Wednesday Colloquium


"Light particle dark matter in the forward region of the LHC and in astrophysics"

Sebastian Trojanowski (AstroCent, CAMK , Warsaw)

Light and feebly interacting new physics particles with the mass of order the proton mass or lower have become one of the primary targets in both theoretical and experimental studies in (astro)particle physics in recent years with strong connections to dark matter searches. In my talk, I will overview these efforts and the motivations behind them. I will then describe briefly a new physics program dedicated, i.a., to these searches in the far-forward region of the Large Hadron Collider (LHC). Interestingly, such scenarios can also lead to interesting astrophysical bounds that will be presented.


"Metal-poor massive stars: Linking gravitational waves, star-formation and the dawn of the Universe"

Dorottya Szécsi (Uniwersytet Mikołaja Kopernika, Toruń)

What do gravitational waves have in common with ancient globular clusters? What links these to cosmic explosions like gamma-ray bursts, to the energetic radiation in star-forming galaxies and even to the dawn of our Universe? What they have in common, is that all these phenomena — and more — have been theorized to stem from metal-poor massive stars, in one way or another. In my talk, I will explain these theories, and suggest new perspectives on how to combine them.


"Extreme accretion and ejection in ultraluminous X-ray sources"

Ciro Pinto (INAF, Astronomical Observatory of Palermo)

The detection of fully-grown supermassive black holes in active galactic nuclei at high redshifts, when the Universe was young, challenges the theories of black holes growth, requiring long periods of high accretion, most likely above the Eddington limit. These objects will be difficult to probe even with future advanced observatories. Ultraluminous X-ray sources (ULXs) are nearby neutron stars and, perhaps, stellar-mass black holes accreting above their Eddington limit. This was understood after the discovery of coherent pulsations and cyclotron lines in some ULXs, indicating that at least a fraction of them hosts neutron stars as compact objects and, finally, the discovery of powerful winds that were predicted by theoretical models of super-Eddington accreting compact objects. ULX winds carry a huge amount of power owing to their mildly relativistic speeds (~0.1-0.3c) and may be able to significantly affect the surrounding medium, likely producing the observed 100s pc superbubbles, and limit the amount of matter that can reach the central accretor. The study of ULX winds is therefore quintessential to understand 1) how much and how fast can matter be accreted by compact objects and 2) how strong is their feedback onto the surrounding medium in the regime of high accretion rate such as for quasars and supermassive black holes at their peak of growth. I will provide an overview on this phenomenology and highlight exciting results from some recent observational campaigns.


"What was the last Nobel Prize in Physics given for?"

Szymon Malinowski (Department of Physics, Warsaw University)