List of abstracts
2026

In this new era of high-energy spectro-polarimetry, our understanding of high-energy sources has the potential to be greatly improved. This is especially the case for Black Hole X-ray Binaries (BHXB), also known as Microquasars, for which many unresolved challenges remain. In particular acceleration mechanisms and how they relate to accretion-ejection processes. Combined with spectroscopy, polarization is a powerful tool to reveal the geometry of the system and the configuration of the magnetic fields. The persistent Microquasar Cygnus X-1 is particularly well suited for our analysis. In soft X-rays, the polarization is low and aligned with the general direction of the jet, while the polarization angle in the soft gamma-rays is found close to 70° away from the jet. We use a novel method to combine high-energy spectra and polarization of this bright source from 1 keV to 2 MeV in a single fit, including observations from IXPE, PoGO+, XL-Calibur, AstroSat, INTEGRAL/SPI and INTEGRAL/IBIS. Our study involves energy-dependent polarization models for both emission processes, in part inspired by similar studies on Blazars. Preliminary results already reveal new constraints about the non-thermal hard-tail origin (above 100 keV), in particular its high-energy spectral cut-off and the degree of order of the magnetic field.

The Andromeda galaxy (M31) is a promising target for the indirect search of dark matter (DM) due to its proximity and expected massive DM halo. It functions as test case for a Milky Way (MW) like galaxy as the isotropic emission from the MW halo itself cannot be detected with a coded mask telescope like INTEGRAL/SPI. MeV data can put strong limits on DM models from the MeV up to the TeV mass range since weakly interacting massive particles also produce a significant flux of secondary MeV photons from inverse Compton scattering and positron annihilation. We analyze the spectrum of M31 obtained with the SPI instrument to constrain DM models. From the 511 keV emission from positron annihilation, we estimate the pair production rate in M31 to derive a lower mass limit on thermal DM. We further constrain the parameter space for DM annihilation and decay into electron–positron pairs, and place limits on primordial black hole DM.

The Cosmic Photon Background (CPB), an isotropic radiation field spanning the full electromagnetic spectrum, provides a potential source of positrons through photon–photon interactions (pair production). To model the CPB, it is decomposed into a set of gray-body components that evolve with redshift according to source-specific luminosity functions. The pair-production rate is obtained by integrating the angle- and energy-dependent cross section over the evolving photon field. The generated electron–positron pairs are then propagated to the present epoch (z = 0), accounting for cosmological expansion and energy losses in the intergalactic medium. The resulting photon emission is computed at each redshift and integrated along the line of sight to determine its contribution to the present-day Cosmic Gamma-Ray Background (CGB). The pair-production emissivity rises steeply from ~2.0 × 10⁻³⁶ s⁻¹ cm⁻³ at z = 0 to a peak of ~1.8 × 10⁻³¹ s⁻¹ cm⁻³ at z ≈ 2.7, followed by a decline at higher redshifts. This corresponds to a total cosmic pair-production rate of order 10⁵⁴ positrons per second up to z = 10. The secondary emission from inverse Compton scattering of these pairs off the CPB yields a significant contribution to the CGB. In particular, in the 1–10 MeV energy range, this component may account for approximately 10–20% of the total observed gamma-ray background. These results indicate that cosmological γ–γ absorption sets a minimum level of secondary emission that must be included in models of the CGB, especially in the MeV regime.

Originally, the IBWS (INTEGRAL/BART) workshops focused on the work of High energy astrophysics group (at that dime dominated by young research fellows and students) in Astronomical Institute of the Academy of Sciences of the Czech Republic and relevant national and international collaborators from the field, with intensive student participation. During the early years, these activities were focussed on the ESA INTEGRAL satellite and on the related ground-based robotic telescopes, e.g. the small robotic BART telescope at the Ondrejov Observatory. Nowadays, the IBWS workshops promote regional collaboration in galactic and extragalactic high-energy astrophysics, both experimental as well as theoretical, with an emphasis on the interface between satellite projects and ground-based experiments (e.g. robotic telescopes). We continue our emphasis on wide participation and presentations of students and young research fellows.

