Events, Seminars, Talks

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I will present the most recent developments and science cases from our newly established research group on computational astrophysics at the University of Duisburg-Essen. The bouquet contains the formation of circumplanetary disks, the tidal disruption of disk fragments, the launching and acceleration of protostellar jets, diverse stellar feedback effects, and the trapping of compact HII regions. If time allows, I would like to also present the status of currently ongoing studies such as the atmospheric signatures of magma worlds, the accretion flows from disks to stellar surfaces and the (in)stability of star-forming filaments.

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Recent JWST and ALMA observations have revealed that a substantial fraction of galaxies at very high redshift are rotationally supported disks. Many of these systems host kinematically cold, or “settled,” gaseous disks, a finding that stands in tension with the expectations of many galaxy-formation models. In this seminar, I will present an overview of cosmological simulations of disk-galaxy formation. I will discuss the properties of gas-rich, high-redshift disks, their turbulent nature, and how these early phases of disk assembly connect to spectroscopic and astrometric observations of the Milky Way. Finally, I will show new results indicating that turbulent, early-Universe galaxies are more susceptible to global gravitational instabilities, such as bar formation, than previously thought. These results carry important implications for the rapid buildup of galactic bulges and the fueling of central black holes. To arrange a visit with the speaker during the visit, please contact their host: Eva Schinnerer

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Active galactic nuclei are mostly powered by inflow through accretion disks onto central supermassive black holes. Beyond a few times their Schwarzschild radius, gravitational instability in these disks leads to self-regulated formation and evolution of massive stars which chemically enrich their neighborhood along with stellar-mass black holes. These compact remnants are captured by coexisting massive main sequence stars, form close binaries, readily merge, and excite intense gravitational waves with potentially observable electromagnetic signatures. The massive stars' migration, with or without black hole cores, efficiently transporting mass regardless of the Eddington limit and promoting the rapid growth of supermassive black holes in the early Universe. Analogous physical processes are also relevant in the context of planet formation in protostellar disks. They account for the persistent super-solar metallicity, especially in Nitrogen and iron, inferred from broad emission lines of high and low redshift AGNs. To arrange a visit with the speaker during the visit, please contact their host: Haochang Jiang

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Modern astronomy has entered a regime in which the central challenge is no longer data acquisition, but data integration. Billions of stars are now observed across (phase-)space, frequency, and time, yet each modality captures only a partial view of the processes that shape our Galaxy. The next frontier in Galactic archaeology lies in unifying these dimensions into a coherent framework. In this talk, I will present new data-science methods that integrate spectroscopy, asteroseismology, and astrometry to infer precise stellar ages, chemical abundances, and dynamical histories across the Milky Way. I will particularly highlight scalable time-domain techniques for extracting stellar oscillations from large survey data, transforming time-series observations into powerful constraints on Galactic evolution. These approaches quantify the efficiency with which disk stars lose dynamical memory, and show that the disk’s chemical bimodality likely reflects a merger-driven origin linked to the formation of the Galactic bar. I will conclude by outlining a path toward constructing a unified, multi-dimensional map of the Milky Way, spanning spatial, chemical, dynamical, and temporal dimensions, using datasets such as Euclid and Rubin LSST, positioning time-domain and multi-modal data science at the centre of Galactic evolution studies.

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Ultra-hot Jupiters (UHJs) have become prime targets for atmospheric characterisation. Owing to their close-in orbits and the early spectral types of their host stars, these planets are unique laboratories for studying atmospheric physics and chemistry under extreme conditions. One of the most compelling processes to investigate in these environments is atmospheric escape, which is thought to be a major driver of the long-term evolution of planetary atmospheres across a wide range of planets. Atmospheric mass loss is powered by heating processes that are strongly influenced by non-local thermodynamic equilibrium (NLTE) effects. I will show how NLTE processes shape the physical and chemical structure of UHJ atmospheres and discuss the observational evidence supporting these results on the basis of multiple datasets. To arrange a visit with the speaker during the visit, please contact their host: Maria Bergemann

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A third of all massive stars are predicted to lose their hydrogen-rich envelope through mass transfer or common envelope ejection initiated by a binary companion star. As a result, the hot and compact helium core is exposed. These "stripped stars" are the direct progenitors of hydrogen-poor supernovae and merging binary neutron stars, but they are also so hot that they should boost the ionizing output from bursty star-forming galaxies. Despite their importance, stripped stars remained, until recently, observationally unconfirmed since their predicted existence over half a century ago. We found the first set of stripped stars by combining ultraviolet and optical photometry with follow-up spectroscopy in the Magellanic Clouds. By fitting their spectra with a new grid of models, we could measure stellar properties and thus confirm that the predictions from binary evolution models are broadly consistent with observed stripped stars. To arrange a visit with the speaker during the visit, please contact their host: Jaime Villasenor

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