Sattelite Attitude State Reconstruction

• Andras Szell (AdCoelum Space Research and Consulting LLC)

Spacecraft attitude determination from passive optical observations remains a challenging inverse problem, particularly for resident space objects lacking cooperative sensors or telemetry. This work presents a methodology for reconstructing rotational state information from multi-colour photometric light curves by combining physically based brightness modelling, spectral reflectance effects, and statistical inversion techniques. The approach exploits time-varying brightness measurements acquired in multiple spectral bands to estimate rotational parameters such as spin period and spin-axis orientation while preserving consistency with observation geometry and illumination conditions. A dedicated simulation framework is used to generate synthetic multi-band light curves for controlled validation, enabling quantitative assessment of reconstruction performance under representative observing scenarios. Results demonstrate that multi-colour photometry provides additional constraints beyond monochromatic observations and can improve the observability and interpretability of attitude-related signatures. The presented framework establishes a reproducible foundation for photometric attitude reconstruction and highlights the potential of multi-band optical measurements for future space surveillance and space domain awareness applications.

Tracking LEO satellites with a rolling shutter camera: challenges and solutions

• Radu Gabriel Danescu (Technical University of Cluj-Napoca)

Small objects in the Low Earth Orbit pose unique challenges for tracking, as they are too faint for producing the well-identifiable streaks in images acquired in sidereal tracking mode. The solution is to use the optical instrument in object tracking mode. A particular property of the LEO objects is their high speed, which demands small camera exposure times. Even so, the background stars will be depicted as large streaks, making the astrometric calibration difficult. An even greater challenge is the fact that modern CMOS astronomical cameras use the rolling shutter exposure, each image row being exposed at a different moment in time. This behaviour does not affect sequences acquired with large exposure times (tens of seconds), but becomes critical when the exposure time is comparable with the total frame sweep time. In our case, the sweep time was 250 ms, and the exposure time 200 ms, meaning that the rolling shutter induced motion will be highly visible. Our solution to this problem was to compute a star displacement speed vector, based on the orientation of the streaks in the image, and scale this vector with the time stamp difference relative to the middle image row. By compensating for this displacement, we were able to match the centres of the star streaks with catalog stars and perform astrometric calibration, leading eventually to successful reduction of the LEO sequence.

Multiphysics open source software for spacecraft electromagnetic cleanliness design

• Gabriela Blaga (Astronomical Institute, Romanian Academy, Cluj-Napoca Branch)

The thermoelectric generation of magnetic fields due to temperature gradients in electrically conductive spacecraft materials presents a challenge for missions requiring high-precision magnetic field measurements. A tool is needed at the design phase to model, predict and mitigate these perturbations. Building this tool requires a comprehensive multiphysics approach, combining thermal, electrical, and magnetic modeling, with validation and implementation in mission design workflows. The technical requirements for the software emphasize three key aspects: (1) the need for a sound theoretical understanding of the physical effects, (2) the development of a robust and adaptable simulation tool, and (3) the delivery of user-friendly software that can be seamlessly integrated into ESA’s design and verification processes. This talk presents the progress made along the software development roadmap for ESA contract 4000148213.

The impact of mega-constellations on observational astronomy

• Cristian Omat (Astronomical Institute of the Romanian Academy)

Space Situational Awareness (SSA) has emerged as a critical priority in the modern space era, driven by the rapid growth of satellite deployments into Low Earth Orbit (LEO). While mega-constellations expand global connectivity, they also intensify orbital congestion and amplify operational risks, challenges further compounded by the increasing involvement of commercial actors and a regulatory framework that has yet to fully adapt. The research investigates artificial satellites and space debris in LEO, examining the mega-constellation paradigm and its broader implications for the orbital environment and observational astronomy. To mitigate the impact, a deep learning-based solution was developed for the automatic processing of astronomical images, replacing manual frame selection for scientific analyses. At the global scale, this repetitive, non-standardized process is estimated to generate annual economic losses of 150–180 million euros. Trained on all-sky images from the national MOROI network, the solution is scalable, reconfigurable, and adaptable to individual purposes. The model achieved a precision of 100%, a recall of 91%, and a frame-level accuracy of 95.5%, confirming its readiness for real operational workflows and opening new directions in automated observational data processing. References: [1] C. Omat, M. Birlan, D.A. Nedelcu, S. Anghel (2026). Deep learning approach for automated detection of space objects in astronomical imaging. Astronomy and Computing, vol 55, April 2026. DOI: https://doi.org/10.1016/j.ascom.2026.101081 [2] C. Omat, M. Birlan, D.A. Nedelcu, V. Turcu, F. Deleflie, U.E. Botezatu (2025). Re-entry Survivability Analysis of ERS-2 satellite. Romanian Astronomical Journal,vol 35 (1-2), pag 119-134, DOI: https://doi.org/10.59277/roaj.2025.1-2.07 [3] C. Omat, M. Trelia, M. Birlan, D.A. Nedelcu (2024). Analysis of the re-entry phase of Starlink-1353 satellite. Romanian Astronomical Journal, vol 34, pag 75-91, DOI: https://doi.org/10.59277/RoAJ.2024.1-2.05 [4] C. Omat, M. Birlan, D.A. Nedelcu, S. Anghel (2026). Repurposing all-sky camera systems for satellites and debris detection through deep learning, 5th International Conference on Space Situational Awareness (ICSSA), Tres Cantos - Madrid, Spain, 7-9 April 2026 [5] C. Omat, M. Birlan, D.A. Nedelcu (2025). An automatically approach of space objects detection, 9th European Conference on Space Debris, Bonn, Germany, 1-4 April 2025. ESA Proceedings Database: https://conference.sdo.esoc.esa.int/proceedings/sdc9/paper/264/SDC9-paper264.pdf [6] C. Omat, M. Birlan, D.A. Nedelcu (2025). Real-time Sky Object Detection and Classification using YOLO Algorithm. Prezentare orală la 64th Israel Annual Conference on Aerospace Sciences (IACAS 2025), Haifa, Israel, 20 March 2025. https://www.proceedings.com/79524.html ISBN: 9798331316129