Galaxy evolution over time remains unclear, with ongoing debate about how collisions affect star formation and metallicity. The role of the local environment shaped by the large-scale structure of the Universe in galaxy mergers may be significant, yet it has not been thoroughly examined. Using the IllustrisTNG cosmological simulation, we processed the catalog data and merger tree files of the TNG300-1 run. We calculated the average star formation rate (SFR) and stellar mass of galaxies over the redshift range 0 < z < 15 to trace the cosmic star formation history and galaxy growth. We investigated the environments of galaxy mergers with a focus on local density within the cosmic web, and found that interactions with gas-rich dwarf galaxies can trigger a resurgence in gas supply, highlighting the importance of gas dynamics in sustaining star formation. We compared our results with recent JWST observations and identified differences in the star formation rate density (SFRD) history between simulations and observations, providing new insights into early galaxy formation and evolution. See Koncz et. al. Universe 2025, 11(9), 286.

The origin of the Galactic 511 keV positron annihilation line has been a mystery for five decades. One proposed explanation is positron production in stellar flares, motivated by the detection of the 511 keV line in solar flares and by the association of this emission with old stellar populations. In this work, we explore this scenario using two complementary approaches. First, we build a theoretical model to estimate the quasi-persistent 511 keV emission from flaring stars. Starting from solar flare observations, we construct empirical scaling relations between flare energy and 511 keV luminosity and extend them to Galactic stellar populations using flare-frequency-energy distributions for different spectral types. In parallel, we analyze INTEGRAL/SPI data in the 511 keV band using combinations of known point sources and simple spatial templates, such as disk and bulge components modeled as two-dimensional Gaussians. We also test alternative descriptions in which no bulge template is assumed and the emission is instead described by a disk component together with a population of globular clusters, scaled by their masses and distances. This ongoing work aims to assess whether stellar flares can plausibly account for the observed Galactic 511 keV emission.

Galactic cosmic rays are widely believed to originate from shock acceleration in supernova remnants; however, observations of ionization rates in the interstellar medium (ISM) in the inner Galaxy suggest the presence of additional, potentially unknown, acceleration sources. Low-energy cosmic rays (LECRs) excite nuclei in the ISM, producing MeV gamma-ray line emission through subsequent de-excitation, and observations of this emission enable robust constraints on the LECR flux and its spatial distribution. We model the MeV gamma-ray spatial distribution using three-dimensional computation based on cosmic-ray spectra predicted by GALPROP. We then evaluate their detectability relative to non-thermal leptonic emission components and identify the locations where it can be detected by current and future MeV gamma-ray missions.

The detection and monitoring of high-energy emission from astrophysical sources provide key insights into energetic processes such as accretion, magnetic activity, and feedback in star-forming environments. Wide-field high-energy survey missions, such as the proposed THESEUS mission, are designed to perform repeated observations of large fractions of the sky, primarily targeting transient phenomena including gamma-ray bursts. As a consequence of their survey strategy, such missions also enable systematic, time-domain coverage in the soft X-ray regime, opening new opportunities for studying Galactic sources, including nearby star-forming regions and young stellar objects. We aim to assess the observability of nearby star-forming regions within the baseline survey strategy of wide-field high-energy missions and to explore how their temporal sampling can be used to characterize variability and feedback processes. In addition, we consider the synergy with ultraviolet facilities, such as ULTRASAT, which provide complementary constraints on stellar radiation fields and winds. By combining high-energy and UV time-domain coverage, it becomes possible to investigate the coupling between energetic processes in young stars and their impact on the surrounding interstellar medium.

The isotopes 26Al and 60Fe show short lifetimes (∼ 106 yr) with respect to the time scales of Galactic evolution and are therefore used as messengers of ongoing nucleosynthesis and star formation in the Milky Way. The production of both isotopes is commonly associated with massive stars. They are thought to be ejected in their supernovae, and in the case of 26Al partially in the wind phase of the star. Because of their similar origin and lifetimes , the ratio 60Fe/26Al of their γ-ray emission would be independent of the true location and distribution of their source, and yields a chance to test the outcome of stellar evolution models. The expected results of 60Fe/26Al for core-collapse supernovae, however, show discrepancies with measurements (Spyrou et al. 2024). This method only works, if 26Al and 60Fe have the same origin throughout the Galaxy. At the same time recent results from 26 Al measurements suggest a star formation rate (SFR) of ≳ 5 M⊙/yr (Siegert et al. 2023), which exceeds other literature values. Classical novae are also believed to produce 26 Al, which, if the contribution is large enough, would decrease the SFR from the correlation of 26 Al with massive stars. We aim to determine the 26 Al mass as a function of Galactocentric radius and compare it with two Galactic chemical evolution (GCE) models (Vasini et al. 2025; Martinet et al. 2022) to estimate the contribution of (very) massive stars and classical novae. We are using 20 yr of INTEGRAL/SPI observations of the decay gamma-ray line at 1. 809 MeV to test different assumptions on the radial structure of 26 Al. We present the total mass, the Galactic distribution of the 26Al, and the relative contribution of 26Al assuming different Galactic 3D models. We find significant contributions from classical novae which exceed prior studies for all tested models. A larger contribution of 26Al from classical novae directly decreases the effective 60Fe/26Al ratio affects the interpretation as a probe of massive-star nucleosynthesis and would lower the SFR from 26Al γ-ray measurements accordingly to 1-2 M⊙/yr

