Arthur Puls (CAMK, Warsaw)
Heavier elements (atomic number larger than ~30) are produced in stellar nucleosynthesis by neutron-capture, which is known to happen either by the r- (rapid) process and the s- (slow) process. In the context of Galactic Chemical Evolution, the elements in the third r-process peak (Os, Ir, Pt) are among the least studied species of the periodic table. This is due to observational challenges: the lines of these elements featuring in stellar spectra are weak, in crowded wavelengths, and appear in cool (FGK-type) stars, in which those (blue, near-UV) wavelengths have relatively low flux. In this talk, I will present the results of the first study focusing on a homogeneous set of stellar abundances for the third r-process peak, which more than doubled the availability of Os, Ir, Pt stellar abundances from high resolution spectra in the literature. The implications of the results for our understanding of the nature of the r-process, both in terms of physics and astrophysical sites, will also be discussed.
winter break
winter break
CAMK Annual Meeting
Tomasz Miller (Copernicus Center, Jagiellonian University, Cracow)
In the late 19th century, Georg Cantor made a stunning discovery: in mathematics there is not just a single infinity, but an infinite hierarchy of "transfinite numbers." In my talk, I will briefly recall how this "Cantor’s paradise" (as Hilbert called it) is constructed. I will then turn to a more recent attempt to tame infinity, initiated by John H. Conway, who went on to discover an even richer - in a sense "ultimate" - number system: the surreal numbers. This system contains not only Cantor’s transfinites but also their reciprocals, the infinitesimals. I will close by reflecting on a natural question: why study such abstract objects at all?
Andrzej Zdziarski (CAMK, PAN, Warsaw)
In recent years, spins of merging black holes have been measured with relatively high accuracy from their gravitational-wave signals. They are generally low, with the estimated average effective spin parameter close to null. On the other hand, spins of many accreting black-hole binaries have been measured to be high, some close to the maximum spin parameter of 1, e.g., greater than 0.9985 at 3 sigma in Cygnus X-1. I will present our recent results regarding this discrepancy. In particular, I will discuss possible systematic effects affecting spin measurements in accreting systems and whether they can be reconciled with those from gravitational-wave observations. See New Astronomy Reviews (2026), 102, 101746 (arXiv:2506.00623).
Arpita Misra (Jagiellonian University, Cracow)
Supermassive black hole (SMBH) spin plays a central role in shaping relativistic jets, yet direct measurements of spin and its evolution remain challenging. Radio jets provide an indirect yet powerful probe of SMBH spin dynamics through their morphology, orientation, and temporal behavior. The radio galaxies exhibiting X-shaped or S-shaped jets are key candidates to study the spin evolution as they highlight a dynamic interplay between the jets, the central active region, and the intergalactic medium. In this talk, I will present observational evidence linking the jet properties of winged radio galaxies to the evolving spin of SMBHs, primarily focusing on S-shaped radio galaxies. Using multiwavelength and multi-frequency radio data, I will discuss how features such as jet reorientation, spectral aging, and large-scale morphology in post-merger and merging systems offer insights into changes in the spin axis. These results highlight the role of radio jets as tracers of SMBH spin evolution and demonstrate how detailed radio studies can constrain the physical processes governing black hole growth and feedback across cosmic time.
Daniela Turis-Gallo (Universidad de Valparaiso, Chile)
Massive stars play a fundamental role in stellar evolution, feedback processes, and the chemical enrichment of galaxies. However, determining their fundamental parameters remains challenging because strong rotational effects, such as stellar deformation and gravity darkening, significantly modify their observed spectra. I will present a model-based spectroscopic analysis of rapidly rotating massive stars that consistently accounts for stellar oblateness and gravity darkening. Using synthetic spectra generated with the ZPEKTR code, we derive stellar parameters—in particular, the inclination angle and equatorial rotation velocity—from photospheric lines. I will analyse the intrinsic limitations of the ZPEKTR code as a function of stellar rotation rate, identifying the parameter space in which the models remain reliable and in which systematic uncertainties become significant. I will also show the application of the code to a sample of Be stars observed with high spectral resolution. Our results are compared with independent determinations from the literature, including interferometric measurements, providing a critical assessment of the accuracy of spectroscopic methods.
Juan Pablo Hidalgo (University of Rome)
Large-scale magnetic fields have been observed in about 10% of main-sequence early-type stars. Notably, chemically peculiar Ap/Bp stars can host surface magnetic fields with mean strengths between 200 G and 30 kG. Unlike late-type stars, whose magnetic fields have complex geometries and are likely generated by convective dynamos, the observed magnetic fields of early-type stars have simpler geometries, and are stable over long timescales, with virtually no variability over several decades. Because these stars have thick radiative envelopes and convective cores, surface dynamos are unlikely to account for the observed magnetism. Consequently, the origin of these magnetic fields remains uncertain. In this talk, I will review recent progress in some of the main theories proposed to explain the magnetism in early-type stars, exploring dynamos hosted by their convective cores, and their interaction with fossil fields inherited from earlier evolutionary stages. Furthermore, I will discuss ongoing simulations of pre-main-sequence stellar evolution aimed at constraining the structure and properties of these primordial fields.
Bogumił Pilecki (CAMK, Warsaw)
Dominika Król (Harvard Smithonian CfA)
Maciek Wielgus (Instituto de Astrofísica de Andalucía, IAA-CSIC, Granada, Hiszpania)
Laetitia Gibaud (Department of Physics, University of Białystok)
Samik Mitra (Astrophysics and Relativity Group International Centre for Theoretical Sciences, Bengaluru, India)
