This paper considers latest highlights in simultaneous and follow-up optical observations of high energy astrophysical phenomena by MASTER Global Robotic Net. Such extreme Universe sources includes ...gamma-ray bursts, gravitational wave events, detected by LIGO/Virgo, fast radio bursts, high energy neutrino sources and others. Some of the neutrinos detected by ground-based facilities owe their births to supermassive black holes – blazars, which are in a special anxious state with high statistical reliability. We discovered the effect of a rapid decrease in the brightness of the blazar PKS 0735+17 at the time of the multiple detection of the high-energy neutrino event IceCube-211208A. This decrease in brightness within several hours was detected with a high confidence (SNR 10) in comparison with a multi-day brightening state of the blazar, which was accompanied not only by a maximum increase in the average brightness, but also by an increase in the amplitude of its brightness fluctuations. Additionally, we analyzed all cases of successful observation of blazars around neutrino events and obtained statistically reliable indications of the relationship between neutrino events and optical activity of blazars in the doubled error box at the 4.2
level.
Aims.
We investigate the long gamma-ray burst (GRB) 140629A through multiwavelength observations to derive the properties of the dominant jet and its host galaxy.
Methods.
The afterglow and host ...galaxy observations were taken in the optical (
Swift
/UVOT and various facilities worldwide), infrared (
Spitzer
), and X-rays (
Swift
/XRT) between 40 s and 3 yr after the burst trigger.
Results.
Polarisation observations by the MASTER telescope indicate that this burst is weakly polarised. The optical spectrum contains absorption features, from which we confirm the redshift of the GRB as originating at
z
= 2.276 ± 0.001. We performed spectral fitting of the X-rays to optical afterglow data and find there is no strong spectral evolution. We determine the hydrogen column density
N
H
to be 7.2 × 10
21
cm
−2
along the line of sight. The afterglow in this burst can be explained by a blast wave jet with a long-lasting central engine expanding into a uniform medium in the slow cooling regime. At the end of energy injection, a normal decay phase is observed in both the optical and X-ray bands. An achromatic jet break is also found in the afterglow light curves ∼0.4 d after trigger. We fit the multiwavelength data simultaneously with a model based on a numerical simulation and find that the observations can be explained by a narrow uniform jet in a dense environment with an opening angle of 6.7° viewed 3.8° off-axis, which released a total energy of 1.4 × 10
54
erg. Using the redshift and opening angle, we find GRB 140629A follows both the Ghirlanda and Amati relations. From the peak time of the light curve, identified as the onset of the forward shock (181s after trigger), the initial Lorentz factor (Γ
0
) is constrained in the range 82–118. Fitting the host galaxy photometry, we find the host to be a low mass, star-forming galaxy with a star formation rate of log (SFR) 1.1
+0.9
−0.4
M
⊙
yr
−1
. We obtain a value of the neutral hydrogen density by fitting the optical spectrum, log
N
HI
= 21.0 ± 0.3, classifying this host as a damped Lyman-alpha. High ionisation lines (N
V
, Si
IV
) are also detected in the spectrum.
The Tunka Radio Extension (Tunka-Rex) is a digital antenna array, which measures radio emission of the cosmic-ray air-showers in the frequency band of 30-80 MHz. Tunka-Rex is co-located with the ...TAIGA experiment in Siberia and consists of 63 antennas, 57 of them are in a densely instrumented area of about 1 km
2
. In the present workwe discuss the improvements of the signal reconstruction applied for Tunka-Rex. At the first stage we implemented matched filtering using averaged signals as template. The simulation study has shown that matched filtering allows one to decrease the threshold of signal detection and increase its purity. However, the maximum performanceof matched filtering is achievable only in case of white noise, while in reality the noise is not fully random due to different reasons. To recognize hidden features of the noise and treat them, we decided to use convolutional neural network with autoencoder architecture. Taking the recorded trace as an input, the autoencoder returns denoised traces, i.e. removes all signal-unrelated amplitudes. We present the comparison between the standard method of signal reconstruction, matched filtering and the autoencoder, and discuss the prospects of application of neural networks for lowering the threshold of digital antenna arrays for cosmic-ray detection.
The concept of a multi-functional astronomical complex as applied to robotic astronomy networks and systems is formulated. The practical realization of this concept in the MASTER global network of ...robotic telescopes of Moscow State University is described. The dynamically integrated MASTER database, which transforms a network of robotic telescopes into a robotic network, is described. Real, multi-channel astronomical observations obtained on the MASTER global network are used to show the effective application of this concept. The MASTER global network is continuously participating in multi-wavelength and multi-channel observations aimed at studying astrophysical sources located in extreme conditions, including the sources of gravitational waves registered by the LIGO/VIRGO detectors, of high-energy neutrinos detected by IceCube and ANTARES, and of fast radio bursts (FRBs) and gamma-ray bursts (GRBs). The MASTER network provided the most extensive survey of the first error field for the LIGO gravitational-wave outburst GW 150914 (5000 square degrees) and carried out the first independent localization of the gravitational-wave event GW170817. TheMASTER network has also discovered more than 1600 optical transients with various physical natures. Data obtained with the MASTER network have been used to provide pointing information to major ground-based and space-based telescopes.
