Abstract We present the results of unfiltered and $BR$ photometry of SN Ia 2025asm. We determine the decline rate parameter $\Delta m_{15}(B)=1.85$ mag and maximum absolute magnitude $M_B=-18.85$ mag, these data allow to conclude that SN\,2025asm is among the brightest type Ia SNe with high decline rate. We reveal that SN 2025asm does not belong to 1991bg-like SNe, its light and color curve and maximum luminosity show similarity with ``transitional'' type Ia SN iPTF13ebh. The location of SN\,2025asm in a group of galaxies, far beyond the borders of nearby galaxies, indicates that its progenitor belongs to old stellar population.

Gamma-ray bursts (GRBs) are the most luminous electromagnetic explosions in the Universe, and offer unique laboratories for studying relativistic jets, compact-object formation, particle acceleration, and the high-redshift Universe. The early optical emission of GRBs, particularly within seconds to minutes after the burst, carries crucial information about the central engine, jet magnetization, bulk Lorentz factor, and circumburst environment. We present a comprehensive review of the early optical phenomenology of GRBs and the essential role played by ground-based robotic optical telescopes to observe the fleeting early-time phenomena through rapid, automated responses to real-time GRB alerts and high-cadence photometry. We examine the key early optical features of GRBs, including prompt optical emission coincident with the γ-ray phase, bright reverse shock optical flashes, the onset of external forward shock afterglow, and superimposed optical flares, plateaus, and discuss the diagnostic power of each in constraining jet physics. We discuss the physical mechanisms underlying these phenomena and their implications for GRB physics (e.g., estimating the initial Lorentz factor Γ_0, magnetization, and the density profile). Early optical observations have constrained the initial bulk Lorentz factor Γ_0 ∼ 100–1000, weak-to-moderate ejecta magnetization for events with prominent reverse shocks, the circumburst density profile, and the geometry of the magnetic field in the ejecta through polarimetry. We also provide the technical capabilities and landmark contributions of major robotic facilities, and discuss future prospects in the era of SVOM, Einstein Probe, Rubin/LSST, ULTRASAT, TeV observatories, and multi-messenger alerts.

Robotic telescope networks play an important role in capturing early and bright optical afterglows, providing critical insights into the energetics and emission mechanisms of GRBs. In this study, we analyze GRB 230204B, an exceptionally energetic and multipulsed long GRB, detected by the Fermi Gamma-ray Burst Monitor and MAXI detectors, with an isotropic equivalent gamma-ray energy exceeding 10 ^54 erg. Time-resolved spectral analysis reveals a transition in the prompt emission from hard (sub-photospheric-dominated) spectra during early pulses to softer (synchrotron-radiation-dominated) spectra in later pulses, indicative of a hybrid jet composition. We report the discovery and characterization of the optical afterglow using the Mobile Astronomical System of Telescope-Robots (MASTER) and Burst Observer and Optical Transient Exploring System (BOOTES) robotic telescope networks, which enabled rapid follow-up observations starting at ∼1.3 ks post-burst. The optical luminosity at this time was exceptionally high, surpassing that of many other optically bright GRBs, such as GRB 990123 and GRB 080319B. This places the burst among the most luminous optical GRBs observed to date. Long-term radio observations extending to 335 days post-burst were conducted with the Australia Telescope Compact Array. Multiwavelength modeling, incorporating data from MASTER, BOOTES, Devasthal Optical Telescope, Swift/XRT, and radio observations, was conducted using an external interstellar medium (ISM) forward-shock top-hat jet model with afterglowpy . The results reveal a narrow and highly collimated jet with a circumburst density of n _0 ∼ 28.12 cm ^−3 , kinetic energy E _K ∼ 4.18 × 10 ^55 erg, and a relatively low value of ϵ _B = 2.14 × 10 ^−6 , indicating shock-compression of the magnetic field in the surrounding ISM. We constrained a low radiative efficiency of ∼4.3%. This study highlights the indispensable contribution of robotic networks to early afterglow observations and advances our understanding of GRB 230204B unique characteristics and underlying jet physics.

High-energy neutrinos could be produced in the interaction of charged cosmic rays with matter or radiation surrounding astrophysical sources. To look for transient sources associated with neutrino emission, a follow-up program of neutrino alerts has been operating within the ANTARES Collaboration since 2009. This program, named TAToO, has triggered robotic optical telescopes (MASTER, TAROT, ROTSE and the SVOM ground based telescopes) immediately after the detection of any relevant neutrino candidate and scheduled several observations in the weeks following the detection. A subset of ANTARES events with highest probabilities of being of cosmic origin has also been followed by the Swift and the INTEGRAL satellites, the Murchison Widefield Array radio telescope and the H.E.S.S. high-energy gamma-ray telescope. The results of twelve years of observations are reported. No optical counterpart has been significantly associated with an ANTARES candidate neutrino signal during image analysis. Constraints on transient neutrino emission have been set. In September 2015, ANTARES issued a neutrino alert and during the follow-up, a potential transient counterpart was identified by Swift and MASTER. A multi-wavelength follow-up campaign has allowed to identify the nature of this source and has proven its fortuitous association with the neutrino. The return of experience is particularly important for the design of the alert system of KM3NeT, the next generation neutrino telescope in the Mediterranean Sea.

