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.
Kamil Bicz (University of Wrocław)
Leda Berni (INAF- Osservatorio Astrofisico di Arcetri (Florence, Italy))
The Λ-CDM scenario predicts that the Milky Way assembled hierarchically, through the accretion of smaller systems such as globular clusters and dwarf galaxies. Although these systems can be disrupted by tidal interactions, their remnants survive as stellar streams that retain chemical and dynamical signatures of common origin. We developed CREEK, a machine-learning pipeline that learns similarity relations between stars using siamese neural networks, models their relational structure with graph neural networks autoencoders, and identifies substructures through density-based clustering (OPTICS). Applied to halo stars, our method recovers 80% of known globular clusters in the dataset, re-identifies established stellar streams, and reveals a candidate new substructure. We also detect two distinct populations within the Gaia Enceladus stream, possibly linked to multiple accretion passages through the Milky Way. The CREEK thus represents an objective and data-driven method for the selection of stars belonging to streams and to stellar structures in general, and the results highlight the capabilities of machine learning to find relations that would escape a classical search.
Dominika Król (Harvard Smithonian CfA)
One of the crucial parameters characterizing the interstellar medium (ISM) is its metallicity, which is associated with the chemical evolution of a galaxy’s stellar populations. However, stellar feedback is only part of the story. The extent to which active galactic nuclei (AGN) influence the chemical evolution of their hosts remains an open question. In my talk, I will present spatially resolved metallicity (log(O/H)) maps for Mrk 573, a Compton-thick AGN. By applying theoretical metallicity diagnostics tailored to AGN-driven emission to Hubble Space Telescope (HST) data, we probe the metallicity out to ~1 kpc scales, with tens-of-parsecs resolution across the ionization bicone. We find significant metallicity enhancement in AGN-dominated regions, with oxygen abundances reaching up to ~3xSolar, strongly correlated with the Seyfert/LINER Index, defined as the distance of a point from the Seyfert/LINER division line in the S-BPT diagram. Metallicity enrichment traces trace the VLA 6~cm jet/radio lobe emission. This, together with the lack of evidence for star formation in the bi-cone region, suggests that the enrichment originates from metals transported from the nuclear AGN region by winds, outflows, or jets. I will discuss the possible sources and implications of this metal enrichment.
Martin Solar (Adam Mickiewicz University, Poznań)
Core-collapse supernovae are very energetic explosions that have a significant impact in the interstellar medium within galaxies. However, it is not well understood how progenitors of core-collapse supernovae form, evolve, and explode. In this talk, I plan to constrain the core-collapse supernova progenitor properties studying their star formation efficiency (or molecular gas depletion time) environments. In summary, it is found that interacting massive binaries occur in regions of intense, efficient star formation rather than simply higher gas content.
Biswaraj Palit (NCAC, Warsaw)
Kamil Bicz (University of Wrocław)
Przemysław Mróz (Astronomical Observatory, Warsaw University)
Maciek Wielgus (Instituto de Astrofísica de Andalucía, IAA-CSIC, Granada, Hiszpania)
Patrick C. Fragile (Charleston College)
Accretion of gas onto black holes is one of the most important processes shaping our Universe. Understanding extremely high rates of accretion (dubbed `super-Eddington') is vital to explaining the challenging observation that supermassive black holes (SMBHs) are fully formed at redshifts >7. It is also important to understanding astrophysical objects such as tidal disruption events (TDEs) and ultra-luminous X-ray sources (ULXs). While we are able to perform observations of super-Eddington accreting systems, to understand them more fully, we must turn to numerical studies. In this talk, I will present the results of some recent super-Eddington disk simulations and discuss some of the interesting things we are learning.
Bogumił Pilecki (CAMK, Warsaw)
Samik Mitra (Astrophysics and Relativity Group International Centre for Theoretical Sciences, Bengaluru, India)
