The 16th International Olimpiad on Astronomy and Astrophysics (IOAA) was held in Poland from 10-20th August 2023 with representatives of over 50 countries. I will give an overview of the event and exmaples of problem tasks, the scale of the organisation and the impact the IOAA has on the astronomical community.

We demonstrate the existence of chaotic geodesics for the Einstein--Rosen standing gravitational waves. The complex dynamics of massive test particles are governed by a chaotic heteroclinic network. We present the fractal associated with the system under investigation. Gravitational standing waves produce intricate patterns through test particles in a vague analogy to mechanical vibrations generating Chladni figures and complicated shapes of Faraday waves.

Most galaxies comparable to or larger than the mass of the Milky Way host hot, X-ray emitting atmospheres and accreting supermassive black holes. I will present results based on radio and X-ray observations, which indicate that in massive early-type galaxies the central radio sources are mostly switched on, and the mechanical jet power correlates with the mass of the central black hole. I will introduce the QUVIK (Quick Ultra-VIolet Kilonova surveyor) mission, which has recently been approved for funding. QUVIK, a Czech national science and technology mission, is a UV space telescope designed to study the energetic transient sky. The mission will also provide unique opportunities for studying accreting black holes, including reverberation mapping, tidal disruption events, and peculiar sources in galactic nuclei.

Radio galaxy jets strikingly remain straight and collimated for distances ranging from a few kiloparsecs to megaparsecs for millions of years. However, since the advent of deep sky surveys, the discovery of radio galaxies with bent radio jets has been ever-increasing. These sources, classified as X-shaped or S-shaped, signify a dynamic interplay between the radio jets, the central active region, and the intergalactic medium. The evolution of such radio sources is explained using several theoretical models, including galaxy mergers, but direct evidence has remained observationally sparse. In this talk, I will present multifrequency observations and radio analysis of a few such sources and discuss the possible mechanisms behind their formation.

The X-ray continuum emission of active galactic nuclei (AGN) may be reflected by circumnuclear dusty tori, producing prominent fluorescence iron lines at X-ray frequencies. I will present the results of broad-band emission modeling for three radio-loud AGNs belonging to the class of Compact Symmetric Objects (CSOs). These AGNs, identified as J1511+0518, OQ+208, and 2021+614, exhibit narrow Fe Kα lines and high intrinsic X-ray absorbing column densities. We argue that the intrinsic X-ray continuum in all these sources can be attributed to the inverse-Compton emission of compact radio lobes. Furthermore, we propose that the observed iron lines may be generated by the reflection of the lobes' continuum off the surrounding cold dust.

The X-ray continuum emission of active galactic nuclei (AGN) may be reflected by circumnuclear dusty tori, producing prominent fluorescence iron lines at X-ray frequencies. I will present the results of broad-band emission modeling for three radio-loud AGNs belonging to the class of Compact Symmetric Objects (CSOs). These AGNs, identified as J1511+0518, OQ+208, and 2021+614, exhibit narrow Fe Kα lines and high intrinsic X-ray absorbing column densities. We argue that the intrinsic X-ray continuum in all these sources can be attributed to the inverse-Compton emission of compact radio lobes. Furthermore, we propose that the observed iron lines may be generated by the reflection of the lobes' continuum off the surrounding cold dust.

Pulsar observations using the PL611 Polish LOFAR station in Łazy started in 2017, and regular observing projects a year later. Since then we observe pulsars almost every week for c.a. 30 hours fully utilizing the station's stand-alone time. The main research project was focused on the monitoring of the influence of the Ionized Interstellar Medium (IISM) on the pulsar signals via the means of observations of interstellar scattering and dispersion measure variations. Such observations were only rarely conducted for individual pulsars before, and almost never for a period exceeding a year or two. This means that the data we gathered provides an excellent opportunity to not only study the scattering and dispersion effects for the observed objects, but also - through the estimations of the variability of related parameters - it will allow us to make one of the first insights into the anisotropy and inhomogeneity of the IISM. Recently we also started another observing program: the study of individual pulses, which yields interesting results that are important for the understanding of the pulsar emission mechanisms. These observations clearly show, that interesting and innovative research can be performed with relatively small radio telescopes, such as a single LOFAR station.