Astronomical Image Processing for Automatic Star Detection and Constellation Visualization

• Ana-Maria Bîzgă (Technical University of Cluj-Napoca)

Abstract — Modern astronomical observations generate large amounts of image data, increasing the need for automated methods capable of detecting and identifying celestial objects. This paper presents a software application designed for the analysis of astronomical images, combining image processing techniques with astronomical reference data. The developed pipeline performs automatic object detection and segmentation, followed by the correlation of the obtained objects with external astronomical information. The application integrates the Astrometry.net service for astrometric calibration, used to establish a correspondence between image coordinates and celestial coordinates through a plate-solving process. Using the obtained calibration parameters, stars from astronomical catalogs are projected onto the image plane and associated with locally detected objects. Furthermore, the proposed pipeline identifies the constellations visible in the analyzed sky region by combining stellar catalog information with constellation structures. The system also provides a visual comparison between locally detected objects and objects identified through astronomical catalogs, facilitating result validation and interpretation. Experimental evaluation on astronomical images demonstrates that the proposed approach successfully combines image processing, astrometric calibration, and constellation visualization, providing an informative representation of the observed sky region. The obtained results highlight the potential of the proposed application as an effective tool for astronomical image analysis. Keywords—astronomical image analysis, Astrometry.net, astrometric calibration, plate-solving, astronomical catalogs, constellation identification

High-Resolution radio imaging of a Compact Symmetric Object

• Zsófia Oltvári (University of Szeged)

The coordinates of the bright radio-loud active galactic nucleus (AGN) J1438+6211 (1437+624) at redshift z=1.094 are known in optical and radio wavebands with sub-milliarcsecond precision. The target shows significant offset, in the order of ~10 milliarcseconds, between its optical and radio positions. I analysed very long baseline interferometry (VLBI) radio images obtained at 5 GHz with the European VLBI Network in 2022 and archival data at multiple frequencies covering more than two decades, to investigate the possible cause of this discrepancy. I found that the radio source is resolved into two major components separated by about 100 milliarcseconds, corresponding to sub-kiloparsec projected linear size. The observed radio structure and the large optical–radio offset suggest that J1438+6211 is a compact symmetric object, a powerful young jetted AGN whose radio emission originates from hotspots where the jet interacts with the surrounding interstellar medium.

Planetary dynamics in hyperbolic non-Euclidian geometries

• Tiberiu Harko (Babes-Bolyai University)

We consider the implications of the extension's of Newton's law of gravitation as proposed in the framework of the Bolyai-Lobachevski hyperbolic geometry. In particular, we focus on the negatively-curved hyperbolic space, $H^3$, and we investigate the generalisations of Newton's inverse-square law of the gravitational force in this geometry, its properties, and its physical implications. We obtain the solutions of the two-body problem in the non-Euclidian hyperbolic Newtonian gravity by considering that the absolute space of Newton is of the Bolyai-Lobachevski type. The equations of the planetary orbits, as well as the generalization of Kepler's third law are derived. The perturbations of the orbits are also analyzed, and the expression of the perihelion precession of the planets is obtained.

