Igor Evgenevich Molotov

We present the discovery, photometric follow-up, and analysis of the dwarf nova TCP J05415572-2308340, detected during its 2025 superoutburst by the New Milky Way survey. The outburst reached a peak magnitude of 12m.79 in the g-band, with a total amplitude of ~7m.9. Analysis of archival data reveals a previous outburst in 2013, suggesting a supercycle of approximately 12 years.Photometric monitoring over more than 20 days revealed a light curve characteristic of WZ Sge-type dwarf novae, showing an initial decline, a plateau phase, and a sharp drop to quiescence without observed rebrightenings. The superhump period during stage B increased linearly from 0.0547 to 0.0554 days, with a period derivative of Ṗ/P = 5.36±0.2×10^-5, the O-C diagram exhibits a parabolic behaviour expected for a steadily increasing superhump period.Using empirical correlations, we estimate an orbital period of Porb≈0.0540 days. The derived system parameters are: secondary mass Mrd≈0.066M⊙, mass ratio q=0.083, and binary separation a=0.57R⊙. The distance is estimated at ~495 pc from both photogeometric Gaia data and the Patterson absolute magnitude-period relation.The extremely low secondary mass suggests that the donor star may be a brown dwarf, making this system a candidate period bouncer -- a cataclysmic variable that has evolved past the minimum orbital period. The combination of a long superoutburst recurrence time, a large outburst amplitude (7.88 mag in g band), absence of normal outbursts, short orbital period, and probable brown dwarf donor allow us to classify J0541 as a dwarf nova of WZ Sge subclass of SU UMa-type.

The growing density of space objects in low Earth orbit (LEO), driven by the deployment of large satellite constellations, has elevated the risk of orbital collisions and the need for high-precision conjunction analysis. Traditional methods based on Two-Line Element (TLE) data suffer from limited accuracy and insufficient uncertainty modeling. This study proposes a hybrid collision assessment framework that combines Monte Carlo simulation, spline-based refinement of the time of closest approach (TCA), and a multi-stage deterministic refinement process. The methodology begins with probabilistic sampling of TLE uncertainties, followed by a coarse search for TCA using the SGP4 propagator. A cubic spline interpolation then enhances temporal resolution, and a hierarchical multi-stage refinement computes the final TCA and minimum distance with sub-second and sub-kilometer accuracy. The framework was validated using real-world TLE data from over 2600 debris objects and active satellites. Results demonstrated a reduction in average TCA error to 0.081 s and distance estimation error to 0.688 km. The approach is computationally efficient, with average processing times below one minute per conjunction event using standard hardware. Its compatibility with operational space situational awareness (SSA) systems and scalability for high-volume screening make it suitable for integration into real-time space traffic management workflows.

This manuscript presents an approach to accurately determine the orbits of Medium Earth Orbit (MEO) and Geosynchronous Earth Orbit (GEO) space objects by utilizing data from an electro-optical sensor (Optical Satellite Tracking Station (OSTS), Kottamia Observatory station). The proposed method combines an extended and unscented Kalman filter with a semi-analytical propagation model. The effectiveness of this approach is demonstrated through numerical simulations and comparisons with traditional orbit determination techniques. The results drawn from this study show that when comparing both methods, the unscented semi-analytical Kalman filter provided more accurate orbital state estimates and required less time and fewer observations to converge.

Gamma-ray bursts (GRBs) are the most energetic and mysterious events in the Universe, which are observed in all ranges of electromagnetic spectrum. Most valuable results about physics of GRB are obtained by optical observations. GRBs are initially detected in gamma-rays with poor localization accuracy, and an optical counterpart should be found. The faster the counterpart is found, the more it can give to physics. This first phase, as a rule, corresponds to an early afterglow. The next phases of the observations are multicolor photometry, polarimetry, spectroscopy, and few days later the search for a supernova or kilonova associated with the GRB, and finally, observations of the host galaxy. To manage the problem of fast optical observations, telescopes with a small aperture are suitable. They can have a large field of view, which is necessary to cover initial localizations of GRBs. The sensitivity of the telescope+detector may be sufficient to record statistically significant light curve with fine time resolution. We describe one of the networks of telescopes with a small aperture IKI-GRB FuN, and present the results of early optical observation of GRB sources, and discuss the design requirements of the optical observations for effective GRB research in the next decade.

International Scientific Optical Network (ISON) is an open international voluntary project specializing in observations of the near-Earth space objects. Observatories collaborating with ISON provide the global coverage and successfully combine the observations of the space debris and asteroids. The network includes more than 50 telescopes of 27 observatories in 15 countries and has been working since 2005. ISON monitors the whole GEO region and tracks the objects at GEO, GTO, HEO and LEO. ISON data allowing maintenance of the database of the space objects orbits, validating space debris population model and providing conjunction assessment analysis for satellites at high orbits. ISON develops the technology of asteroid survey with small telescopes and arranges regular photometry observations of near-Earth asteroids (NEA) to investigate the YORP effect, search new binary NEAs, and support radar experiments.

We measure the degree of linear polarization of comet 46P/Wirtanen during two months, embracing the perihelion passage in 2018 December with phase angles ranging from α = 18.1° to 46.4°. The polarimetric response P_Q obtained resembles what was previously found in comet C/1975 V1 (West). This suggests 46P/Wirtanen belongs to a group of comets with high maximum positive polarization. In the first half of 2019 February, we conducted BVRI photometry of 46P/Wirtanen and found either neutral or blue colour of its dust, which is in good accordance with measurements of C/1975 V1 (West). While aperture-averaged polarimetry of 46P/Wirtanen reveals a nearly zero polarization P_Q at the lowest phase angle α = 18.1°, simultaneous imaging polarimetry suggests that the negative polarization (P_Q < 0) arises in a region of within 5000 km of the nucleus, where the negative polarization could be as strong as P_Q = −(1.44 ± 0.15) per cent. This observation suggests the existence of the circumnucleus halo and that the coma is populated by at least two types of dust particles. One of those reveals a low positive polarization at side scattering and high negative polarization near backscattering. Both polarimetric features are simultaneously produced by weakly absorbing Mg-rich silicate particles. Another type of dust produces solely positive polarization that could be attributed to carbonaceous particles. This composition of 46P/Wirtanen coma appears to be similar with what was previously found in comet C/1975 V1 (West).

The data on 498 space debris objects with a high area-to-mass ratio (HAMR) detected in 2016–2017 were analyzed to identify possible candidates for the role of "parent objects". As a result, the origin of several HAMR fragments was determined. These fragments separated from three different large objects in the geostationary orbit (GEO) region, including two functioning spacecraft and one rocket launcher stage. Observations of these three objects showed that there were no noticeable differences in their light curves, which indicates the absence of significant changes in the geometric shape, reflective characteristics and motion parameters relative to the center of mass. At least, both spacecraft continued to perform retention maneuvers in their positions on the GEO, and no unpredictable changes were detected in the orbital motion and in the stage light curve. Therefore, the formation of newly discovered fragments cannot be associated with the catastrophic destruction of the “parent objects”.