Vorträge, Seminare, Ereignisse

Abstract
Binary interactions shape the evolution of the most massive stars, leading to significant deviations from the evolutionary pathways possible in single star evolution. These processes impact the universe at large scales and result in high energy events such as peculiar supernovae and gravitational wave sources. To understand these outcomes, it is important to assess binary evolution in early stages ranging from pre-interaction, roche-lobe overflow and post-interaction phases. I will discuss the current progress in our understanding of mass-transferring binaries, covering the impact of this process on the donor star (with the possible production of a stripped star), as well as the response of its companion. Of particular importance in recent years is the identification of bloated stripped stars caught immediately after interaction which provides a snapshot of the end-states of mass transfer, and I will discuss how their properties constrain orbital evolution and the efficiency of mass transfer. I will also emphasize that many of the uncertain processes in massive binary star evolution can also be assessed through the study of intermediate mass systems, for which the physics in early evolutionary phases does not differ significantly. To arrange a visit with the speaker during the visit, please contact their host: Jaime Villaseñor (MPIA)

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Giant low surface brightness galaxies (gLSBGs) have the largest discs in the Universe with the radii up to 130 kpc. The formation of such enormous discs is a stress-test for the hierarchical galaxy formation paradigm and without clarifying it we cannot paint a coherent picture of galaxy evolution. In the talk I will give the answers to the following questions. How rare are gLSBGs? What are the formation scenarios of gLSBGs? And how does it all correspond to the results of modern cosmological simulations? These answers are based on both in-depth study of 8 gLSBGs, including the results of our deep spectroscopic and photometric observations, HI data collected in the framework of our observing programs and complemented by archival datasets. Finally, we used deep optical images from HSC Subaru Strategic Program and publicly available redshift catalogs, estimated the volume density of gLSBGs in the local Universe and compared it to state-of- the-art numerical simulations.

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To arrange a visit with the speaker during the visit, please contact their host: Dominika Wylezalek

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DRAGON star cluster simulations have provided the first fully realistic long-term simulations of globular star clusters, have reproduced LIGO/Virgo observed binary black hole mergers, and are now entering into the next phase to simulate more massive, young and nuclear star clusters. They are based on the direct N-body simulation code Nbody6++GPU. In the talk an introduction and overview to direct N-body simulation and DRAGON simulations is given. Two current new applications are then shown, first initially very dense star clusters which form quickly an intermediate mass black hole of order 50.000 solar masses, which could be a seed for massive black holes in the early universe. Second, a still ongoing project is discussed, in which an already pre-existing supermassive black hole in a nuclear star cluster is followed, how it tidally disrupts stars, and captures low-mass stars, white dwarfs, neutron stars and stellar mass black holes.

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By precisely measuring the motions of stars on the sky over time, the Gaia mission is conducting a comprehensive census of the Milky Way's binary stars. These data are transformative both for population modeling and for discovery of rare objects. I will describe our emerging view of the populations of black holes, neutron stars, and white dwarfs in au-scale binaries, focusing in particular on their mass, period, and eccentricity distributions. Compared to previous surveys, Gaia is revealing post-interaction binaries in wider orbits, whose properties are difficult to explain with standard binary evolution models. I will discuss how the Gaia catalogs can be leveraged for statistical inference, despite their complex selection function, and how they can discriminate between competing formation models.

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KoCo Signature Speaker (GC)