Kinetic Schwinger pair production in the bare strange-star electrosphere

• Tania Flavia Ciceo (Babeș-Bolyai University, Faculty of Physics)

A bare strange star is bounded by a thin electron layer, the electrosphere, whose overcritical field produces electron–positron pairs through the Schwinger mechanism. We re-examine this by integrating the relativistic Vlasov–Maxwell system, with a Schwinger pair-production source and the full two-current field equation, on a finite-temperature electrosphere background. We show that the surface pair-creation rate is governed by how well the sharp Fermi edge in the Pauli-blocking factor is resolved. The rate converges to the Usov value, about $2\times10^{53}\,\mathrm{s^{-1}}$ at $T=3\,m_{\mathrm{e}}$. The surface field is not enhanced, the kinetic field follows the electrostatic solution where pairs form. Including relaxation-time collisions reduces the pair luminosity by a few percent.

Feature-Enhancing Pipeline for Faint Satellite Streak Detection using YOLOv8

• Cristian Croitoru (Technical University of Cluj Napoca)

Detecting faint, linear satellite streaks in astronomical images is challenging due to high sensor dynamic range, stellar clutter, and atmospheric noise. Standard global normalization techniques often cause information loss by drowning these weak features in the background noise. To compensate for this, we propose a feature engineering pipeline that transforms raw FITS data into a three-channel composite image. The pipeline integrates multi-percentile contrast optimization to handle high dynamic range, a 2D Gabor filter bank to extract linear features across multiple orientations and spatial frequencies, and Contrast Limited Adaptive Histogram Equalization (CLAHE) for enhanced local contrast and noise suppression. These engineered channels directly feed geometric and intensity priors into a YOLOv8 object detection network, yielding consistent results throughout different confidence thresholds.

Observations of T Coronae Borealis During and After the Recent Pre-Eruption Dip

• Cristian Danescu (Astronomical Institute of Romanian Academy)

T Coronae Borealis is a recurrent nova system that erupts approximately every 80 years. Given that the last outburst occurred in 1946 and recent unusual activity, including a "pre-eruption dip" similar to that seen before the previous event, a new eruption is thought to be imminent, sparking intense interest. We present recent photometry and spectroscopy covering this dip and the subsequent recovery. While the optical spectrum typically displays a hot continuum from the white dwarf and accretion disk alongside a red giant secondary, we found that the hot component vanished during the dip. It has since recovered, showing high levels of activity. This ongoing observational campaign of T CrB involves observers from all over the world and will provide the most comprehensive coverage of a nova system leading up to an eruption.

Discovery and comprehensive analysis of the most compact 3+1-type quadruple stellar system, TIC 120362137, containing a triply eclipsing triple subsystem and a just evolved primary star

• Tamás Borkovits (Baja Astronomical Observatory of Szeged University & HUN-REN-SZTE Stellar Research Group)

Hierarchical multiple stellar systems with short outer periods comprise an important subgroup of multiple star systems. In this paper we present the discovery and spectro-photodynamical analysis of the most compact known 3+1 quadruple stellar system, TIC 120362137. Through investigations of the observations made with the TESS satellite and ground-based follow up measurements, we find that the system consists of an eclipsing binary with a few-day-period that in turn eclipses, and is eclipsed by, a third star on a $P_\mathrm{mid}=51.3$ d orbit. This inner subsystem, which contains three stars that are more massive and hotter than the Sun, is more spatially compact than Mercury's orbit around our Sun, and is orbited by a fourth Sun-like star with a period $P_{\rm out}=1046$ d. We detect the spectral lines of all four stars, making this system the most thoroughly studied 3+1 type quadruple stellar system. The future evolution of TIC 120362137 is also modelled, and we conclude that this entire system will likely end up as a pair of white dwarfs.

Analysis of the solar active region NOAA 14366

• Cristian Danescu (Astronomical Institute of Romanian Academy)

In this study, we analyzed the structural and magnetic evolution of the active region NOAA 14366, using the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO). The region was visible on the solar disk between January 31 and February 11, 2026. Characterized by an compact β-γ-δ magnetic configuration, it has produced a large number of major solar flares (6 X-class and 66 M-class solar flares), which places it in third place among the most productive active regions, in terms of flares, in the last five decades. We focused our investigation on the X8.1-class solar flare that occurred on February 1, 2026. To understand its three-dimensional coronal magnetic topology, we reconstructed the coronal magnetic field using Valori's nonlinear force-free field magnetofrictional extrapolation (NLFFF) method. Finally, we compared the resulting three-dimensional coronal magnetic field, derived from photospheric observations, with coronal imaging data to assess the consistency of the reconstructed magnetic structure.

Noise Idealization Effects on Null Stream Tests for Non-Tensorial Gravitational Wave Polarizations

• Balázs Cirok (University of Szeged)

The expanding catalog of gravitational wave detections enables novel tests of General Relativity, including probes of waveform polarization content. Many polarization studies rely on null stream methods, neglecting the known non-stationary and non-Gaussian features of detector noise. Using simulations, we quantify how this noise idealization affects inferences of non‑tensorial polarization modes and characterize the resulting bias in null stream polarization tests.

