arXiv subjects

A. S. Lidvansky

Publications and source records attributed to A. S. Lidvansky.

13 recordsLinked to original sources

arXiv2025

Carpet-3 detection of a photon-like air shower with estimated primary energy above 100 TeV in a spatial and temporal coincidence with GRB 221009A

The brightest cosmic gamma-ray burst (GRB) ever detected, GRB 221009A, was accompanied by photons of very high energies. These gamma rays may be used to test both the astrophysical models of the burst and our understanding of long-distance propagation of energetic photons, including potential new-physics effects. Here we present the observation of a photon-like air shower with the estimated primary energy of $300^{+43}_{-38}$ TeV, coincident (with the chance probability of $\sim 9\cdot 10^{-3}$) with the GRB in its arrival direction and time. Making use of the upgraded Carpet-3 muon detector and new machine learning analysis, we estimate the probability that the primary was hadronic as $\sim 3 \cdot 10^{-4}$. This is the highest-energy event ever associated with any GRB.

astro-ph.HE↗

arXiv2022

Upper limits on the isotropic diffuse flux of cosmic PeV photons from Carpet-2 observations

Isotropic diffuse gamma-ray flux in the PeV energy band is an important tool for multimessenger tests of models of the origin of high-energy astrophysical neutrinos and for new-physics searches. So far, this flux has not yet been observed. Carpet-2 is an air-shower experiment capable of detecting astrophysical gamma rays with energies above 0.1 PeV. Here we report the upper limits on the isotropic gamma-ray flux from Carpet-2 data obtained in 1999-2011 and 2018-2022. These results, obtained with the new statistical method based on the shape of the muon-number distribution, summarize Carpet-2 observations as the upgraded installation, Carpet-3, starts its operation.

astro-ph.HE↗

arXiv2021

Observation of photons above 300 TeV associated with a high-energy neutrino from the Cygnus region

Galactic sites of acceleration of cosmic rays to energies of order 10^15 eV and higher, dubbed PeVatrons, reveal themselves by recently discovered gamma radiation of energies above 100 TeV. However, joint gamma-ray and neutrino production, which marks unambiguously cosmic-ray interactions with ambient matter and radiation, was not observed until now. In November 2020, the IceCube neutrino observatory reported an ~150 TeV neutrino event from the direction of one of the most promising Galactic PeVatrons, the Cygnus Cocoon. Here we report on the observation of a 3.1-sigma (post trial) excess of atmospheric air showers from the same direction, observed by the Carpet-2 experiment and consistent with a few-months flare in photons above 300 TeV, in temporal coincidence with the neutrino event. The fluence of the gamma-ray flare is of the same order as that expected from the neutrino observation, assuming the standard mechanism of neutrino production. This is the first evidence for the joint production of high-energy neutrinos and gamma rays in a Galactic source.

astro-ph.HE↗

arXiv2020

Carpet-2 search for gamma rays above 100 TeV in coincidence with HAWC and IceCube alerts

We report on the search of astrophysical gamma rays with energies in the 100 TeV to several PeV range arriving in directional and temporal coincidence with public alerts from HAWC (TeV gamma rays) and IceCube (neutrinos above ~100 TeV). The observations have been performed with the Carpet-2 air-shower detector at the Baksan Neutrino Observatory, working in the "photon-friendly" mode since 2018. Photon candidate showers are selected by their low muon content. No significant excess of the photon candidates have been observed, and upper limits on gamma-ray fluences associated with the alerts are obtained. For events with good viewing conditions, the Carpet-2 effective area for photons is of the order of the IceCube effective area for neutrinos of the same energy, so the constraints start to probe the production of neutrinos in fast flares of Galactic sources.

astro-ph.HE↗

arXiv2019

Carpet results on astrophysical gamma rays above 100 TeV

Carpet is an air-shower array at Baksan, Russia, equipped with a large-area muon detector, which makes it possible to separate primary photons from hadrons. We report first results of the search for primary photons with energies E>100 TeV. The experiment's ongoing upgrade and future sensitivity are also discussed.

astro-ph.HE↗

arXiv2019

BUST Search for Muon Neutrinos from the Gravitational Wave Event GW170817

Using data of the Baksan Underground Scintillation Telescope (BUST) we have made a search for muon neutrinos and antineutrinos with energies above 1 GeV coinciding with the gravitational wave event GW170817 that was recorded on August 17, 2017 by the Advanced LIGO and Advanced Virgo observatories. This is a first detection of the new type of events occurring as a result of a merger of two neutron stars in a binary system. A short gamma-ray burst GRB170817A accompanying this event is an evidence of particle acceleration in the source whose precise position was determined by detection of the subsequent optical signal. No neutrino signals were found with the BUST in the interval $\pm 500$ s around the moment of the gravitational wave event GW170817, as well as during the next 14 days. The upper limits on integral fluxes of muon neutrino and antineutrino from the source are derived.

