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.

Comet C/2020 F3 (NEOWISE): From naked eye spectacle to scientific insights
Aravind Krishnakumar (STAR Institute Université de Liège)

Comets are among the most primitive bodies in the Solar System, preserving a record of the physical and chemical conditions prevalent during their formation. The study of cometary comae through photometry and spectroscopy provides critical insights into volatile composition and outgassing processes. In particular, production rates of commonly observed species such as OH, NH, CN, C₂, and C₃ serve as key diagnostics of the nucleus composition and its evolutionary state. The abundance of molecular nitrogen relative to CO and H₂O, however, remains poorly constrained. In the optical regime, these parent volatiles can be probed only indirectly through their ionic emissions, making their detection both essential and challenging due to their extremely low densities. The Great Comet of 2020, C/2020 F3 (NEOWISE), has been extensively studied using very high-resolution spectroscopy; however, ionic emissions have not been previously reported. In contrast, long-slit low-resolution spectroscopy of such a bright comet enables detailed investigation of spatial emission profiles, offering a complementary and powerful diagnostic. In this seminar, I will take you through the realm of cometary science and present the detection of ionic emissions, including N₂⁺, CO⁺, and H₂O⁺ in C/2020 F3 (NEOWISE), along with other unusual spectral features. I will discuss the derived relative abundances and their implications for cometary formation conditions and volatile chemistry, alongside an overview of production rates of key neutral species. Additionally, I will highlight the detection of a particularly intriguing optical emission and explore its potential significance.

Characterizing the physical properties of strong lenses and local galaxies with Euclid
Angelos Nersesian (STAR Institute Université de Liège)

In this talk, I will present my work on the local Universe in the context of the Euclid mission, with a focus on its applications to the nearby strong-lens system NGC 6505. I will then introduce preliminary results from a sample of strong gravitational lenses, including measurements of redshifts, stellar masses, Einstein radii, and galaxy sizes. Finally, I will discuss what this statistically significant sample can reveal about the properties of strong-lens populations and their role in galaxy evolution.

Mars aurora: discovery, imaging and relation to solar wind
Jean-Claude Gérard (LPAP, STAR, ULiège)

Auroral emissions on the Mars nightside were initially observed as individual events of MUV emission by the SPICAM spectrometer on board Mars Express in 2005. These observations have shown the auroral ultraviolet emissions are highly correlated with crustal magnetic fields structures. MAVEN's Imaging Ultraviolet Spectrograph (IUVS) has measured hundreds of individual discrete MUV electron auroral events since 2014 and showed that they can also occur globally, in regions of weak or absent crustal fields. Another type of event is the ‘’diffuse’’ aurora which occurs following Solar Energetic Particle (SEP) events and covers a large fraction of the planet. It is caused by the interaction of very energetic electrons and protons with the atmosphere. Since April 2021, the EMUS EUV/FUV spectrograph on board the Emirates Mars Mission (EMM) has shown that the FUV electron auroral emission is not necessarily "discrete" but is observed in a variety of morphologies. Crustal field aurora and enigmatic "sinuous" aurora have well-defined edges, while most emission away from strong crustal fields is fainter and "patchy". Finally, on the dayside, enhancements of Lyman-a have also been observed, resulting from the interaction of solar wind protons with the hydrogen corona surrounding the planet. We will show that visible counterparts to the UV emissions would probably be detectable and visible to future Mars astronauts. This seminar will also describe the current state of Mars aurora modelling and future investigations.

Seismology of solar-like stars along their evolution
Martin Farnir (STAR Institute Université de Liège)

The advent of space-borne missions lead to the acquisition of extremely precise data. This allowed us to unveil the secrets harboured by stars with unmatched accuracy. This was thanks to asteroseismology, the science of stellar oscillations and their relation with the stellar structure. In this talk, I will present tools I develop to take full advantage of the information held by stellar oscillations of solar-like stars - i.e. stars with masses similar to our Sun - along their evolution, from the main sequence all the way to the red-giant phase. These are WhoSGlAd, for the study of acoustic glitches - sharp feature in the stellar structure leaving a signature in the oscillation spectrum - EGGMiMoSA, suited to the study of the complex mixed-modes - modes displaying both a pressure and gravity nature - pattern displayed by subgiant and red-giant stars, and PORTE-CLES, a minimisation tool for the search of optimal stellar models, representative of a set of observables.