Searching for Supermassive Black Hole Binaries via Pulsar Timing Arrays

• Richárd Tamás Varga (University of Szeged)

We analyzed supermassive black hole binary (SMBHB) candidate systems whose parameters were constrained by electromagnetic surveys. We extracted data from the following catalogs: the Catalina Real-Time Transient Survey (CRTS), the Palomar Transient Factory (PTF), Pan-STARRS, and the Zwicky Transient Facility (ZTF). Based on these data, we estimated the characteristic strain and frequency of the gravitational waves (GWs) emitted by the investigated sources. We plotted the results and compared them with the sensitivity of current pulsar timing arrays (PTAs) based on surveys by the International Pulsar Timing Array (IPTA) and the North American Nanohertz Observatory for Gravitational Waves (NANOGrav). We found that it is currently not possible to detect GWs from these SMBHB candidates using existing techniques. However, we examined the parameters on which the sensitivity curve depends, and how future sensitivity could be improved with the planned Square Kilometre Array (SKA). We conclude that besides the 3C 66B and OJ 287 systems, there could be GWs from other SMBHB candidates which may become observable with advanced PTAs.

Early Dark Energy constraints from Nucleosynthesis

• Teodora Matei (Babes-Bolyai University, Cluj-Napoca)

In recent years, the $\Lambda$CDM model has proven insufficient to fully explain the mysteries of our Universe. The emergence of a dark energy component in the early Universe has motivated a variety of frameworks aimed at closing the gap between early and late-time cosmological observations. Early Dark Energy models may alleviate existing tensions by proposing varying equations of state that alter nuclear reaction rates during the nucleosynthesis era, therefore constraining the maximum model parameters past which the standard BBN results can no longer be recovered. We investigate four such models, a cosmological constant, linear and polytropic dynamical equations of state, and a temperature-dependent formulation, and by comparing their predictions against standard BBN observables through a numerical pipeline, we identify the maximally allowed dark energy density for each case.

On the signature of the interplay between periodicity, quasi-periodicity, and data sampling on the exoplanet detection in radial velocity data

• Alexandru Pop (Astronomical Institute of the Romanian Academy, Astronomical Observatory Cluj-Napoca)

The detection of exoplanets using radial velocity (RV) data frequently proved to be a difficult task. It requires the disentangling the periodic planetary signal(s) and the quasi-periodic stellar signal which often is the dominant one. An interesting situation inspired by our recent reanalysis of the RV data on TOI-837 is illustrated using synthetic data. The planetary signal is modeled by a periodic harmonic component, while the quasi-periodic signal is simulated using an adequate discrete second-order autoregressive process. The effect of the data sampling is displayed using both evenly and unevenly spaced data. In the latter situation, the well-known technique of sequential pre-whitening was able to unveil the spectral signatures of both quasi-periodic and periodic components of the synthetic signal. We emphasized that the identification of the symmetrical structure(s) of peaks induced by the spectral window requires the representation of the amplitude/power spectrum versus frequency, in accordance with the definition of the Fourier transform, not versus period.

Separating periodic and quasi-periodic signals from noisy, irregularly sampled time series

• Maria Craciun (Tiberiu Popoviciu Institute of Numerical Analysis, Romanian Academy)

Separating periodic, quasi-periodic, and stochastic signals out of noisy, irregularly sampled time series is a central problem of time-domain astronomy. It is of particular interest in the problem of extra solar planets. In the analysis of observational data the three regimes are easily confused once time gaps and colored noise distort their spectra. This talk focuses on the quasi-periodic case modelled as a second-order autoregressive process. We approach the component separation as a problem of generative modelling and parameter estimation, and compare two complementary approaches: Gaussian-process regression with a damped-oscillator kernel, and a state-space/Kalman-filter formulation — both of which accommodate gaps and uneven sampling natively. Using synthetic time series with controlled period, coherence, noise level, and cadence (both evenly and unevenly spaced), we assess the accuracy and bias of the recovered parameters and the calibration of the inferred uncertainties.

