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The Baikal-GVD neutrino telescope, located in Lake Baikal, Russia, is designed to detect high-energy neutrinos and perform real-time searches for astrophysical sources associated with multimessenger signals, such as gamma-ray bursts, gravitational waves, and neutrino alerts. Since 2021, the implementation of an automated system has reduced analysis delays to 3-10 minutes, enabling efficient classification of events into upward-going tracks (muon neutrinos) and high-energy cascades (all-flavor neutrinos). The telescope’s external alert follow-up system employs InfluxDB for time-series data management and Grafana for online data visualization and correlation analysis. Using ON/OFF algorithms and techniques for identifying spatial-temporal coincidences, the real-time system detects potential signals and evaluates their significance using the maximum likelihood method. In cases where no significant signal is detected, upper limits on neutrino fluxes are calculated.

The Baikal-GVD deep-sea Cherenkov detector, whose deployment in Lake Baikal has been ongoing since 2016, currently represents the largest neutrino telescope in the Northern Hemisphere. The principle of the telescope’s operation is based on the registration of Cherenkov radiation produced by the products of neutrino interaction in the aquatic environment using the spatial structure of photodetectors. Laser light sources specially designed for the Baikal project are used to calibrate and measure the characteristics of the telescope’s detecting system. The article describes the design and features of the functioning of calibration laser sources, presents the results of their operation as part of the telescope, and discusses issues of further development of the laser-calibration system.

A brief analytical review of isolated industrial inflows of oil and gas in a number of areas of the Republic of Sakha (Yakutia): Buyaginsky, Kederginsky, Russkorechensky and South Tigyansky. The recorded industrial inflows were suggested to be confined to zones of “flower-type“discontinuous violations. In all the considered areas, promising structures are or were located in zones of subhorizontal tectonic compression and shear stress. As an example, the features of the oil and gas potential of the Yuzhno-Tigyansk heavy oil field are considered in more detail. The model of the “flower type” structure and its isolated industrial oil flow in the South-Tigyansky area. Based on the proposed model of oil and gas potential of the areas, the conclusion is made about the direction of geological exploration in the “flower” structures to the lower potentially feeding areas of the subsurface.

Currently, the Baikal-GVD Deep Underwater Neutrino Telescope is being successfully deployed in Lake Baikal. It comprises 96 strings with 3456 optical modules. We present the status and plans for further deployment of the Baikal-GVD telescope and discuss the issues related to the development of the next-generation neutrino telescope in Lake Baikal.

This paper proposes a method for separation the light component of cosmic rays in the energy range of 200 TeV–20 PeV (the knee region in the PCR spectrum) from hybrid events detected by two Cherenkov setups IACT + HiSCORE in TAIGA experiment. The possibility of such separation is demonstrated using Monte Carlo calculations and the first experimental estimates are made.

This paper presents the results of an analysis of observations of the Crab Nebula gamma-ray source with the first two atmospheric Cherenkov telescopes of the TAIGA (Tunka Advanced Instrument for cosmic ray physics and Gamma Astronomy) astrophysical complex in the stereo mode of observations. The article analyzed observational data from 2020 to 2021. Over 36 hours of observations, a signal was obtained at a statistical significance level of 5 and a spectrum of gamma rays was plotted in the energy range from 2 to 70 TeV. The paper describes a technique for gamma–hadron separation and reconstruction of detected gamma-rays energy.

The neutrino telescope Baikal-GVD is designed for search for high energy neutrinos whose sources are not yet reliably identified. It currently includes total of 3456 optical modules arranged on 96 strings, providing an effective volume of 0.6 km for cascades with energy above 1 PeV. We discuss the first results from the partially built experiment, which is currently the largest neutrino telescope in the Northern Hemisphere and still growing up.

Baikal-GVD has recently published its first measurement of the diffuse astrophysical neutrino flux, performed using high-energy cascade-like events. We further explore the Baikal-GVD cascade dataset collected in 2018-2022, with the aim to identify possible associations between the Baikal-GVD neutrinos and known astrophysical sources. We leverage the relatively high angular resolution of the Baikal-GVD neutrino telescope (2-3 deg.), made possible by the use of liquid water as the detection medium, enabling the study of astrophysical point sources even with cascade events. We estimate the telescope's sensitivity in the cascade channel for high-energy astrophysical sources and refine our analysis prescriptions using Monte-Carlo simulations. We primarily focus on cascades with energies exceeding 100 TeV, which we employ to search for correlation with radio-bright blazars. Although the currently limited neutrino sample size provides no statistically significant effects, our analysis suggests a number of possible associations with both extragalactic and Galactic sources. Specifically, we present an analysis of an observed triplet of neutrino candidate events in the Galactic plane, focusing on its potential connection with certain Galactic sources, and discuss the coincidence of cascades with several bright and flaring blazars.

The physical motivations and performance of the TAIGA (Tunka Advanced Instrument for cosmic ray physics and Gamma Astronomy) project are presented. The TAIGA observatory addresses ground-based gamma-ray astronomy at energies from a few TeV to several PeV, as well as cosmic ray physics from 100 TeV to several EeV and astroparticle physics. The pilot TAIGA-1 complex locates in the Tunka valley, km West from the southern tip of the lake Baikal. It includes integrated air Cherenkov TAIGA-HiSCORE array with 120 wide-angle optical stations distributed over on area 1.1 square kilometer about and three 4-m class Imaging Atmospheric Cherenkov Telescopes of the TAIGA-IACT array. The latter array has a shape of triangle with side lengths of about 300, 400 and 500 m. The integral sensitivity of the 1-km TAIGA-1 detector is about TeV cm s for detection of TeV gamma-rays in 300 hours of source observations. The combination of the wide-angle Cherenkov array and IACTs could offer a cost effective-way to build a large (up to 10 km ) array for very high energy gamma-ray astronomy. The reconstruction of a given EAS energy, incoming direction, and the core position, based on the TAIGA-HiSCORE data, allows one to increase the distance between the relatively expensive IACTs up to 600–800 m. These, together with the surface and underground electron/Muon detectors, will be used for selection of gamma-ray-induced EAS. Present status of the project, together with the current array description, the first experimental results and plans for the future are reported.

The TAIGA gamma observatory is continuing its deployment at the Tunka valley, close to lake Baikal. The new, original detectors, able to work under severe conditions of Siberia, were developed to increase the TAIGA sensitivity for the study of gamma-quanta at energies about 1 PeV and above. The distinguishing feature of the detectors is the use of the wavelength shifting light guides for scintillation light collection on a photodetector. Several designs of the counters have been tested: equipped with PMT or SiPM photo-detectors, acrylic or polystyrene based scintillators with thickness from 1 to 5 cm and detecting area from 0.75 to 1.0 m 2 . The data on the amplitude of the signal from cosmic muons measured in different points within the counter are presented. The first 48 counters were produced and deployed in 2019 at the TAIGA experiment. They form 3 stations each with 8 surface detectors and 8 underground detectors buried at the depth of 1.7 m. After two winters, all counters are working.