Recent Talks

Understanding the abundance patterns of metal-poor stars and the production of heavy elements through various nucleosynthesis processes offers crucial insights into the chemical evolution of the Milky Way. We investigate the origins of light, alpha, Fe-peak, and r-process elements in metal-poor halo stars using data from the R-Process Alliance observed by the Gran Telescopio Canarias (GTC). Our analysis of these faint stars reveals intriguing patterns. We utilize the abundances of carbon, Fe-peak elements and the alpha-elements to probe the contributions from different nucleosynthesis channels in the progenitor supernovae. Additionally, we identify globular cluster stars at very low metallicity, which adds to the growing evidence of a lower metallicity floor for GCs. We also reveal differences in the trends of the neutron-capture element abundances from the RPA data releases, which provide constraints on their nucleosynthesis sites and subsequent evolution. Complementing this, we use early data from the new dual-fibre high-resolution spectrograph GHOST at Gemini South to study globular clusters. We identify first and second-generation stars in the metal-poor globular cluster NGC 2298 through light element anti-correlation, obtaining precise abundances for over 45 elements, including 20 neutron-capture elements up to thorium. A larger dispersion in n-capture and Fe-peak elements is observed among first-generation stars, along with variations in the universal r-process pattern. Increases in Sr and Ba with Mg, significant trends in light, alpha, and Fe-peak abundances, and correlations between light and r-process abundances are noted. These findings enhance our understanding of the Milky Way's chemical evolution by integrating data on metal-poor stars and globular clusters, elucidating the nucleosynthetic pathways shaping our Galaxy's elemental composition.

Using only the speckle pattern of an unresolved source in the image-plane, it is possible to reconstruct the pupil-plane wavefront for use in an adaptive optics loop using Deep Neural Networks.  My thesis has involved exploring and refining this technique with applications from real time correction of the atmosphere for ELF telescopes, to sensing residual, non-common-path aberrations in coronagraphic instruments -- where dedicated WFS hardware becomes much more challenging.  I will present some background and results of both simulated as well as successful on-telescope testing.  Further, I may spend a bit of time on my recent exploration into using Deep Reinforcement Learning: its uses in bridging the sim-to-real gap, and for solving problems where exact solutions aren't available.

Seminarios Investigacion le está invitando a una reunión de Zoom programada.

Less than 30 years ago, we did not know whether planets exist outside our solar system. Fast forward to 2024, astronomers have discovered well over 5000 planets orbiting other stars similar to our Sun, including some that may have the right conditions to host life. As we learned that the formation of planets seems to go hand-in-hand with the birth of stars, we begin to wonder:

•     What happens to planetary systems when their host stars run out of fuel, and turn into Earth-sized white dwarfs?
•     Are those systems, if they exist, detectable?
•     What will happen to our solar system, and to the Earth?
•     And what are the possible implications for life?

I will discuss the late evolution of planetary systems, the observational fingerprints of planets and their debris orbiting white dwarfs, and how studying these exotic systems  improves our general understanding of the formation of planets.

With the detailed measurements available for our Galaxy and the local volume, the Milky Way and its satellites are a unique laboratory for the galactic archaeology field, which is trying to reconstruct the galactic evolution history from fossil records. In this context, spectroscopy is one of the primary tools to explore the physics of the Universe. This field, encompassing a wide range of subjects from detecting exoplanets to studying the expansion of the Universe, has begun collecting massive data-sets, yielding remarkable outcomes. Among the various applications of spectroscopy, the study of stellar abundances is of primary importance. In fact, the chemical information enclosed in a stellar spectrum is extremely informative, as galactic chemical evolution tells us that elemental abundance ratios can be used to trace star formation history between stellar generations. This holds true for both our galaxy and its satellites. My talk will be about the application of stellar spectroscopy to investigate chemical evolution. I will present a spectroscopic dataset that I assembled to characterise the stellar populations of the Sagittarius dwarf spheroidal galaxy. Additionally, I’ll explore the potential (and limitations) of chemical tagging a subject I've investigated using various spectroscopic datasets. Despite their diversity, the common aim is to understand the most effective ways to use stellar spectroscopy and chemical abundance ratios for retracing the chemical evolution within distinct galactic environments. 