Photometric survey of 47 Near-Earth Asteroids within NEOPOPS

• Sorin Ion (Observatoire de Paris)

We present the partial results of a study conducted within the NEOPOPS project [1], the taxonomic classification [2] of 47 near-Earth asteroids (NEAs) through a probabilistic clustering method developed by Max Mahlke and collaborators [3]. Broadband photometry B, V, R, and I of several NEAs obtained during 2025–2026 with the 1.2 m telescope at Observatoire de Haute Provence (France) was used. Data reduction and instrumental magnitudes were computed using Tycho Tracker software [4]. After applying statistical cleaning and sigma-clipping methods, we derived color indices and converted them into spectral reflectance which was used for the taxonomic classification. From 55 observed objects, we classified 47 asteroids (85.5%), 25 objects belonging to the S-complex (including Q class and O class), 12 to the C-complex (including B class), 4 to the M-complex, and 6 to the V-type. The classification quality is good (72.3%) and moderate (23.4%), only 2 objects having ambiguous classification. Within the 47 NEAs, we analysed 27 Potentially Hazardous Asteroids (PHAs), S-complex being assigned to 14 PHAs, C-complex to 7 objects, 2 to M-complex, and 4 to V-type asteroids. Multi-band photometry provides an accessible and faster way to estimate surface composition and therefore is essential in understanding the evolution of our Solar System and in elaborating plans to prevent, reduce or manage the consequences of a potential impact of a NEA with Earth which represents one of the most threatening natural hazards to our planet. References 1. Ieva, S. EPSC-DPS Joint Meeting 2025 2. Birlan M., Barucci, A., Belskaya, I., et al Astronomy & Astrophysics, Volume 689, id.A334, 12 pp 3. Mahlke, M., Carry, B., Mattei, P.-A., Astronomy & Astrophysics, Volume 665, id.A26, 32 pp 4. Parrott, D. (2023). Tycho Tracker User Guide (v13): Photometry and Astrometry Software Documentation. [Software manual]

Weak gravitational lensing in Einstein—Born—Infeld black hole spacetimes

• Tegze Tordai (Department of Theoretical Physics, University of Szeged, Hungary)

Modelling light-signals as shockwaves - that is, discontinuities in the first derivative of the Faraday-tensor - propagating through space-time results in a light cone condition defining the characteristic hypersurfaces of propagation. In non-linear electrodynamics, these can be given as null cones of an effective metric generally differing from the background metric representing gravity. Born—Infeld electrodynamics stands out as a non-linear theory without vacuum birefringence, allowing for only one such light cone. A known perturbative solution of the Einstein—Maxwell system is sufficient to integrate the null geodesics of the effective metric in Einstein—Born—Infeld theory along the equator of a compact object with electric and magnetic field to obtain the deflection angle up to first order. Substituting this into the exact lens equation results in a first order lensing polynomial, which is explored generally with focus on the interdependence of observable quantities on the ratio of magnifications and image positions, giving information about the parameters of the lensing object. Results are provided for known subcases and some mistakes in the literature are corrected.

The Observability of Gravitational Waves in Scalar-Tensor Theories

• Kata Karácsonyi (University of Szeged)

The observation of gravitational waves has opened new possibilities for testing theories of gravity. In scalar–tensor theories, additional breathing and longitudinal scalar polarizations are predicted alongside the plus and cross tensor modes. Scalar gravitational radiation appears one post-Newtonian order earlier than the quadrupolar tensor radiation, allowing the scalar polarization to be decomposed into quadrupolar and dipolar contributions. The observability of polarization modes depends on the gravitational-wave detector network, the intrinsic parameters of the compact binary system, and the inclination of the source. By implementing the frequency-domain waveform model of Ref. [1] in a Python code, I investigate how the optimal signal-to-noise ratio of the purely tensor and scalar-tensor gravitational-wave signals varies with the inclination angle of the source. Furthermore, by extending the waveform model of Ref. [2] with scalar polarizations, we demonstrate through spectrogram and Q-transform representations that the dipolar scalar polarization evolves at half the frequency of the quadrupolar tensor and scalar polarizations. The dipolar scalar polarization becomes visibly distinguishable from the quadrupolar scalar contribution and the quadrupolar polarizations predicted by general relativity at sufficiently low frequencies. My results indicate that the presence of scalar polarizations produces observable deviations in gravitational-wave signals in the low-frequency regime inaccessible to current LIGO–Virgo detectors, for suitable detector sensitivities and for sufficiently inclined systems (more than about 40◦). Through detailed simulations of gravitational-wave signals, I prove that although the quadrupolar tensor radiation is always dominant across inclinations, the presence of scalar polarizations raises the optimal signal-to-noise ratio near edge-on inclinations, potentially bringing it above the minimum threshold for observability. By visualizations of simulated low frequency gravitational-wave signals, we show that the dipolar scalar polarization appears as a distinct feature separated from the quadrupolar polarizations on spectrogram and Q-transform representations. These results reveal a potential new method for testing general relativity with the third-generation Einstein Telescope gravitational-wave observatory currently under development in Europe. [1] H. Imafuku, H. Takeda, A. Nishizawa, D. Watarai and K. Cannon, *Statistical biases in parametrized searches for gravitational-wave polarizations*, Phys. Rev. D **112** (2025), 024028. [2] C. Cutler, É. E. Flanagan, *Gravitational waves from merging compact binaries: How accurately can one extract the binary’s parameters from the inspiral waveform?*, Phys. Rev. D **49** (1994), 2658.