Galaxy Evolution in the Fornax Cluster
Marc Sarzi (Armagh Observatory and Planetarium)

Galactic environment is thought to be one of the key factors in driving the cosmic quenching of star formation in galaxies. The Fornax cluster is a nearby intermediate-mass cluster that is more representative of the clusters found in the Universe compared to other nearby clusters such as Virgo and Coma. Fornax thus represents an ideal environment to understand the relative role of hydrodynamic and gravitational processes affecting galaxies in crowded environment.

In this context, I will discuss the results of the Fornax3D magnitude-limited survey of galaxies in the Fornax cluster with MUSE integral-field spectral. Additionally, I will present the results of ancillary studies based on deep optical and radio observations (with VST and MeerKAT) revealing objects currently on-going star-formation quenching. To further gain insight on the physical mechanisms behind such phenomena, we derive the star-formation history of Fornax galaxies with a spectrophotometric approach to both MUSE integral-field spectroscopic and S-PLUS imagining data. At the same time we also explore Fornax-like clusters in the TNG-50 simulations to derive the neutral-gas predicted distribution both across the whole cluster and around individual galaxies, following this also in time. This gives us a view of both on-going gravitational and hydrodynamical interactions in the Fornax cluster galaxies as well as a gauge on the past impact that these had in driving their star-formation histories, which we can compare to model predictions.

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.

Asteroseismology with Earth 2.0: Probing Stellar Rotation and Magnetism
Gang Li (University of Southern Queensland)

The Earth 2.0 (ET) mission is a planned space-based telescope at the Sun–Earth L2 point, comprising six co-pointed 28-cm transit telescopes that will monitor a 550-deg² field encompassing the original Kepler field and its surroundings for four years, together with a 35-cm microlensing telescope directed toward the Galactic bulge. Its long-baseline, high-precision photometry will create new opportunities for asteroseismology across different stellar masses and evolutionary stages.

I will review recent progress in probing stellar rotation and magnetism, from main-sequence pulsators to red giants. Gravity-mode period spacings, rotational splittings, and mixed modes have revealed internal rotation profiles that are not in good agreement with current theories, posing a major challenge to our understanding of angular-momentum transport. Meanwhile, frequency asymmetries and magnetic perturbations to gravity and mixed modes are beginning to reveal kilogauss internal magnetic fields in both main-sequence stars and red giants.

Finally, I will present the current ET field of view, seismic target selection, and observing strategy. The 15-min full-frame cadence will provide long and nearly continuous light curves for large samples of pulsating stars, while high-frequency oscillations require additional high-cadence observations. With a seismic sample expected to be much larger than Kepler’s, ET will extend studies of stellar rotation and magnetism from individual benchmark stars to stellar populations.

Internal rotation and magnetic fields of the intermediate-mass main-sequence star KIC 9244992
Masao Takata (The University of Tokyo, Tokyo (Todai))

Asteroseismology is the study of the structure and dynamics of stars based on their surface oscillations.  This field has advanced considerably in recent years due to the high-precision photometry provided by space missions such as CoRoT, Kepler and TESS, and this progress is set to continue with the upcoming PLATO mission.  This presentation focuses on the F-type main-sequence star KIC 9244992, which was observed by the Kepler space telescope for almost four years.  It is a pulsating variable star of the delta Sct and gamma Dor hybrid type, meaning its oscillation periods fall into two regimes: a few hours for acoustic modes and approximately one day for gravity modes.  The most notable aspect is the clean rotational multiplets evident in the Fourier spectrum of the light curve.  I will first summarise the results of its internal rotation and then introduce a recent result concerning its internal magnetic fields.

Galactic chemical evolution in 3D NLTE
Nick Storm (MPIA, Heidelberg)

In this talk, I will present recent advances in our understanding of the history of Galactic nucleosynthesis, driven by new observational data and improved stellar modelling. A key focus will be on insights into stellar chemical abundances made possible by state-of-the-art 3D radiation-hydrodynamics stellar atmospheres and non-local thermodynamic equilibrium (NLTE) spectral models. These results are part of the multidisciplinary series of studies Observational Constraints on the Origins of the Elements, which aims to provide a comprehensive framework for tracing the Galactic evolution of elemental abundances—from the lightest species (C and O), through the α-elements and Fe-peak elements, to the products of s- and r-process nucleosynthesis. I will present our 3D NLTE findings on the evolution of Fe-peak elements and discuss their significance for understanding core-collapse supernovae (CCSNe), Type Ia supernovae, and their progenitors. I will then explore neutron-capture element abundance ratios in the context of asymptotic giant branch (AGB) stars and neutron star mergers. The talk will conclude with a forward-looking perspective on extragalactic nucleosynthesis, emphasising the opportunities enabled by next-generation facilities such as JWST and the ELT.