Shock waves in cosmic plasma are usually assumed to be a places of particle acceleration. They can be observed in different astrophysical objects at widely varying scales, up to large-scale shocks in the clusters of galaxies. In this case, the galaxy merger shocks are found to generate X-ray and radio emission, that indicate the efficient electron acceleration at these objects. Typically, merger shocks propagate in relatively hot plasma with plasma beta β >> 1 at low Mach numbers, M << 10. The detailed mechanisms of the particle acceleration at such conditions are not fully understood yet. Recent studies indicate that Shock Drift Acceleration (SDA) accompanied by the particle-wave interaction can be responsible for the initial electron energization here. Our last investigations with use of the large-scale 2D Particle-In-Cell (PIC) simulations demonstrate the important role of the multi-scale wave structures, especially the ion-scale shock rippling modes, in the electron acceleration at low-Mach-number hi-beta shocks. We showed that the main mechanism of the electron acceleration at such conditions is stochastic SDA (or SSDA). Its dependence on the pre-shock plasma conditions is also studied. Although we do not observe direct transition to the Diffusive Shock Acceleration (DSA), which could produce particles with highest observed energies, the SSDA nevertheless looks like a plausible mechanism for the electron injection to DSA.

In the Lambda-CDM cosmology galaxies are thought to form through the hierarchical merging of smaller structures, hence galaxy mergers provide crucial insights into how galaxies evolve over time. The merging process can trigger star formation, feed supermassive black holes which may affect galaxy morphology. This work aims to find if it is possible to create a technique to conduct a classification of merging and nonmerging galaxies with machine learning approach using Convolutional Neural Network. One can use visual inspection to define the stage of a merger, but this method is not easily reproducible and is mostly subjective. Recent studies have shown that it is possible to use machine learning methods to address this problem. Around 500000 i-band (standard SDSS filter, 7480Å) images of size 128 x 128 pixels used for this study come from Next Generation Illustris Simulations (IllustrisTNG), a cosmological gravo-magnetohydrodynamical simulations. Our previous research shows that information is not easily extracted from the raw images by CNN, which is why this time our neural network has been fed with processed images. We created models of each galaxy on the images. Sersic profile of each galaxy has been subtracted from the original images to leave behind everything that does not match the profile. During the talk, we will discuss how the models were made and how their subtraction from the original photo affected the results.

This presentation provides an overview of neutrino astronomy, focusing on key aspects such as neutrino physics fundamentals, historical milestones in neutrino research, detector mechanisms, and recent results from KM3NeT and IceCube experiments. Through precise analysis of neutrino signals, these experiments shed light on astrophysical phenomena, offering crucial insights into the universe's most elusive and energetic events.

Hot subdwarf B stars (sdB) are stellar objects at the late stage of their stellar evolution. These helium burning objects are the product of excessive loss of hydrogen envelope before the helium flash. The origins of these objects are believed to arise from binary interactions, with three primary formation channels proposed: common-envelope ejection (CEE), stable Roche-lobe overflow (RLOF) mechanism, and the merger of two low-mass white dwarfs (Han et al., 2002, 2003). These objects are crucial for studying the late stages of stellar evolution, binary interactions, and stellar interiors, particularly through the analysis of their pulsations. Current research indicates that approximately 60% of identified sdB stars are located within binary systems. Depending on the interactions between the sdB and its companion, these binaries are divided into two main groups, the systems with long orbital periods (longer than one year) produced in a stable RLOF, and the short period systems (order of hours) which evolved via the CEE. In this presentation I will provide an overview of my work with analysis of these sdB stars in binary systems. That is, from observations to the modeling of their light curves.

Gravitational waves (GW) from compact objects offer crucial insights into their astrophysical origins. However, most GW waveforms rely on quasi-circular templates, presenting challenges for future detections and interpretations. Effects like eccentricity, impacting GW waveforms, are garnering interest in terms of their detectability by GW detectors. This talk will first present an overview of GW theory and data analysis, then delve into the role of eccentricity in the formation channels of compact binaries. Finally, it will briefly introduce optimization techniques used in eccentric gravitational wave searches. A portion of this talk is tailored for a younger audience as an introduction to GW research.

All except one mass transfer episode in the isolated binary evolution channel occur at short timescales and, hence, are difficult to observe. This leads to many unconstrained assumptions in modelling mass transfer phases. The uncertainties percolate through our understanding of progenitors of stripped-envelope supernovae and gravitational wave mergers. As the only exception, the nuclear-timescale so-called 'slow Case A' mass transfer phase in short-period binaries have many Algol binaries as observational counterparts. Since a thermal timescale mass transfer precedes the slow Case A phase, in-situ constraints on stellar and binary physics assumptions, such as mass transfer efficiency, tidal strength and internal mixing, can be obtained through population synthesis studies of massive Algols. I will discuss the current state-of-the-art modelling and observations of these binaries and our identification of a novel outcome from this binary evolution channel, namely the 'reverse Algols'. We identified semi-detached binaries where the more massive star transfers mass to a less massive companion on a nuclear timescale. We also found that binary stripping can form Wolf-Rayet binaries on the main sequence with identified observational counterparts. Our population synthesis results predict ~5% of massive binaries (30-90 Msun) in the main sequence in the above configuration.

