Wednesday Colloquium


"Particle acceleration in relativistic magnetospheres"

Benoît Cerutti (Université Grenoble Alpes)

Rapidly rotating neutrons stars and black holes are the central engines of some of the most extreme astrophysical phenomena such as gamma-ray bursts, pulsars, X-ray binaries, binary mergers or active galactic nuclei. The activity of these compact objects is often associated with the creation and the launching of a relativistic magnetized plasmas accompanied by efficient particle acceleration and non-thermal radiation, but the underlying physical mechanisms are still poorly understood. The particle-in-cell method is well-suited to model these processes from first principles. Recent numerical simulations have clearly established that relativistic magnetic reconnection within the magnetosphere of pulsars and black holes plays a crucial role in dissipating magnetic energy which is then efficiently channeled into energetic particles and high-energy radiation. Results will be discussed in the context of gamma-ray pulsars, merging binary neutron stars and weakly accreting Kerr black holes.


"The Milky Way as seen by the OGLE survey"

Igor Soszyński (Astronomical Observatory, Warsaw University)

The Optical Gravitational Lensing Experiment (OGLE) is currently the world's largest survey aimed at searching for variability in the sky. Currently, the project monitors brightness of about two billion objects in the densest stellar regions of the sky: central regions of the Galaxy, the Galactic disk, and the Magellanic Clouds. The OGLE Collection of Variable Stars currently contains nearly one million objects of various types and this is the largest set of variable stars ever obtained by any astronomical project. Recently, OGLE has greatly extended the list of known Cepheids in the Milky Way disk and used them to explore the structure, dynamics, and history of our Galaxy. I will present these results as well as other most spectacular latest OGLE discoveries in the field of variable stars.


"Radio sources in the SDSS spectroscopic catalogues"

Dorota Kozieł-Wierzbowska (Astronomical Observatory, Jagiellonian University)

I will present the catalogue of radio sources with galactic counterparts and unresolved or extended morphologies I (ROGUE I), which is the largest, handmade catalogue of visually classified radio objects. It was created by cross-matching galaxies from the SDSS with the FIRST and NVSS catalogues. The catalogue contains more than 32,000 galaxies with a FIRST core within 3arcsec of the optical position. However, in the radio catalogues with a low flux limit like ROGUE I, the separation of objects in which the radio emission is associated with jets from the radio emission arising in the star-forming regions is a challenging task. In recent papers (Best & Heckman 2012, Sabater et al. 2019) this population separation was made based on several different diagrams. However, this procedure is complicated and requires the knowledge of many different parameters, like optical emission line luminosities or ratios, galaxy mass or Dn(4000). Therefore, during my talk I will also discuss a single diagram that can be used to distinguish radio emission produced by an active galactic nucleus from the one emitted in star-forming regions.


"Watchmaking - craft or art ?"

Eugeniusz Szwed (Polish Watch and Clock Collectors Club)