Events, Seminars, Talks

Abstract
The expansive, interdisciplinary nature of astronomy, combined with its open-access culture, makes it an ideal testing ground for exploring how Large Language Models (LLMs) can accelerate scientific discovery. Recent developments in LLM reasoning capabilities have shown substantial progress — our work demonstrates that AI agents can now achieve gold medal performance on International Olympiad on Astronomy and Astrophysics (IOAA) problems, indicating their growing analytical abilities. In this talk, I will present our recent advances in applying LLMs as agents to real-world astronomical challenges. We demonstrate how LLM agents can conduct end-to-end research tasks in galaxy spectral fitting — encompassing data analysis, strategy refinement, and knowledge accumulation — approaching capabilities similar to human intuition and domain knowledge, and extending to spectroscopic measurements that once took months of expert effort and to sifting hundreds of millions of light curves for rare systems. However, limitations remain. The Moravec paradox manifests clearly in astronomy: tasks requiring abstract reasoning may be easier for AI than seemingly simple perceptual tasks, and current models still struggle with chart reading, multi-modal data interpretation, and other fundamental astronomical workflows. To make large-scale applications viable, we developed lightweight, open-source specialized models (AstroSage) that match frontier models on astronomy Q&A at a fraction of the cost, evaluated against carefully curated astronomical benchmarks. Looking ahead, the path forward involves not just better models but a comprehensive ecosystem — rigorous benchmarks, literature-scale retrieval, and agent-ready tools. I will close by reflecting on what this transformation means for scientific understanding itself, and why understanding the universe remains a distinctly human project, even with non-human collaborators. To arrange a visit with the speaker during the visit, please contact their host: Hans-Walter Rix

Abstract
I will review the recent progress that we have made in understanding nucleosynthesis in the Universe and the accretion history of the Milky Way through chemodynamical analysis of the stellar halo. Over the last five years, we have been complementing the discoveries from the Gaia mission with high-resolution spectroscopic follow-ups of halo stars. These studies have provided detailed chemical abundances of stars in stellar streams, revealing the origins of these streams. There have also been serendipitous discoveries during these follow-ups leading to new insights into broader topics in astrophysics, such as the discovery of Li-rich stars in stellar streams and the association of a 33 Msun solar mass black hole with a stellar stream. After reviewing these discoveries, I will discuss the future prospects of this field in light of the recently started spectroscopic surveys, namely 4MOST and WEAVE, hopefully with initial results from them by the time of the colloquium. Finally, I will briefly introduce the next generation spectroscopic facilities that are currently being discussed. In addition to these scientific topics, I will also share my personal experience of being a Gliese fellow at ARI for three years and how it has impacted my career.

Abstract
TBD

Abstract
The first macroscopic interstellar object (ISO) passing through our Solar System, `Oumuamua, was discovered in 2017 and caused a lot of excitement, due to both its novelty and its unexpected properties. The subsequent two discoveries, 2I/Borisov and 3I/ATLAS, appear more like comets. 3I/ATLAS has been observable for most of the last year, and as the first ISO seen in the JWST era has been well studied, and appears to be an ancient object that is significantly older than our Solar System. I will discuss what we have learned about the ISOs seen so far, what the prospects are for this field in the era of Rubin/LSST, and how we could potentially send a spacecraft to see a future visitor up close. To arrange a visit with the speaker during the visit, please contact their host: Markus Hundertmark

Abstract
Westerlund 1 (Wd 1) is the most massive young stellar cluster in the Galaxy, and hosts a uniquely numerous, diverse and nearby population of evolved massive stars including 24 Wolf-Rayet stars, several yellow and red supergiants, a luminous blue variable and over 100 OB supergiants. In this talk I will report on the supergiant B[e] star Wd1-9, which we now know to be a recently stripped massive binary system deeply embedded in a dense rotating circumstellar medium and bipolar photoevaporating outflow reminiscent of a protoplanetary disk wind. I will also detail how hydrodynamic simulations of outflows from massive stars coupled with EWOCS data can constrain supergiant evolutionary pathways in clusters. I will show how a recent (~10 kyr ago) non-conservative mass transfer event can explain the unusual nebulosity around the WR+O binary system Wd1-72. I will also demonstrate how the mysterious "pillar/rat" nebula in Wd 1 could have been produced by the yellow supergiant Wd1-4 transitioning from a red supergiant in the past ~15 kyr, and how similar models of cool supergiants in clusters have the potential to robustly measure their uncertain mass-loss rates.

