the Nobel Prize in Physics, for a very special seminar.

The study of “topological states” in quantum condensed matter has been very active in recent years. Though it was initially discovered over 45 years ago, the quantum Hall effect continues to reveal new surprises and is at the heart of quantum topology, expecially in its “fractional” presentation.

*After the colloquium, a science coffee will be served in the cafeteria.