Ema Mlinar: Possible cosmological coupling of black holes
torek, 9. april 2024
Ema Mlinar
(Fakulteta za matematiko in fiziko)
Besides some well-established solutions for black holes, there exist many alternative ones. In the last years, a model of a black hole with a dark energy interior became popular. The mass of these black holes can couple to the cosmological scale factor, which means that the black hole would grow with time. If the model is correct, such black holes would suffice to account for all of the dark energy in the universe. In this talk I focus on observational tests of this hypothesis using supermassive black holes as well as stellar-mass ones. There is a lot of data for masses of supermassive black holes at different redshifts, which enables us to track their evolution with the scale factor. On the other hand, this is not possible for stellar-mass black holes. We can instead use X-ray binaries containing a black hole, where we ultimately use the age and the mass of the black hole to determine the coupling parameter.
Video is available on this link!
Thibault Merle: Spectroscopic binaries and higher-order systems in large surveys
torek, 7. november 2023
Thibault Merle
(Université Libre de Bruxelles, Belgija)
Multiplicity among field and cluster stars is ubiquitous. The properties of binary stars are therefore fundamental to understand how stars were formed and how they evolve. Interaction processes between components may lead to complex outcomes like chemically peculiar stars, stripped stars, transients and merger events. Binaries are easily identified through radial velocity variations measured in spectroscopy. Large spectroscopic surveys, like the Gaia-ESO survey (GES), are providing high accuracy radial velocities and chemical abundances for hundreds of thousands of stars. Among them, spectroscopic multiple stellar systems (spectroscopic binaries with one ore more visible components: SBn, with n≥1) deserve special investigation since the determined radial velocities and chemical abundances could be potentially affected by multiplicity. In this talk, I will summarize the findings obtained in the GES in terms of stellar multiplicity and the statistical properties of binary stars and present perspective in the context of other surveys (GALAH, 4MOST, MSE).
Video is available on this link!
Blaž Bortolato: Learning the Composition of Ultra High Energy Cosmic Rays
torek, 24. oktober 2023
Blaž Bortolato
(Institute Jožef Stefan, Ljubljana)
Earth is continuously exposed to a flux of cosmic particles, some of which carry very large energies, of the order of $10^{18}$ eV – $10^{20}$ eV. The origin and composition of these ultra-high energy cosmic rays (UHECRs) are still open problems.
In this talk, I will present a novel method for inferring the mass composition of UHECRs from the electromagnetic profile of their air showers. Furthermore, I will explore opportunities for enhancing the statistical significance of this dataset by exploiting its correlation with other shower observables.
Video is published on this link!
ASA AZ800 – nov teleskop na Astronomskem observatoriju na Golovcu
sreda, 11. oktober 2023
Dominik Patrick Kagerer
commisioning engineer
ASA Astrosysteme GmbH, Avstrija
Nov teleskop AZ800 s premerom glavnega zrcala 80 cm, ki smo ga prejeli ta teden, nam bo predstavil inženir podjetja ASA, ki je tudi vodil njegovo postavitev ter kalibracijo. Debata bo precej tehnične narave vendar nedvomno zanimiva, saj bomo bolj podrobno spoznali zmogljivosti in možnosti uporabe novega teleskopa, ki je tako postal naslednik teleskopa Vega v veliki kupoli observatorija.
Video is published on this link!