Fluid interpretations of the scalar field in kinetic gravity braiding

• László Árpád Gergely (HUN-REN Wigner RCP)

Gravity theories in which the metric tensor is complemented by a minimally coupled kinetic gravity braiding type scalar field obey all present observational constraints. The k-essence part of the scalar field is either equivalent to a perfect fluid (when the scalar gradient is timelike), an inhomogeneous type I fluid with tangential pressures equal to minus its energy density (for spacelike gradient) or a type II fluid with radial heat flow (for null gradient). We show that the energy-momentum tensors of generic k-essence scalars with temporal and spatial gradients differ by a crossflow of radiation streams. The energy conditions require that a k-essence with null gradient should degenerate into null dust. Then we carry out a similar analysis for the much more complicated proper kinetic gravity braiding scalar field. By casting its energy-momentum tensor into a 2+1+1 form, we recover many of the features identified for k-essence. In particular, the proper kinetic gravity braiding scalar with null gradient appears as null dust. In the case of temporal and spatial gradients, beyond the type of terms already present for k-essence, the fluid decomposition of the energy-momentum tensor of proper kinetic gravity braiding scalars acquire additional heat transport and pressure anisotropy contributions, scaling with the two normal fundamental scalars and the 2-accelerations of the normals entering the decomposition.

Dark Energy and Cosmological Bounce Supported by an Unconventional Spinor Field

• Zoltán Keresztes (University of Szeged, Hungary)

We introduce a model which generalizes the Einstein–Cartan–Dirac theory, including local phase invariance of the spinor field supported by a gauge scalar field and certain couplings to the torsion. A natural gauge choice reduces the field equations to that of the Einstein–Dirac theory with a Dirac field potential that has polar and axial spinor currents. We identify a new potential term proportional to the square of the ratio of Dirac scalar and axial scalar, which provides a dark energy contribution dominating in the late-time Universe. In addition, the presence of spinor currents in the potential may induce the bounce of a contracting universe.

Hamiltonian formalism for the Rarita–Schwinger system

• Bence Juhász

We extend our previous investigation of the canonical description of Dirac and Schrödinger systems for the massive Rarita–Schwinger system, the vector-valued spinor theory describing spin-3/2 fields. We simplify the Lagrangian and Hamiltonian descriptions by introducing a modified time derivative. We discuss both the simplest and the Hermitian Lagrangians, which differ by a total divergence. Through highly intuitive methods, we identify two new Hamiltonians, both of them correctly reproducing all aspects of the dynamics. In the more systematic approach of the Dirac–Bergmann framework, we analyze the massive Rarita–Schwinger system, finding that it exhibits a more complex constraint structure, which requires a careful analysis. We introduce a properly factor ordered Poisson bracket adapted to the spinorial structure. The time evolution of the constraints reproduces the Rarita–Schwinger equations, while also fixing all generalized velocities. The 6 second class constraints require the introduction of a sound Dirac bracket, equally adapted to the spinorial structure. The 2 first class constraints represent auxiliary degrees of freedom, which do not generate gauge transformations. Thus, the massive Rarita–Schwinger system provides a physically relevant counterexample to the Dirac conjecture. Finally, we identify reduced phase space coordinates in which the Dirac bracket reduces to a Poisson bracket, and we formulate a quantization rule based on this structure. These results provide a consistent Hamiltonian and quantization framework for the massive Rarita–Schwinger system.

Is the $\Lambda$CDM in Crisis ? Evidence of Dynamical Dark Energy and Progenitor Age Bias in Supernova Cosmology

• Himanshu Chaudhary (Universitatea Babeș-Bolyai din Cluj-Napoca)

The $\Lambda$CDM model has long been regarded as the standard paradigm of modern cosmology, providing an excellent description of the Universe across a wide range of observations, from the cosmic microwave background to large-scale structure formation and Type Ia supernovae. The discovery of the accelerated expansion of the Universe further established dark energy as one of the central components of the cosmological model. In this talk, I will show that the preference for a dynamical dark energy model over $\Lambda$CDM ranges from $2.0\sigma+$-$3.0\sigma+$, depending on which SNe Ia sample is combined with DESI DR2 and CMB observations. Interestingly, we find that the dark energy behavior preferred by DESI DR2 is characterized by the \textbf{Quintom-B} behavior ($w_0 > -1$, $w_a < 0$, and $w_0 + w_a < -1$). I will further discuss the implications of the \textbf{Project YONSEI} results, which provide evidence for luminosity evolution in Type Ia supernovae associated with progenitor age effects and host galaxy properties. We incorporate progenitor age-bias corrections into cosmological analyses and investigate their impact on dark energy constraints. Remarkably, after applying the age-bias correction, the dynamical dark energy model over $\Lambda$CDM ranges from $7\sigma+$--$11\sigma+$. I will also present evidence for phantom crossing behavior. Furthermore, I will discuss how the peak of the posterior distribution for $\sum m_{\nu}$ shifts toward the normal mass ordering when using the DESI DR2 + CMB + Union3 combination after applying the corrections. Finally, I will discuss the evidence for a non-accelerating Universe scenario after applying the age-bias correction, and show that the $H_0$ tension in dark after age-bias correction.