Abstract
TBD

Abstract
The most distant luminous quasars, now found up to redshifts z~7.5, are in many ways the most robust tools used by astronomers to study the first billion years of our Universe. On the gigaparsec scales of the cosmic web, the Lyman-alpha forest in front of the first quasars gives us the most precise measurement of reionisation's end at z=5.3. Soon, advances in ground-based instrumentation will also yield an accurate value for the process' mid-point, a crucial boundary condition on Cosmic Dawn. On galactic scales, quasar spectra capture metal absorbers from the circum-galactic medium of faint early galaxies which cannot be detected in emission. Using this approach, I will present recent record-breaking observations of the most metal-poor galaxy detected to date: 11,000 times more metal-poor than the Sun, it is the first "ultra" metal-poor galaxy, and gives a fascinating glimpse of the properties of the first metal-poor stars. Finally, the existence of quasars at z>7 is a tremendous mystery in itself: the supermassive black holes powering them cannot easily grow from the remnants of the first stars. I will present cutting-edge observations from JWST which help elucidate this mystery.

Abstract
Hot, massive stars are astrophysical keystones which shape their environment via mechanical and radiative feedback and chemically enrich their cosmic neighborhood since the first generation of (very) massive stars. However, turning this general textbook picture into quantitative prediction remains an ongoing challenge. Recent discoveries, such the surprisingly high metallicity and early nitrogen enrichment in high-redshift galaxies discovered by JWST, put current descriptions and modelling approaches into question, illustrating that the complex puzzle of massive stars and their interplay is everything but complete. To get a robust, quantitative understanding, decoding and predicting the light of hot massive stars marks an astrophysical key technique. Revolving around via the development and application of expanding stellar atmosphere models for hot stars, I will present a selection of recent research results from my group. A particular focus will be on star with strong stellar winds, their enigmatic cosmic role, and the challenge to get a coherent structural and evolutionary understanding of these objects. Moreover, I will present our recent discovery of an unexpected direct transition in the Wolf-Rayet regime from WN to WO subtype occuring at subsolar metallicity as well as ongoing and forthcoming efforts in further developing atmosphere modelling and quantitative spectroscopy.

Abstract
TBA

Abstract
Our unique perspective from within the Milky Way gives us the ability to take images and spectra of individual stars throughout most of the Galaxy. By analyzing this data we have attained a detailed understanding of our Galaxy's stellar populations, gas and dust content, internal dynamics, and star formation, chemical enrichment, and assembly histories. Unfortunately, this level of detail is somewhat unattainable in external galaxies due to stellar crowding, so we must get creative with our analysis methods to account for this. I will present results from two projects. The first involves fitting panchromatic SEDs of resolved stars in two nearby galaxies that have archival observations from HST and JWST, which combine to create the highest resolution broad wavelength coverage possible. This provides an incredible opportunity to study dusty star forming galaxies in high resolution, unveiling why these galaxies are so UV bright for their dust content, and how they form stars despite their low molecular gas mass. The second project involves full-spectrum-fitting of Local Group star clusters from the APOGEE survey. From these high-resolution, integrated-light spectra we can measure the clusters' kinematics, metallicities, and α abundances, which trace the chemical enrichment and assembly history of the galaxy. These two approaches can constrain the assembly and chemical enrichment history of nearby galaxies while providing insight into the fundamental physics governing galaxy evolution in the nearby universe.

Abstract
TBD