The Colloquium takes place every Wednesday at 11:15 AM - Warsaw Copernicus Astronomical Centre online by means of Zoom platform. The Colloquium is given in English and chaired by dr Stanisław Bajtlik (bajtlik@camk.edu.pl). People from outside of the Copernicus Center are very welcome to participate. For technical detailes please contact Dr. Stanislaw Bajtlik.
Maciej Zgirski (Institute of Physics, PAN,, Warsaw)
Maciej Zgirski Leader of the CoolPhon Group at MAGTOP at the Institute of Physics, Polish Academy of Sciences (IF PAN) - http://coolphongroup.ifpan.edu.pl/ zgirski@ifpan.edu.pl, +48730003175 Short CV: Maciej Zgirski (born 1979) graduated from the Faculty of Physics of Warsaw University of Technology in 2003. Defended his PhD in the field of the experimental low temperature mesoscopic physics at the University of Jyväskylä, Finland in 2008. In years 2008-2010 he joined Quantronics Group (CEA) in Saclay, France as a PostDoc. Since end of 2010 employed at the Institute of Physics, PAN in Warsaw. Since 06/2024 professor at the International Centre for Interfacing Magnetism and Superconductivity with Topological Matter (MAGTOP) at the Institute of Physics. Received habilitation in 2022 for the creation of the pioneering time-resolved low- temperature thermometry and its application for the experimental investigation of the dynamical thermal processes at the nanoscale. Specializing in thermodynamics of nanostructures with the emphasis on the fast thermometry based on the various types of superconducting Josephson junctions. Another his expertise involves building novel-concept superconducting devices based on manipulating just a single superconducting vortex. The experimental approaches, sample designs, and measuring protocols used in the CoolPhon Group are of pioneering character, and create a backbone for new applications in the field of applied mesoscopic superconductivity.
Gopal Bhatta (Institute of Astronomy, University of Zielona Góra)
X-ray emission from blazars provides crucial insights into the underlying AGN processes, as it can arise from synchrotron and inverse-Compton mechanisms in leptonic models, or be part of particle cascades produced in hadronic models. Here we present multi-instrument, multi-epoch investigations of several prominent blazars (OJ 287, PKS 2155–304, 3C 273, and Mrk 421 and samples of other blazars) with a particular focus on their X-ray variability and spectral properties. We perform comprehensive timing and spectral analyses covering intraday to decadal timescales, using long-term observations from Swift, XMM-Newton, NICER, and NuSTAR spanning more than two decades. During the period, the sources consistently display strong variability, with X-ray flux changes reaching factors of ~10–200 during major flares. Timing analysis, including fractional variability, flux and rms distributions, PSD slopes, and rms–flux relations, reveal a combination of normal, lognormal, and bimodal flux states, indicating complex, multiplicative variability processes and transitions between distinct emission states. Spectral analyses using power-law, log-parabola, and broken power-law models demonstrate that log-parabolic or broken spectra best represent the majority of observations, pointing to curvature in the underlying electron energy distributions. Several sources show clear flux-dependent spectral evolution, including “harder-when-brighter’’ behavior and strong correlations between synchrotron peak energy, curvature parameters, and X-ray flux. In OJ 287, broad-band spectral energy distribution (SED) modeling highlights systematic transitions between inverse-Compton–dominated quiescent states and synchrotron-dominated flaring states. Collectively, the observed properties such as Gaussian and non-Gaussian flux distributions, variable PSD slopes, and evolving spectral curvature supports scenarios involving energy-dependent particle acceleration, turbulence, and/or magnetic reconnection within the jet.
Journal Club takes place on Mondays at 11:15 AM in the Seminar Room. The presentation is given in English and is chaired by Journal Club Coordinators. Anyone interested in giving a Journal Club talk is encouraged to contact the email: journalclub(@camk.edu.pl).
Angelos Karakonstantakis (NCAC, Warsaw)
based on https://arxiv.org/abs/2510.13249 from Meng et al. (Oct 2025).