The long gamma-ray burst GRB 191221B has abundant observations in X-ray, optical, and radio bands. In the literature, the observed optical light curve of GRB 191221B displays a plateau around 0.1 d, which is rather peculiar in gamma-ray bursts. Here, we performed detailed analysis of the observational data from Swift/UVOT, Very Large Telescope, and Las Cumbres Observatory, obtained the light curve of the multiband afterglow of GRB 191221B. By examining optical, ultraviolet, X-ray, and radio data for this event, we demonstrate that an on-axis two-component jet model can explain the observations. Our analysis suggests that the narrow component has an initial Lorentz factor of 400 and a jet opening half-angle of 1.4 degrees, while the wide component has an initial Lorentz factor of 25 and a jet opening half-angle of 2.8 degrees. The narrow jet dominates the early decay, whereas the wider jet causes the optical plateau and dominates late decay. According to this model, the reason for the absence of the X-ray plateau is due to the steeper spectral index of the wide component, resulting in a less significant flux contribution from the wide jet in the X-ray bands than in the optical bands. Moreover, we have explained the inconsistency in the decay indices of the UVOT- and Rc-band data around 2000 s using reverse shock emission.

This article presents the early results of synchronous multiwavelength observations of one of the brightest gamma-ray bursts (GRBs) GRB 160625B with the detailed continuous fast optical photometry of its optical counterpart obtained by MASTER and with hard X-ray and gamma-ray emission, obtained by the Lomonosov and Konus-Wind spacecraft. The detailed photometry led us to detect the quasi-periodical emission components in the intrinsic optical emission. As a result of our analysis of synchronous multiwavelength observations, we propose a three-stage collapse scenario for this long and bright GRB. We suggest that quasiperiodic fluctuations may be associated with forced precession of a self-gravitating rapidly rotating superdense body (spinar), whose evolution is determined by a powerful magnetic field. The spinar's mass allows it to collapse into a black hole at the end of evolution.

We present the results of the participation of the MASTER Global Robotic Network in the program to support the aLIGO (O1) and LIGO/Virgo (O2 and O3) gravitational-wave experiments in the electromagnetic channel. This study covers the first observing run O1 from September 2015 to January 2016, the second observing run O2 from November 2016 to August 2017 (only LIGO in January–July, joint LIGO/VIRGO (LVC) in August) and the third observing run O3 from April 2019 to April 2020. The main goal of these observations was to, for the first time in the history of astronomy, perform precise localization of gravitational-wave sources, which successfully resulted in the independent discovery of the kilonova using MASTER telescopes in the process of searching for the source of the GW170817 event. In many other events, dozens of optical transients unrelated to gravitational waves have been detected. Nevertheless, the experience of optical localization of gravitational waves is of exceptional importance for the development of a future successful strategy for the localization of gravitational wave events involving relativistic stars. In addition, objects detected in the analysis of huge areas in the sky, determined by the localization errors of the GW source, have been studied in particular detail by telescopes around the world. Objects such as supernovae, novae, active galactic nuclei, dwarf novae and other explosive phenomena in the Universe have been found and analyzed. More than 220 000 deg2 within the region of the most probable localization of a gravitational wave source have been explored by the MASTER Global Robotic Network. This paper reports on the observations of the MA-STER Global Robotic Network for all alert events from the O1, O2, and O3 observing runs.

We present MASTER Global Robotic Net (Lipunov et al. 2010) earliest optical alert observations of IceCube-170922A error box. We discovered fast variability of blazar TXS 0506+056 27 sec after notice time (73s after the trigger time) at 2017-09-22 20:55:43 UT by MASTER-Tavrida robotic telescope. MASTER found the blazar TXS 0506+056 to be in the off-state after one minute and then switched to the on-state no later than two hours after the event. The effect is observed at a 50-sigma significance level. We also analysed own unique 16-years light curve of blazar TXS 0506+056 (518 data set).