astro-ph.HE↗

arXiv2018

Search for astrophysical PeV gamma rays from point sources with Carpet-2

Early results of the search for E_γ>1 PeV cosmic photons from point sources with the data of Carpet-2, an air-shower array equipped with a 175 m^2 muon detector, are presented. They include 95% CL upper limits on PeV photon fluxes from stacked directions of high-energy IceCube neutrino events and from four predefined sources, Crab, Cyg X-3, Mrk 421 and Mrk 501. An insignificant excess of events from Mrk 421 will be further monitored. Prospects of the use of the upgraded installation, Carpet-3 (410 m^2 muon detector), scheduled to start data taking in 2019, for searches of E_γ>100 TeV photons, are briefly discussed.

astro-ph.HE↗

arXiv2018

Carpet-2 search for PeV gamma rays associated with IceCube high-energy neutrino events

Carpet-2 is an air-shower array at Baksan Valley, Russia, equipped with a large-area (175 m^2) muon detector, which makes it possible to separate primary photons from hadrons. We report the first results of the search for primary photons with energies E_γ>1 PeV, directionally associated with IceCube high-energy neutrino events, in the data obtained in 3080 days of Carpet-2 live time.

astro-ph.HE↗

arXiv2015

Search for cosmic gamma rays with the Carpet-2 extensive air shower array

The present-day status of the problem of searching for primary cosmic gamma rays at energies above 100 TeV is discussed, as well as a proposal for a new experiment in this field. It is shown that an increase of the area of the muon detector of the Carpet-2 air shower array up to 410 square meters, to be realized in 2016, will make this array quite competitive with past and existing experiments, especially at modest energies. Some preliminary results of measurements made with smaller area of the muon detector are presented together with estimates of expected results to be obtained with the coming large-area muon detector.

astro-ph.HE↗

arXiv2011

Strong variations of cosmic ray intensity during thunderstorms and associated pulsations of the geomagnetic field

Strong variations of the intensity of secondary cosmic rays during thunderstorms are found to be accompanied in some cases by very clear pulsations of the geomagnetic field. The experiment is carried out in the Baksan Valley, North Caucasus, the Carpet air shower array being used as a particle detector. Magnetic field measurements are made with high-precision magnetometers located deep underground in the tunnel of the Baksan Neutrino Observatory, several kilometers apart from the air shower array.

physics.geo-ph↗

arXiv2008

Anisotropy of Galactic Cosmic Rays and New Discoveries in Its Measurements

We discuss recently published results of two-dimensional measurements of the cosmic ray anisotropy in the energy range 1-100 TeV. It is demonstrated that, in spite of pretence of the authors to measure the anisotropy in more detail than it was done in one-dimensional measurements of the first harmonic of CR intensity in sidereal time, new measurements give nothing essentially new. Moreover, two-dimensional picture is misleading creating an illusion that the true direction of the anisotropy is observed, while, as before, only the projection of the anisotropy onto the equatorial plane is measured and the phase of the anisotropy remains to be the only directly measured parameter. The sophisticated interpretations of the results of 2D measurements made by their authors are invalid, since they are based on the false assumption that the equatorial excess and deficit of CR intensity seen on the difference maps represent the real anisotropy.

astro-ph↗

arXiv2005

Air Cherenkov Methods in Cosmic Rays: A Review and Some History

The history of application of the Cherenkov light emission in the atmosphere to cosmic ray and gamma-ray astronomy studies is briefly outlined with an emphasis on the pioneering activity of A.E. Chudakov. The present-day situation and some new ideas are also discussed.

astro-ph↗

arXiv2004

Mean diurnal variations of cosmic ray intensity as measured by Andyrchi air shower array and Baksan underground scintillation telescope

The results of measuring diurnal variations of extensive air showers with energy above 100 TeV detected by the Andyrchi air shower array in 1995-2002 are presented. It is shown that solar diurnal wave of intensity is formed by pressure variations and Compton-Getting effect (due to the orbital motion of the Earth). The data on cosmic ray anisotropy of the Baksan underground scintillation telescope (BUST) are also presented for energies above 2.5 TeV covering the period 1982-1998. The diurnal sidereal wave measured by both Andyrchi and BUST is due to anisotropy of the cosmic rays.

astro-ph↗