A Technical Assessment of Lunar Occultation of SgrA* via Sequential 21cm On-The-Fly Radio Mapping in Hong Kong

• C.S. Leung (Hong Kong Astronomical Society)

In this paper, we presents a technical assessment of an observational event capturing the lunar occultation of Sgr A* on 12th of March 2026, by using the Italian Primalucelab SPIDER 300A radio telescope in Hong Kong. Within the four hours observation window, a 2D On-The-Fly (OTF) mapping technique was sequentially applied to generate a time series of 12 radio images at the 21cm wavelength. The raw spatial data revealed a continuous 3% to 4% increase in global intensity across the sequential maps rather than a distinct focal dip, indicating a strong instrumental thermal drift and atmospheric background variation over the extended scanning period. We analyze the limitations of small aperture radio mapping under intense urban radio frequency interference (RFI) and outline a future image processing pipeline. That is the specifically background subtraction and relative radio photometry. It will be the basic requirements to extract faint transient signals from drifting baselines in urban radio astronomy.

Multi-station simultaneous observations of artificial satellites

• Andreea-Catalina Pop (University of Bucharest - Doctoral School of Physics)

This paper presents preliminary results obtained from simultaneous optical observations of the geostationary object Jam E Jam using the Berthelot and SkEYE telescopes located in Romania. The experimental campaign validated the feasibility of dual-station astrometric observations and demonstrated the potential of distributed optical systems for monitoring Resident Space Objects (RSOs) in the context of Space Situational Awareness (SSA). The analysis identified time-base inconsistency as the dominant source of measurement error. While the Berthelot system underwent repeated calibration campaigns in the last six years and has a known time-bias with no significant drift, no such campaign was performed for SkEYE. The lack of this data is affecting the accuracy of quasi-simultaneous measurements. To mitigate these limitations, calibration procedures based on simultaneous observations of Galileo navigation satellites are currently being implemented in order to improve timing stability and astrometric precision. This paper presents the observational setup, synchronization challenges, calibration methodology, and preliminary astrometric results. In addition, visibility simulations for two supplementary optical sensors are presented in order to evaluate the potential benefits of a distributed multi-station optical architecture for RSOs observation in MEO, HEO, and GEO regimes.

Exo4Edu Romania: Preliminary results and lesson learned

• Iharka Csillik (Romanian Academy. Astronomical Institute. Cluj-Napoca Astronomical Observatory)

Abstract: The Exo4Edu Romania initiative is a component of the Exo4Edu Erasmus+ project[1,2], collaborating with three additional countries: France, Portugal, and Albania. The project is leaded by Paris Observatory, France. The project provides easily comprehensible information regarding exoplanets and the search for extraterrestrial life in the Universe, also available in the Romanian language. Simultaneously, there is a focus on enhancing skills in STEAM subjects. The initiative created a toolkit featuring a revised database of exoplanets, along with resources and activities in Romanian, enabling educators to instruct their students more effectively in their own language. Furthermore, to fulfill the primary objective, researchers from the Romanian Academy organized a nationwide training initiative aimed at providing teachers with high-quality, innovative courses[3] and activities[4] to implement in their educational institutions. Consequently, similar to a massive avalanche, by training 21 teachers, we were able to reach and educate a greater number of children in their respective schools. References: [1] - Mirel Birlan, Ana Naghi, Sorin Marin, Carmen Busu, Iharka Szücs-Csillik, Alain Doressoundiram, Gustavo Rojas, Mimoza Hafizi, Francoise Roques - *Învățarea astronomiei prin intermediul modulului educațional al exoplanetelor* – Astro-Space-Fest 2025 Targoviste 16-17 octombrie 2025 [2] - Mirel Birlan, Alain Doressoundiram, Sorin Marin, Diana Ionescu, Florent Deleflie, Alin Nedelcu - *L'astronomie comme vecteur pour les sciences exactes dans l'éducation formelle* - 2eme Symposium francophone de la Recherche scientifique, Bucharest, Roumanie, 27-28 novembre 2023. [3] – Iharka Szücs-Csillik - *Education case studies for Quality Education in Astronomy* – Romanian Astronomical Journal 32 (1), p. 159–176, 2022. [4] - Iharka Szücs-Csillik – *How long would it take to reach your chosen exoplanets?* and *How do you imagine an exoplanet?* - https://scholar.exoplanet.eu/ portal: *To do in Class/Educational activities*.