Active galaxies and supermassive black holes.
Professor Dhruba Saikia (National Centre for Radio Astrophysics (NCRA) of the Tata Institute of Fundamental Research (TIFR))

Galaxies, which are the fundamental building blocks of the Universe, are often much more than the billions of stars and the medium between them, which are all embedded in massive dark matter halos. They harbour supermassive blackholes in their nuclear regions with masses ranging from millions to billions of solar masses. These active galactic nuclei are responsible for some of the most energetic phenomena in the Universe with luminosities up to a hundred trillion times that of our Sun. They can eject jets of relativistic plasma over millions of light years, spanning a distance of up to about 200 times the size of our own Galaxy, the Milky Way, at nearly the velocity of light. In this talk, I will introduce you to this fascinating world of active galaxies, our current understanding of these objects and highlight a couple of new interesting results.

The effect of stellar surface granulation on spectral line variability
Cis Lagae (University of Warwick, UK)

Radial velocity noise from the exoplanet hosting star, originating from stellar activity such as faculae and granulation, hampers the detection and characterization of earth-mass exoplanets. A profound understanding of how spectral lines behave in the presence of these stellar components is necessary to eliminate such radial velocity noise from observations. In this context, we have built a framework that isolates and characterizes the radial velocity signature due to granulation for individual, synthetic, spectral lines computed from 3D stellar models. Building on this, we expanded the method to larger spectral regions, including tens of spectral lines, with the goal of mimicking real disk-integrated stellar observations. Using this method, we have quantified how granulation affects the properties and radial velocities of spectral lines differentially, from disk center to the stellar limb. We found that certain groups of lines behave radically differently than others, based on their atomic parameters and line depth. In addition, we investigated how different methods of computing radial velocities affect these relationships. Ultimately, this work will enable us to identify key granulation noise diagnostics across the optical spectrum that can be used to reduce the granulation-induced radial velocity noise from observations.

TBD
Quihan He (Durham University or Heidelberg)

TBD
Martin Makler (TBD)

TBD

From Quiescence to Glow: Unveiling the Pre-Perihelion Activity of Interstellar Comet 3I/ATLAS through Multi-Epoch Spectroscopy
Rohan Rahatgaonkar (Pontificia Universidad Católica de Chile)

The discovery of 3I/ATLAS (C/2025 N1) in July 2025 marked the detection of the third confirmed interstellar object passing through our Solar System, and the first ISO discovered several months before perihelion. With an extreme hyperbolic orbit (e ≈ 6.14) and an estimated age older than the Solar System, 3I/ATLAS provides a unique window into the chemistry and conditions of ancient extrasolar planetary systems. We present spectroscopic observations from SOAR and VLT facilities tracking 3I from 4.4 to 2.85 AU, revealing its evolution from quiescence to activity. Our data show a red continuum spectrum with complex organics, the dramatic onset of CN emission at 3.65 AU, and remarkably, strong Ni I emission beginning at 3.78 AU with no detectable Fe I. The unusually steep heliocentric scaling of production rates (Q(Ni) ∝ r_h^(-7.7) and Q(CN) ∝ r_h^(-6.7)) suggests low-activation-energy release mechanisms inconsistent with simple volatile sublimation, potentially involving metal carbonyls or metalated organics. I will discuss these findings in the context of 3I's ancient origins and our campaigns to monitor its evolution through pre-perihelion. 

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

Genesis is an ESA space geodetic mission that will be launched in early 2029. It aims at improving and homogenizing the International Terrestrial Reference Frame (ITRF), with a target accuracy for station position and velocity of 1mm and 0.1mm/year, respectively. In order to achieve this high-accuracy level, Genesis will collocate, for the first time ever, the four space geodetic techniques on a single platform: the spacecraft will host a Global Navigation Satellite Systems (GNSS) receiver, a Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) receiver, a Satellite Laser Ranging (SLR) retroreflector and a Very Long Baseline Interferometry (VLBI) transmitter. Because these instruments use radio signals (except SLR) that travel into the Earth’s ionosphere and plasmasphere, the contribution of these ionized layers of the atmosphere must be accurately modeled and mitigated to ensure precise and reliable measurements that will be used to compute the ITRF. After the presentation of the Genesis mission and the related geodetic framework, we investigate the magnitude and the variability of the ionospheric contribution on the future Genesis observables. Then, based on simulations of GNSS satellite visibility from Genesis, we explore the possibility to take benefit from Genesis GNSS observations to remotely sense the ionosphere and the plasmasphere using the radio-occultation technique.