Since the typical lengths of the recurrence times Tc (cycle lengths) of outbursts in soft X-ray transients (SXTs) range from months to decades, X-ray monitors are needed to detect them and investigate their evolution. Evolution of Tc shows a complex curve with episodes of increase and decrease. Significant results can be obtained even when different monitors with various energy bands, available for the individual time segments (years or decades), are used (e.g., ASM/RXTE, MAXI/ISS, BAT/Swift). The character of the O-C curves of SXTs bears a striking similarity to that of dwarf novae observed in the optical band. It means that variations in Tc are large, but generally not chaotic, and long-term trends in the O-C curves can be resolved. Observing the variety of the X-ray evolution of dwarf novae is still limited by the low sensitivity of the current X-ray monitors.

In neutron star low-mass X-ray binaries, the boundary layer beneath the accretion disk is likely a major source of irradiation of the inner disk. Because this illuminating geometry differs from the compact corona usually assumed in relativistic reflection models, the radial profile of disk-incident flux may also depart from standard prescriptions. We investigate the illumination of a thin accretion disk by a latitude-dependent spreading layer on the surface of a weakly magnetized neutron star and find that the resulting radial dependence is well described by a smoothly broken power law, with parameters that depend systematically on the spreading layer geometry.

Most models used to fit Fe-K lines in neutron star systems assume that such emission lines come from the accretion disk alone and neglect the presence of stellar surface. This simplification omits obscuration effects and possible iron line emission from the surface, where shear-heated material cools and spreads. Here, we present a relativistic model that incorporates both components consistently. Using full relativistic ray tracing code LSD, we compute photon trajectories from the disk and the neutron star surface. We demonstrate that neglecting the presence of the neutron star itself can lead to biased interpretations of relativistic iron emission line profiles. We show that such profiles are degenerated with pure disk emission for different disk parameters.

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The FRAM robotic telescopes started as experimental tools for atmospheric monitoring at astroparticle observatories over two decades ago. Over time, both their purpose and methods have greatly changed, sometimes following unexpectedly twisting paths. The original design target of the FRAM at the Pierre Auger Observatory was the measurement of wavelength dependence of aerosol extinction using photoelectric measurements of bright stars. After this has proven prohibitively difficult, the program re-focused on rapid cloud detection along the apparent trajectory of interesting cosmic ray showers - and during these observations, the breakthrough method of aerosol measurement using wide-field photometry was developed, leading to the expansion of the FRAM project to support the upcoming Cherenkov Telescope Array Observatory. Eventually, we went full circle: using the exceptionally stable conditions at Roque de los Muchachos, we can now show that the wide-field method is actually the right way for the wavelength-dependence measurement. As this quantity is directly correlated with the size of the aerosol particles, we are here opening a new window for atmospheric physics at night, with possibly broad application far beyond simple atmospheric monitoring.

The increasing use of CubeSat platforms requires reliable and cost-effective radiation monitoring solutions. This work presents the development of a COTS-based ionizing radiation monitoring payload for small satellite applications, targeting continuous in-orbit environmental characterization without the use of expensive rad-hard components. The payload is designed within a modular CubeSat architecture and utilizes volatile and non-volatile memory elements as radiation-sensitive components. The measurement concept is based on correlating radiation flux with error rate variations, enabling indirect dosimetry. The work focuses on the system architecture, payload design, and the definition of calibration and testing procedures. The presentation introduces the developed payload concept and outlines its integration into a CubeSat platform, highlighting key design considerations and challenges relevant to university-led small satellite missions.

We present the Phase B planning of the Transient High-Energy Sky and Early Universe Surveyor (THESEUS) Infrared Telescope’s Calibration Unit, carried out during Phase A, with emphasis on LED-based calibration concepts and optical design considerations. The work outlines a structured testing strategy that combines individual device characterization with batch-level validation to ensure consistent and reliable performance. In parallel, we investigate how different LED configurations and mounting approaches influence the optical behavior of the system. Ray-tracing simulations are used to explore light propagation and assess potential systematic effects impacting calibration accuracy. By integrating planned experimental activities with simulation-driven studies, this work establishes a solid foundation for the development of a robust and well-characterized calibration unit in Phase B.

