Long-duration gamma-ray bursts (GRBs) are powerful cosmic explosions, signaling the death of massive stars. Among them, GRB 221009A is by far the brightest burst ever observed. Because of its enormous energy ( E iso ≈ 10 55 erg) and proximity ( z ≈ 0.15), GRB 221009A is an exceptionally rare event that pushes the limits of our theories. We present multiwavelength observations covering the first 3 months of its afterglow evolution. The x-ray brightness decays as a power law with slope ≈ t −1.66 , which is not consistent with standard predictions for jetted emission. We attribute this behavior to a shallow energy profile of the relativistic jet. A similar trend is observed in other energetic GRBs, suggesting that the most extreme explosions may be powered by structured jets launched by a common central engine.

We present the earliest astronomical observation of a high energy neutrino error box in which its variability was discovered after high-energy neutrinos detection. The one robotic telescope of the MASTER global international network (Lipunov et al. 2010) automatically imaged the error box of the very high-energy neutrino event IceCube-170922A. Observations were carried out in minute after the IceCube-170922A neutrino event was detected by the IceCube observatory at the South Pole. 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. Also we present own unique 16-years light curve of blazar TXS 0506+056 (518 data set).

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 7σ 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 Γ0 = 20 ± 10. Taking into consideration the low Γ0 and non-detection in gamma-rays, we classify this transient as the first failed GRB afterglow.

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We present the results of MASTER Global Robotic Net optical observations of the LIGO GW170104 error-box during the LIGO/Virgo O2 run. We observed 3421 square degrees inside 3σ error-field. Dozens of optical transients unrelated to gravitational waves were discovered as the result of MASTER observation strategy, that we presented, including short very bright MASTER optical transients J133017.28+780951.8.