The intensity interferometry technique enables telescopes to achieve exceptionally high angular resolutions, on the order of hundreds of microarcseconds, in the optical range. I will explain how, in contrast to traditional phase interferometry, this technique readily accommodates blue and near UV wavelengths, and is straightforward to expand to longer telescope baselines with the potential to reach angular resolutions of a few microarcseconds for baselines of a few kilometers. In addition to its regular gamma-ray observations, we have been operating MAGIC as an optical interferometer for several years. We have recently measured the diameters of 13 early-type stars that lacked prior measurements. In addition, in 2024 we have extended the same technical solutions to the first CTA Large-Sized Telescope operating at ORM, LST-1. I will present these observations, delineate plans for the upcoming upgrades to the four LSTs currently under deployment, and describe a science cases that are within reach during the next few years, among others the study of early type stars, fast rotators, and expansion of novae.

Black Holes are for most of their life in a dormant state, and yet, just a small amount of accreted mass would be needed for them to trigger the most luminous Quasars. We find however that there is plenty of matter ready to fall into the accretion disc in most galactic nuclei, why then are most of them fainter than expected?
I will discus the ubiquity of dust and molecular gas in the central parsec of galaxies. This dust and gas often form a nuclear spiral of filaments, which may slow down inflow towards the centre. Using multiwavelength, parsec-scale and JWST data collected by our group for low activity Black Holes I will show a first evidence for a cold Quasar-like accretion disc, and that the main channel of energy release in these sources is via jets.

The Javalambre Photometric Local Survey (J-PLUS) is an ongoing 12-band photometric optical survey, observing thousands of square
degrees of the Northern hemisphere from the dedicated JAST/T80 telescope at the Observatorio Astrofísico de Javalambre.
The larger field of view (FoV), high spatial resolution, contiguous narrow band filters cover a wide wavelength (330-1100 nm)
of J-PLUS/J-PAS surveys act like a low resolution IFU, which is suitable for spatially resolved studies of galaxies. J-surveys have
large Field of view (FoV) and can offer large contiguous observing areas to understand the complete structure of all galaxies
and trace their environment without any pre-selection. In my talk, I will present the results from the spatially resolved study of Halpha 
emission line maps of nearby galaxies at z < 0.017 using JPLUS DR3. We validate our method to build the J-PLUS IFU (J-IFU) emission line maps 
with other IFUs such as CALIFA, MANGA and MUSE. I will also present spatially resolved star-forming regions, its photospectra and star formation maps 
of JPLUS galaxies.

The James Webb Space Telescope has shown us that we cannot consider exoplanet atmospheres as globally uniform objects in chemical equilibrium. On the contrary: day and night sides can have a completely different composition and disequilibrium effects such as mixing and photochemistry will affect chemical abundances, and hence, our understanding of how these planets were formed.

In this talk, I will present new chemical models that incorporate disequilibrium chemistry and three-dimensionality in hot Jupiter atmospheres. I will show that photochemistry can have a global impact and may explain some enigmatic observations on ultra-hot planets. Finally, I will discuss the important effect that photodissociation and ionization have on the atmospheric structure of exoplanets.

The conventional (blink) detection techniques require large aperture telescopes for finding the faintest Solar System objects. Nevertheless, unknown objects can be discovered from stacking short exposures across all potential trajectories. This method is called Synthetic Tracking (ST). Due to the large number of potential trajectories, ST is perceived as computationally expensive, thus most surveys still prefer the blink method.

I will present a moving object detection software called Synthetic Tracking on Umbrella (STU), which leverages GPU computation and multiple search-space optimizations for real time synthetic tracking of fast-moving NEOs, even on large, multi-CCD instruments. This software was validated using a large observational archive and multiple mini-surveys, operating in near real-time under realistic conditions. The archive, of more than 100 000 images, was obtained from various telescopes including the 0.25m T025-BD4SB from Bucharest Observatory, the 1.52 m Telescopio Carlos Sánchez, as well as the 2.54m Isaac Newton Telescope. The most active telescopes used for mini-surveys are the 1.6m KASI telescope located in Chile and the aforementioned INT.

The STU detection rate depends on the quality of the input images. For example, on the TCS frames without pre-processing issues no object was missed. Similarly, an analysis on the WFC dataset has shown an 82% detection rate, with most false negatives again coming from pre-processing issues. From the real-time mini-surveys, key examples are 2023 DZ2, a NEO and former Virtual Impactor, discovered by our group in February 2023, and 2024 CW2, a fast-moving NEA (9.5 arcsec/min), reported by us the same day the data was acquired. Even at this apparent motion, the scanning phase of the synthetic tracking operation finished faster (15 min) than the data acquisition (20 min).

Through our work, we have shown that Synthetic Tracking is not as expensive as was once thought and now it can be done at survey speed. For this reason, we expect that Synthetic Tracking will become a foundational method of asteroid discovery and will thus completely displace the blink method and single-image trail detection approaches.