Accelerometers are devices that sense acceleration and transmit it as an electrical signal to measurement units. Recently, accelerometers have made an important contributionto several fields such as aerospace, space, health monitoring, and other industries.This study is dedicated to the mathematical modelling and development of a newly developed three-axis piezoelectric accelerometer for space applications based on LEO CubeSat missions. The modelling, development, and required simulations are carried out using COMSOL Multiphysics software. The main objective of this work is to develop an easily manufacturable, cost-effective, and sensitive three-axis piezoelectric accelerometer for attitude determination systems in low Earth orbit based space applications.

QUVIK is a Czech-led project of a small UV space telescope that has been selected and funded to be launched in year30/31. Masaryk University will be primarily responsible for developing and running a Science Operation Center that has 2 main tasks: defining most scientifically valuable observation plan (taking into account constraints of Low Earth Orbit and the power budget) and creating the most performing data processing pipeline (with a very limited baseline of on-board data handling). Our experience of operations of small telescopes on ground (mostly run in automatized regime) is the pincipal ingredience in this development. First steps taken in the process closely supervised by ESA support team will be presented.

We show that a Soft X-ray Imager (SXI) onboard the ESA-CAS satellite SMILE will be able to observe various types of mass accreting compact objects in the universe. We show that mainly neutron stars accreting matter from their companions in X-ray binaries are promising targets for evaluating the possibilities of SXI in astronomical research. We present the typical features of the long-term activity of various X-ray binaries in the SXI/SMILE field of view. We also show that binaries with steady-state thermonuclear reactions on board accreting white dwarfs in the Magellanic Clouds are promising targets for SXI observations. We discuss how SXI can contribute to this branch.

This will be the concluding address for the 20th IBWS conference including selected photographs taken during the event. We remind that the IBWS (INTEGRAL/BART) workshops originally focused on the work of High energy astrophysics group (at that dime dominated by young research fellows and students) in Astronomical Institute of the Academy of Sciences of the Czech Republic and relevant national and international collaborators from the field, with intensive student participation. During the early years, these activities were focussed on the ESA INTEGRAL satellite and on the related ground-based robotic telescopes, e.g. the small robotic BART telescope at the Ondrejov Observatory. Nowadays, the IBWS workshops promote regional collaboration in galactic and extragalactic high-energy astrophysics, both experimental as well as theoretical, with an emphasis on the interface between satellite projects and ground-based experiments (e.g. robotic telescopes). At the conference there continued our emphasis on wide participation and presentations of students and young research fellows.

In the operational environment of space missions, the boundary between peak performance and physiological failure may be defined by the efficiency of a single breath. Despite decades of development, respiratory dead space in oxygen masks such as the MBU-20/P oxygen mask could be a critical bottleneck under specific pressure regimes, leading to CO₂ rebreathing and a reduction in cognitive performance. This study addresses these challenges by reformulating classical fluid dynamics into a probabilistic optimization framework. A transient CFD approach is implemented to capture the full complexity of the breathing cycle. A key pillar of the research is the deployment of surrogate modeling via UptimAI, effectively bridging the gap between high-fidelity simulation and time-efficient design optimization within constrained development timelines. This approach enables high-resolution mapping of non-linear gas mixing phenomena and supports the identification of practically relevant design improvements. Preliminary results indicate specific geometric modifications of the mask that significantly enhance flushing efficiency, thereby ensuring a continuous supply of fresh breathing mixture to the pilot.

Cognitive performance determines not only how astronauts and scientists work, but also how well we think, create, and make decisions. Even highly trained individuals experience measurable fluctuations in cognitive performance over time. This contribution presents the ICARUS ARMOR Next Gen experiment, prepared for a future International Space Station mission of Czech astronaut Aleš Svoboda, which aims to predict short-term cognitive performance based on the temporal sequence of monitored stressors. The measurement concept combines cognitive testing, physiological biosignals, and biochemical stress markers into a unified multimodal dataset. These data are used to develop a personalized AI-based surrogate model, conceived as an individual software tool capable of forecasting cognitive performance over the following hours to days. While the experiment is motivated by the extreme conditions of human spaceflight, the approach is directly relevant to everyday personal and professional life. Participants will gain insight into how their own cognitive performance evolves, what factors shape it, and how it may be predicted. Selected tools used for astronaut cognitive testing will be available for hands-on experience, with some already available or becoming accessible for personal use.