GRB 221009A was a remarkable gamma-ray burst; it is sometimes referred to as “the brightest of all time” (BOAT). In this talk we consider two peculiar components of observable gamma-rays from GRB 221009A: 1) a high energy “echo” of the GRB
prompt emission phase produced by neutrons from photohadronic interactions inside the fireball with subsequent interaction of these neutrons with the...
Some neutron stars are located in low-mass X-ray binaries (LMXBs), i.e. have low-mass companions. In these systems, matter from the companion is transferred via Roche-lobe overflow and accretes onto the neutron star. The accretion process can be either transient or persistent. During accretion, the previously accreted material is compressed under the weight of newly accreted matter. In the...
Among the scenarios for the evolution of various astrophysical objects in which the conditions necessary for the r‑process to occur can be realized, the process of neutron star mergers in a close binary system is currently considered the main one [1]. This scenario largely depends on the masses of the objects included in the system and can develop in different ways: 1) If neutron stars have...
Axion-like particles (ALPs) are a class of hypothetical bosons beyond the standard model of particle physis, which are
very weakly-interacting and long- lived. Since many ALPs may be produced in hot plasma in supernovae (SNe), a nearby
SNe Ia can be used as a probe of ALPs. It is desirable to predict the ALP emission from SNe Ia to discuss a possible
constraint that can be obtained from the...
Abstract: The paper theoretically investigates the equilibrium structure of neutron stars consisting of degenerate relativistic neutron gas, based on the equation of radial mass distribution. The thermodynamic properties of a relativistic Fermi gas are studied, and a relationship between the compressibility coefficient and the particle concentration is established without taking nuclear forces...
While Standard Model extensions such as Supersymmetry have long provided promising candidates, the absence of supersymmetric particle signals at the LHC and contradictory results from direct detection experiments motivate exploration of alternative scenarios. The hypothesis of composite dark atoms — electrically neutral atom-like bound states formed by stable doubly negatively charged...
This paper discusses the historical evidence for the light jets from the central Super Massive Black Hole of Galaxy in the 4th and 14th centuries. We suggest that the apparitions of a "lightening cross" recorded in 312, 351, 1317 and 1377 years were caused by the line of two jets beamed back-to-back from the center of Milky Way (MW), which is crossing the visible projection of the Galaxy disk....
High-energy astrophysical neutrinos can provide a probe of hadronic processes at their production site constraining models of the most energetic cosmic ray sources. The diffuse astrophysical neutrino flux was discovered by the IceCube experiment more than a decade ago but still remains largely unexplored. After the deployment campaign in 2026, the Baikal-GVD neutrino telescope has reached the...
The High-energy Underwater Neutrino Telescope (HUNT) project aims to identify astrophysical neutrino sources, particularly those associated with ultra-high-energy gamma-ray emission observed by LHAASO. We present the status of its prototype program in Lake Baikal, covering deployment campaigns and preliminary results from 2024 to 2026. Deployments progressed from 12 optical modules with...
We investigate and make theoretical estimates for the neutrino flux above 150 TeV in a scenario with a nearby source in the Cygnus region, the existence of which is motivated by the LHAASO gamma-ray bubble observations. By combining a state-of-the-art model of galactic cosmic rays with the contribution from a local source within the framework of a two-zone diffusion model, we investigate the...
The formation of a neutrino cluster due to an attractive interaction with a hypothetical light scalar boson is studied. The density distribution of the neutrino gas within the cluster is obtained for various system parameters. It is shown that, in addition to forming a cluster in space, the neutrino gas within it can form a superfluid condensate. An energy gap equation is derived for such a...
Strange quark matter (SQM) is a compelling candidate for the true ground state of quantum chromodynamics (QCD) at high baryon density. Within the Bodmer-Witten-Terazawa hypothesis, if SQM has a lower energy per baryon than ordinary hadronic matter, neutron stars can convert to strange quark stars (SQSs). Stable clusters of SQM, strangelets, can be produced in dense QCD phase transitions,...
Red-giant evolution is sensitive to non-standard channels of energy loss and therefore provides a probe of new physics.
Such losses increase the luminosity of the tip of the red-giant branch
(TRGB), enabling constraints on the axion--electron coupling $g_{ae}$.
In this talk, we present cluster-specific stellar-evolution calculations
with MESA for 27 Galactic globular clusters, including the...
Star formation processes are very important in the Universe. In particular, the formation of massive stars results in supernova explosions with subsequent acceleration of cosmic rays (CR) in supernova remnants (SNRs). We show that the currently-available elemental spectra of protons, Helium, CNO group nuclei, and Iron in the energy range from 40 GeV to 100--500 PeV are well described with two...
Astrophysical sources of ultra-high-energy cosmic rays (UHECRs) remain unidentified, and no nearby cosmic accelerators are established even for the highest-energy events. In addition, puzzling correlations of a fraction of UHECR flux with distant blazars were found by HiRes and, recently, Telescope Array experiments. Here we propose that dark matter can provide a mechanism to effectively...
The Telescope Array (TA) is the largest cosmic-ray observatory in the Northern Hemisphere and it is dedicated to studying the origin and properties of cosmic rays over a wide energy range. The experiment consists of two types of detectors: a surface array of scintillation detectors and telescopes designed to detect fluorescence and Cherenkov light. Together with its low-energy extension, TALE,...
We use a new method of ultra-high energy cosmic rays anisotropy analysis to infer their injected mass composition from the data. We use the data of the Telescope Array experiment and public data of the Pierre Auger experiment. Our results show that a light composition is disfavored at all energies above 10 EeV, unless the extragalactic magnetic field is extremely strong.
The origin of ultra-high-energy cosmic rays (UHECRs) remains an open problem. In particular, the properties of their sources are difficult to constrain due to the limited statistics of observed events and the propagation effects experienced by charged cosmic rays. One of the important characteristics of sources is their number density. In this work, we investigate the possibility of...
Modern experiments provide a wealth of new data and reveal many new, still unexplained phenomena. To explain them, one needs a deep understanding of Galactic cosmic ray (GCR) transport, which is usually assumed to be diffusive. Many studies construct predictive models within different variants of this approach and achieve valuable results in explaining observed GCR spectra. However, the...
Most energy measurement methods used in modern experiments are based on the cascade curve, i.e., the dependence of the cascade size (typically expressed as the logarithm of the energy deposition, log q, in a given calorimeter layer) on the penetration depth (d) of the cascade into that layer. If the cascade curve reaches its maximum within the calorimeter, the primary energy can be...
A basis of the Experimental Complex NEVOD (MEPhI, Moscow) is the Cherenkov water calorimeter (CWC) with a volume of 2000 m3. The quasi-spherical modules (QSMs) consisting of 6 orthogonally oriented photomultiplier tubes (PMTs) are used to detect Cherenkov radiation. The CWC NEVOD includes 91 QSMs (546 PMTs in total) which form a spatial grid in the water volume with 25 vertically arranged...
The SPHERE-3 experiment is being developed to study the mass composition of primary cosmic rays using Cherenkov light from extensive air showers reflected from the snow surface. The lateral distribution of this light carries information about the primary mass, but its interpretation depends on the atmospheric profile and the hadronic interaction model used in shower simulations.
We present a...
Photonuclear interactions are the main source of high-energy muons in gamma-ray-induced extensive air showers (EASs), while the corresponding cross section remains poorly constrained at energies relevant for astrophysical gamma rays. We develop an efficient framework for propagating uncertainties in the photonuclear cross section to the muon content and photon-selection efficiency of EAS...
