Retrieval and seasonal variations of aerosols in the Martian atmosphere from the NOMAD instrument on board the Trace Gas orbiter
Zachary Flimon (LPAP/STAR/ULiège)

Mars is a terrestrial planet with a mass and a much thinner atmosphere compared to Earth. Although its rotation period is similar to Earth’s day, its revolution around the Sun takes nearly twice as long. The planet’s elliptical orbit results in strong seasonal variations in its atmosphere. Martian aerosols composed of dust, H2O ice, and CO2 ice clouds are strongly influenced by these seasonal cycles. This work focuses on retrieving the optical properties of aerosols, specifically extinction and particle size, using solar occultation measurements from the Nadir and Occultation for Mars Discovery (NOMAD) instrument aboard the ExoMars Trace Gas Orbiter (2016–present). NOMAD consists of three channels: UVIS (Ultraviolet–Visible, 200–650 nm), SO (Solar Occultation, 2.3-4.3 μm), and LNO (Limb Nadir and Occultation, 2.2-3.8μm). In solar occultation, we can probe the vertical structure of the atmosphere and derive vertical opacity profiles. In the first part of this work, we use the UVIS channel alone to study aerosol optical properties. Although UVIS cannot determine aerosol composition, its large number of spectral points and low noise level make it well suited for retrieving sub-micron particles. We then studied aerosols using the SO channel, which allows us to retrieve aerosol composition as well as larger particle sizes at lower altitudes. Finally, to take advantage of the simultaneous measurements from both channels, we merged the spectra from UVIS and SO and retrieve aerosol properties jointly. This combined approach improves vertical coverage and provides both size and composition information in a single, consistent retrieval. Using the combined UVIS and SO dataset, we produced a global climatology spanning mid–Martian Year (MY) 34 to MY 37. This climatology captures the seasonal evolution of aerosols, including dust storm activity and H2O ice distributions during all Martian seasons. Our results are consistent with previous datasets and reveal that dust and H2O ice can coexist at specific altitudes, providing new insights into their coupled behavior in the Martian atmosphere.

From Small Worlds to Giant Planets: Uncovering New Exoplanets with Ground-Based Observations
Mathilde Timmermans (University of Birmingham)

Discerning patterns and trends in the physical properties of exoplanets is now possible thanks to the growing number of planet discoveries. In particular, TESS has been instrumental in adding to the sample with the detection of over 7800 potential planets, of which more than 750 have been confirmed in the last 8 years. The distinct subpopulations that have emerged from grouping planets in different parameter spaces are now being tested against formation and evolution theories. Linking the two is still proving challenging in some cases, highlighting the need either to revise the current theories or increase the size of the statistical sample for the rarer planets.

In this talk, I will discuss the efforts to validate planet candidates with the SPECULOOS and ASTEP ground-based facilities, focusing on small and giant planets orbiting M dwarfs. I will highlight the key advantages of these facilities and present ongoing projects. Particularly, I will discuss the latest discoveries of the MANGOS programme which I am currently leading.

The Solar Modelling Problem
Gaël Buldgen (STAR Institute Université de Liège)

The revision of the solar abundances in the early 2000’s has proven to be a thorny issue that is still causing trouble to solar modelers 20 years later. Subsequent re-analyses in 2009, 2011, 2021 and 2022 (Asplund et al. 2009, Caffau et al. 2011, Asplund et al. 2021 and Magg et al. 2022) have provided contradicting result, leading to a lasting debate between “high-metallicity” and “low-metallicity” solar models. In this talk, I will discuss the more general aspects of the so-called “solar modelling problem” and how it cannot be reduced to a simple problem of chemical abundances but rather a more fundamental issue linked with our current modelling capabilities of the solar interior.

Absence of Spin‑Up Companions in Half of Wide Hot Subdwarf Binaries
Xiaoyu Ma (STAR Institute Université de Liège)

Binary stars play critical roles across a wide range of astrophysical contexts, including the formation of exotic stellar objects and planetary systems, the progenitors of supernovae, and the sources of gravitational waves. They are widely believed—both from theoretical models and, more recently, from observational evidence—to be a primary channel for the formation of hot subdwarfs (sdO/B stars). Here we report an unexpected result that only about half of companions in a golden sample of wide hot subdwarf binaries exhibit measurable rotational signals attributable to magnetic modulation, based on a comprehensive survey of nearly 5000 TESS and Kepler sdO/B targets. Their rotation periods are predominantly shorter than 5 days, a distribution strikingly different from that of single field MS stars, whose rotation periods peak around 20 days. This markedly faster rotation suggests that the old MS companions in wide sdO/B binaries must have undergone a spin-up process through past mass accretion, as their rotation rates are comparable to those of much younger MS stars in open clusters. However, the absence of any detectable rotational signal in the remaining near half of companions, even among relatively bright targets, poses a challenge to the commonly held view that sdO/B formation universally requires binary interaction.

The AI Revolution in Academia: A Practical & Honest Guide for Researchers and Teachers
Maxime Fays (ULiege - STAR - Ograv)

Ready or not, Generative AI is reshaping how research is done and how students learn. This talk cuts through the noise with practical techniques and honest assessments of both the potential and the pitfalls: what these tools actually are, where they reliably fail, and how to direct them effectively whether for writing grants, designing exams, or reclaiming time spent on tasks AI handles in seconds.

TBD
Aravind Krishnakumar (STAR Institute Université de Liège)

TBD

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Angelos Nersesian (STAR Institute Université de Liège)

TBD

Genesis: the ESA mission to measure Earth down to the millimeter
Gilles Wautelet (LPAP, STAR Institute, ULiège)

TBD

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Martin Farnir (STAR Institute Université de Liège)

TBD

Orion’s Massive Stars: Delta and Epsilon Ori
Alžběta Oplištilová (STAR Institute Université de Liège)

Massive stars are cosmic engines. By exploding as supernovae, they power galaxies, shape the interstellar medium, and enrich it with heavy elements. Yet, their inner workings remain among the most challenging frontiers in stellar astrophysics. The evolution of massive stars is critically influenced by multiplicity; most have one or more companions, while a few remain single. This raises the question: could these single stars be the end products of multiple systems? Interferometry is one of the best methods for detecting and characterising stellar multiplicity. The Orion complex is the nearest massive-star-forming region with multiple OB stars, and thus the most suitable for detailed studies. It hosts a number of massive stars, particularly in the Orion Belt. I constructed two complex models: the triple star Delta Ori and the single star Epsilon Ori using interferometric data in synergy with astrometry, photometry, high-resolution spectroscopy, and spectral energy distribution. Delta Ori is currently in the pre-mass-transfer evolutionary stage, while Epsilon Ori is a significantly oblate supergiant due to its rapid rotation. As the only massive single star in the Orion Belt, Epsilon Ori likely follows a non-standard evolutionary path.