Seminars

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

Salle de réunion AGO (local -1/14), Institut d'Astrophysique et de Géophysique
Bâtiment B5c, Quartier Agora, Allée du 6 Août, 19C, B-4000 Liège 1 (Sart-Tilman)

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.

An absence of 60% spin-up companions in wide hot subdwarf binaries
Xiaoyu Ma (STAR Institute Université de Liège)

Le lieu où se tiendra cet évènement n'est pas encore déterminé...

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 40% 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 ～60% of companions, even among relatively bright targets, poses a challenge to the commonly held view that sdO/B formation universally requires binary interaction.

TBD
Maxime Fays (ULiege - STAR - Ograv)

Salle de réunion AGO (local -1/14), Institut d'Astrophysique et de Géophysique
Bâtiment B5c, Quartier Agora, Allée du 6 Août, 19C, B-4000 Liège 1 (Sart-Tilman)

TBD

TBD
Aravind Krishnakumar (STAR Institute Université de Liège)

Salle de réunion AGO (local -1/14), Institut d'Astrophysique et de Géophysique
Bâtiment B5c, Quartier Agora, Allée du 6 Août, 19C, B-4000 Liège 1 (Sart-Tilman)

TBD

TBD
Angelos Nersesian (STAR Institute Université de Liège)

Salle de réunion AGO (local -1/14), Institut d'Astrophysique et de Géophysique
Bâtiment B5c, Quartier Agora, Allée du 6 Août, 19C, B-4000 Liège 1 (Sart-Tilman)

TBD

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

Salle de réunion AGO (local -1/14), Institut d'Astrophysique et de Géophysique
Bâtiment B5c, Quartier Agora, Allée du 6 Août, 19C, B-4000 Liège 1 (Sart-Tilman)

TBD

TBD
Martin Farnir (STAR Institute Université de Liège)

Salle de réunion AGO (local -1/14), Institut d'Astrophysique et de Géophysique
Bâtiment B5c, Quartier Agora, Allée du 6 Août, 19C, B-4000 Liège 1 (Sart-Tilman)

TBD

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

Salle de réunion AGO (local -1/14), Institut d'Astrophysique et de Géophysique
Bâtiment B5c, Quartier Agora, Allée du 6 Août, 19C, B-4000 Liège 1 (Sart-Tilman)

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.