Prof. Zbigniew Postawa is the cadidate for the position of Dean of WFAiIS, who expressed his wish to meet with our Observatory community, the Observatory Council members in particular, and discussions on expectations towards future dean authorities. The meeting will be held mostly in Polish, but there should be a possibility to discuss some issues in English.

Luminous and Ultra-luminous Infrared Galaxies (U/LIRGs) are extreme star-forming galaxies triggered primarily by interactions and mergers between gas-rich galaxies. They play a crucial role, particularly at higher redshifts. U/LIRGs are the primary contributors to the co-moving star formation rate density (SFRD) of the Universe at z > 1, making them extremely important sources for studying galaxy formation and evolution. Further, the bulk infrared emission in these galaxies is due to warm dust heated by active galactic nuclei (AGN), starbursts due to major mergers, or both. This correlates well with the widely accepted evolutionary picture, which places U/LIRGs at a fixed stage in the evolutionary sequence between the transformation of gas-rich galaxies and red-dead elliptical ones. Therefore, they provide excellent nearby laboratories for studying in detail the physical processes associated with the hierarchical transformation of star-forming galaxies into elliptical galaxies. The spectral energy distribution (SED) of a galaxy contains the imprint of the baryonic processes that drive its formation and evolution along cosmic times. Detailed SED modeling of nearby U/LIRGs is, therefore, important for gaining a better understanding of baryonic processes and developing testing models that can be used to explain statistical studies based on large populations of such galaxies at high redshift. I will discuss the global astrophysical properties of a sample of 25 starburst galaxies, combining the SED modeling results of 11 LIRGs and 14 ULIRGs with photometric data from the literature covering ultraviolet-far-infrared and radio bands (~50 MHz to ~30 GHz). Further, I will focus on bridging the gap between ultraviolet (UV)-infrared(IR) and radio SED modeling for galaxies, which have traditionally been pursued independently in order to discuss the interconnectedness of underlying astrophysical processes.

Recent studies have shown that triple stars can explain a lot of evolutionary phenomena like the formation of blue stragglers, intermediate mass BH, Thorne-Żytkow object, asymmetry of PNe etc. A special class of triple stars, compact hierarchical triple (CHT), helps us constrain the physics of dynamical evolution on a shorter timescale. CHTs have a tertiary in an orbit of a period less than 1000 d. This allows us to observe and study the dynamics and stability of these systems. A low-mass CHT is also analogous to multi-planetary systems as all three stars are contained in a scale of 5 AU. Understanding these systems will give us insights to a lot of problems in stellar and planetary astrophysics. In our project, we use CHTs with eclipsing binary (EB) to extract stellar, orbital, and atmospheric parameters of the component stars. We use photometry and spectroscopy, along with complex methods of analysis to extract all the parameters. Using the parameters we constrain the ages of the systems. Coupled dynamical and stellar evolution simulations help us check the stability of the systems. Finally, using such detailed parameter estimates we try to constrain formation scenarios of these rare class of multiple stars.

The advent of LoFAR in recent years offers superior sensitivity and resolution at low frequencies, allowing us to discover more giant radio galaxies (GRGs) than ever before. Although statistical analyses of the GRG population are currently advanced, detailed multifrequency examinations of individual objects cover only a small number of them. Such detailed analysis demands multifrequency data that spans a broad spectrum from low to high frequencies, matched in sensitivity and spatial resolution. GRGs exceeding 2 Mpc in size are rare, constituting less than ~10% of the GRG population. Consequently, we have selected a sample of the largest and brightest GRGs, all exceeding 2 Mpc, totaling eight sources (7 GRGs and 1 GRQ). These sources were meticulously observed using LoFAR, uGMRT, and JVLA, covering a frequency range from 150 MHz to 10 GHz. In this presentation, I will describe the methods used and discuss the interesting results we obtained.