The detailed continuous fast optical photometry analysis obtained by MASTER Global Network for the GRB160625B optical counterpart MASTER OT J203423.51+065508.0 is presented. There are also hard X-ray and gamma-ray emission obtained by the Lomonosov and Konus-Wind spacecrafts detectors. We detected quasiperiodic emission components in the intrinsic optical emission of GRB160625B and propose a three-stage collapse scenario for this long and bright GRB. We associate quasiperiodic fluctuations with forced precession of a Spinar, i.e. self-gravitating rapidly rotating super dense body, whose evolution is determined by a powerful magnetic field. The spinar's mass lead it to collapse into a black hole at the end of an evolution.

Multi-pulsed GRB 190530A, detected by the GBM and LAT onboard Fermi, is the sixth most fluent GBM burst detected so far. This paper presents the timing, spectral, and polarimetric analysis of the prompt emission observed using AstroSat and Fermi to provide insight into the prompt emission radiation mechanisms. The time-integrated spectrum shows conclusive proof of two breaks due to peak energy and a second lower energy break. Time-integrated (55.43 ± 21.30 %) as well as time-resolved polarization measurements, made by the Cadmium Zinc Telluride Imager (CZTI) onboard AstroSat, show a hint of high degree of polarization. The presence of a hint of high degree of polarization and the values of low energy spectral index (αpt) do not run over the synchrotron limit for the first two pulses, supporting the synchrotron origin in an ordered magnetic field. However, during the third pulse, αpt exceeds the synchrotron line of death in few bins, and a thermal signature along with the synchrotron component in the time-resolved spectra is observed. Furthermore, we also report the earliest optical observations constraining afterglow polarization using the MASTER (P < 1.3 %) and the redshift measurement (z= 0.9386) obtained with the 10.4m GTC telescopes. The broadband afterglow can be described with a forward shock model for an ISM-like medium with a wide jet opening angle. We determine a circumburst density of n0 ∼ 7.41, kinetic energy EK ∼ 7.24 ×1054 erg, and radiated γ-ray energy Eγ,iso ∼ 6.05 ×1054 erg, respectively.

This review considers synchronous and follow-up MASTER Global Robotic Net optical observations of high energy astrophysical phenomena such as fast radio bursts (FRB), gamma-ray bursts (including prompt optical emission polarization discovery), gravitational-wave events, detected by LIGO/VIRGO (including GW170817 and independent Kilonova discovery), high energy neutrino sources (including the detection of IC-170922A progenitor) and others. We report on the first large optical monitoring campaign of the closest at that moment radio burster FRB 180916.J0158+65 simultaneously with a radio burst. We obtained synchronous limits on the optical flux of the FRB 180916.J0158+65 and FRB 200428 (soft gamma repeater SGR 1935+2154) (The CHIME/FRB Collaboration, Nature 2020, 587) at 155093 MASTER images with the total exposure time equal to 2,705,058 s, i.e., 31.3 days. It follows from these synchronous limitations that the ratio of the energies released in the optical and radio ranges does not exceed 4 × 105. Our optical monitoring covered a total of 6 weeks. On 28 April 2020, MASTER automatically following up on a Swift alert began to observe the galactic soft gamma repeater SGR 1935+2154 experienced another flare. On the same day, radio telescopes detected a short radio burst FRB 200428 and MASTER-Tavrida telescope determined the best prompt optical limit of FRB/SGR 1935+2154. Our optical limit shows that X-ray and radio emissions are not explained by a single power-law spectrum. In the course of our observations, using special methods, we found a faint extended afterglow in the FRB 180916.J0158+65 direction associated with the extended emission of the host galaxy.

We report on MASTER optical observations of an afterglow-like optical and X-ray transient AT2021lfa/ZTF21aayokph. We detected the initial steady brightening of the transient at 7{\sigma} confidence level. This allowed us to use smooth optical self-similar emission of GRBs model to constrain the explosion time to better than 14 min as well as to estimate its initial Lorentz factor {\Gamma}0 = 20 +/- 10. Taking into consideration the low {\Gamma}0 and non-detection in gamma-rays, we classify this transient as the first failed GRB afterglow.

GRB 190829A at z = 0.0785 is the fourth closest long GRB ever detected by the Neil Gehrels Swift observatory, and the third confirmed case with a very high-energy component. We present our multiwavelength analysis of this rare event, focusing on its early stages of evolution, and including data from Swift, the MASTER global network of optical telescopes, ALMA, and ATCA. We report sensitive limits on the linear polarization of the optical emission, disfavouring models of off-axis jets to explain the delayed afterglow peak. The study of the multiwavelength light curves and broad-band spectra supports a model with at least two emission components: a bright reverse shock emission, visible at early times in the optical and X-rays and, later, in the radio band; and a forward shock component dominating at later times and lower radio frequencies. A combined study of the prompt and afterglow properties shows many similarities with cosmological long GRBs, suggesting that GRB 190829A is an example of classical GRBs in the nearby universe.