We report the early discovery of the optical afterglow of gamma-ray burst (GRB) 140801A in the 137 deg... 3-... error-box of the Fermi Gamma-ray Burst Monitor (GBM). MASTER is the only observatory ...that automatically reacts to all Fermi alerts. GRB 140801A is one of the few GRBs whose optical counterpart was discovered solely from its GBM localization. The optical afterglow of GRB 140801A was found by MASTER Global Robotic Net 53 s after receiving the alert, making it the fastest optical detection of a GRB from a GBM error-box. Spectroscopy obtained with the 10.4-m Gran Telescopio Canarias and the 6-m Big Telescope Alt-azimuth of the Special Astrophysical Observatory of the Russian Academy of Sciences reveals a redshift of z = 1.32. We performed optical and near-infrared photometry of GRB 140801A using different telescopes with apertures ranging from 0.4 to 10.4 m. GRB 140801A is a typical burst in many ways. The rest-frame bolometric isotropic energy release and peak energy of the burst are ... erg and ..., respectively, which is consistent with the Amati relation. The absence of a jet break in the optical light curve provides a lower limit on the half-opening angle of the ... The observed ... is consistent with the limit derived from the Ghirlanda relation. The joint Fermi GBM and Konus-Wind analysis show that GRB 140801A could belong to the class of intermediate duration. The rapid detection of the optical counterpart of GRB 140801A is especially important regarding the upcoming experiments with large coordinate error-box areas. (ProQuest: ... denotes formulae/symbols omitted.)
The EAS Cherenkov array Tunka-133, with about 3km2 sensitive area, has been installed in the Tunka Valley, Siberia. The accessible energy range is 1015–1018eV. In this contribution, a description of ...the array and main results obtained so far are presented. A current update of the array includes the deployment of scintillation stations, radio antennas, as well as optical stations. The deployments of these optical stations are the first step towards Tunka-HiSCORE, a wide-angle, large field-of-view gamma-ray telescope.
We present the results of the prompt, early and afterglow optical observations of five γ-ray bursts (GRBs): GRB 100901A, GRB 100902A, GRB 100905A, GRB 100906A and GRB 101020A. These observations were ...made with the Mobile Astronomical System of TElescope-Robots in Russia (MASTER-II Net), the 1.5-m telescope of the Sierra Nevada Observatory and the 2.56-m Nordic Optical Telescope. For two sources, GRB 100901A and GRB 100906A, we detected optical counterparts and obtained light curves starting before the cessation of γ-ray emission, at 113 and 48 s after the trigger, respectively. Observations of GRB 100906A were conducted in two polarizing filters. Observations of the other three bursts gave the upper limits on the optical flux; their properties are briefly discussed. A more detailed analysis of GRB 100901A and GRB 100906A, supplemented by Swift data, provides the following results and indicates different origins for the prompt optical radiation in the two bursts. The light-curve patterns and spectral distributions suggest that there is a common production site for the prompt optical and high-energy emission in GRB 100901A. The results of the spectral fits for GRB 100901A in the range from optical to X-ray favour power-law energy distributions and a consistent value of the optical extinction in the host galaxy. GRB 100906A produced a smoothly peaking optical light curve, suggesting that the prompt optical radiation in this GRB originated in a front shock. This is supported by a spectral analysis. We have found that the Amati and Ghirlanda relations are satisfied for GRB 100906A. We obtain an upper limit on the value of the optical extinction on the host of GRB 100906A.
The Cherenkov light array for the registration of extensive air showers (EAS) Tunka-133 collected data during 5 winter seasons from 2009 to 2014. The differential energy spectrum of all particles and ...the dependence of the average maximum depth on the energy in the range of 6 ⋅ 1015–1018 eV measured for 1540 hours of observation are presented.
Tunka-Rex, the Tunka radio extension, is an array of about 20 antennas currently under construction, which covers an area of 1 km2. Tunka-Rex measures the radio emission of cosmic-ray air showers ...above 1016 eV. It is triggered by the photomultipliers of the Tunka-133 experiment which simultaneously measure the Cherenkov light emitted by the same air showers. The radio-Cherenkov-hybrid measurements thus offer a unique opportunity for a cross-calibration of both detection methods. The main goal of Tunka-Rex is to determine the precision of the radio reconstruction for the energy and the atmospheric depth of the shower maximum, Xmax, and thus to experimentally test theoretical predictions that the radio precision can be similar to the precision of air-Cherenkov and fluorescence measurements. At the same time, Tunka-Rex can demonstrate that radio measurements can be performed on a large area for a relatively cheap price, since the antennas will be connected to the already existing Tunka DAQ. Finally, radio-antenna arrays have the perspective to increase the effective observation time compared to air-Cherenkov and fluorescence detectors by an order of magnitude, since radio measurements are possible under almost any atmospheric and light conditions.
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