The analysis of the data published by Gaia collaboration in June 2022 led to the discovery of the first two dormant (no X-ray emission detected) black hole (BH) binaries: Gaia BH1 and Gaia BH2. The wide and eccentric orbits along with the low mass of the luminous companion in those systems challenge the known formation scenarios of BH binaries. In my presentation I will discuss the two competing scenarios for the evolution of Gaia BH1 and Gaia BH2: the isolated binary evolution scenario and the dynamical interactions in the young, massive open stellar clusters scenario. Within the isolated binary evolution scenario I will also focus on the influence which may have the magnitude and the direction of the natal kick imparted to the BH by the SN explosion on the formation of dormant BH binaries.

Compact pulsating stars, including hot subdwarfs and white dwarfs, represent the final evolutionary stage of low- and intermediate-mass stars. They play a unique and fundamental role in enhancing our understanding of the formation and evolution of stars, the dynamics of binary and planetary systems, and the complexities of stellar atmospheres and interiors.Compact pulsating stars display variations in brightness with periods ranging from about 100 to 14,000 seconds and these variations can reach amplitudes of up to 0.4 magnitudes in both types of stars. The most effective method for detecting and analyzing these subtle fluctuations is continuous high-cadence time-series photometry. Over the past decade, space missions such as Kepler, K2, and currently NASA's Transiting Exoplanet Survey Satellite (TESS) have significantly enhanced our understanding of pulsating, highly evolved compact stars. These advancements are driven by improvements in high-precision and high-duty cycle photometric monitoring from space, enabling unprecedented asteroseismic measurements and tools for studying pulsating hot subdwarfs and white dwarfs.In this review talk, I will explore the crucial role of asteroseismology in studying these pulsating compact stars. I will cover the latest developments in observational techniques and theoretical models that have greatly advanced our understanding of hot subdwarfs and white dwarfs. Additionally, I will highlight the significant contributions of ground-based telescopes and space missions to the field of asteroseismology and consider future prospects that may transform our knowledge of these fascinating stellar remnants.

In recent years, spins of merging black holes have been relatively accurately measured based on their gravitational-wave signals. Their are generally low, with the estimated average spin parameter as low as 0.06. 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. >0.9985 at 3 sigma in Cyg X-1. I will present our recent results regarding this discrepancy. In particular, I will discuss possible systematic effects affecting the spin measurements in accreting systems and whether they can be reconciled with those based on mergers.

It is now widely accepted that active galactic nuclei (AGN) are powered by the efficient conversion of gravitational energy into radiation due to accretion onto a supermassive black hole (SMBH). This accretion occurs via an accretion disk (AD), which is responsible for the majority of UV to optical emission in the spectral energy distributions (SEDs) of AGN. The broad-line region (BLR), which emits the broad emission lines typically observed in the spectra of Type I AGN, is believed to exist in close proximity to the (outer) AD. However, the direct connection between these two entities remains unknown. Only 3-10% of the AGN population exhibit double-peaked emission line profiles, which are considered direct kinematic signatures of a rotating gas disk. In this talk, I will present results from recent spectroscopic variability campaigns that have allowed us to determine structural properties of the outer AD through detailed analysis of emission line profiles. I will discuss the implications for the AD and BLR complex and how future high-quality observations might be key to probing the BLR and outer AD in AGN in unprecedented detail.

Understanding the physical characteristics of nearby galaxies, such as the pure-starburst galaxy NGC 253, is crucial for gaining insights into extreme interstellar medium (ISM) conditions at high redshift and for advancing our knowledge of galaxy formation and evolution over cosmic epochs. Recent advancements in ground- and space-based instruments have provided an unprecedented legacy of multi-wavelength data. To fully exploit this wealth of information, it is essential to extract insights from the spectral energy distribution (SED).
In this talk, I will present the results of the first-ever spatially resolved (3", ~51 pc) multi-wavelength SED of an extragalactic source, covering a broad range from optical to radio wavelengths. Our study focuses on the central molecular zone (CMZ) of the well-studied nuclear starburst galaxy NGC 253, with particular attention to the extreme star formation processes occurring within its ten giant molecular clouds (GMCs), which contribute significantly to the galaxy's overall star formation activity.
Further, I will discuss the results of the characterization of stellar optical spectra, shedding light on the star formation processes and ISM conditions within NGC 253. Additionally, we explored metallicity indicators within the central GMC, marking a significant step forward in understanding the complex chemistry of extragalactic environments. This work facilitates a direct comparison of ISM conditions between NGC 253 and analogous regions within our own Milky Way. Looking ahead, the study sets the stage for future investigations using data from the James Webb Space Telescope and high-resolution ALCHEMI observations, promising to deepen our understanding of galaxy evolution and star formation across cosmic time.