Strategy for Astronomy Literacy in Romania

• Dana Ficut-Vicas (Astronomical Observatory Cluj-Napoca, Romanian Academy Cluj Branch)

In the context of Romania joining the OCDE is of outmost importance to consider aligning the educational knowledge content with the literacy standards worldwide in all disciplines including astronomy. At the international level the astronomy literacy standards have been defined by Russo et. al. 2019 and within the IAU Astronomy Education Office assessment instruments of astronomy concept inventories are being developed. In Romania, the status of astronomy as a science suffers from a duality beyond compare, while it is a subject of research it is not a subject of study in the national curricula. As a consequence, the access to astronomy education is inadequate and creates severe inequalities among students. We propose to overcome the disadvantages of our Romanian reality with a strategy that transforms isolated astronomy outreach events in bricks that build a complete and structured knowledge in astronomy ensuring astronomy literacy at all levels of our society. Our research looks at astronomy education over time in Romania since the beginning of the nineteenth century making comparison with the themes of astronomy literacy today. Apart form the formal astronomy education we also look into the non-formal approaches to astronomy education publicly available and assess how well the astronomy literacy standard is being covered and propose a strategy to maximise the impact of all astronomy education resources available for Romania in order to achieve high quality and equitable astronomy education for Romanians.

Assessing the observational infrastructure and strategic roadmap of the Astronomical Institute of the Romanian Academy

• Mirel Birlan (Astronomical Institute of the Romanian Academy)

Mirel Birlan1, Alin Nedelcu1, Vlad Turcu1,2, Adrian Sonka1, Octavian Blagoi1, Simon Anghel1, Madalina Trelia1,3, Cristian Omat1, Octavian Badescu1, Petre Paraschiv1, Catalina Pop3,4, Dan Moldovan2, Diana Ionescu1, Cristian Danescu1, Nicu Dociu1, Liviu Ghergu1 1 Astronomical Institute of the Romanian Academy 2 Cluj Napoca Astronomical Observatory 3 Ministry of Defense, Space and Radiocommunication Agency 4 University of Bucharest, Faculty of Physics As the main institution for astronomical research in Romania, the Astronomical Institute of the Romanian Academy (AIRA) manages a distributed network of observational facilities located in Bucharest, Cluj-Napoca, and Timișoara. During the last decade, the strategic roadmap for the observational astronomy was based on the renewal of groundbased instrumentation (telescopes, refractors, radio receivers) in the context of new strategy of topics based mainly on emergent scientific domains such as planetary defense, space surveillance and tracking (SST), solar activity monitoring, and stellar dynamics [1, 2, 3, 4]. By equipping observational assets with cutting-edge digital sensors (CCD, sCMOS) the institute successfully bridges traditional astrometry with contemporary astronomy and space science demands. AIRA is undergoing a strategic modernization process aimed at integrating its facilities into global and European research networks (such as the activities related to the European Space Agency, ground-based tracking networks[5], and international observational campaigns). Future plans focus on upgrading existing optical systems to fully automated and robotic capabilities, enhancing data processing pipelines through artificial intelligence, and expanding the infrastructure to mitigate light pollution challenges. Additionally, emphasis is placed on participating in space situational awareness (SSA) and space surveillance and tracking (SST) programs and developing new observational stations equipped with wider-field instruments. The presentation will give an overview of key activities related to the infrastructure and the new perspectives opened to the development of it. References: [1] Trelia, M. Nedelcu, D.A., Birlan, M. - APSIS: Automated Photometric Survey of Inactive Satellites for rotational dynamics and lightcurve characterization, Acta Astronautica, Volume 242, pp. 85-106, 2026 [3] Birlan, M.; Sonka, A.; Badescu, O. and 10 more authors- Berthelot, the new astronomical station in Romania – Romanian Astronomical J., Vol. 31, No. 1, p. 41-56 [3] Birlan, M., Plesca, V., Gandescu, C.H., Nedelcu A., Balan M., Banica C.K., Pandele C, Sonka A., Georgescu T. - Observational asset for Near-Earth Objects, artificial satellites, and space debris: an assessment of concept, Rom Astron. J., vol 28, n.2, pp 69-80, 2018; [4]Omat, C., Birlan, M., , Nedelcu, A., Turcu, V., Deleflie, F., Botezatu, U. – Re-entry survivability analysis of ERS-2 Satellite - Romanian Astronomical J., vol 35 no 1-2, 2025