arXiv subjects

N. M. Budnev

Publications and source records attributed to N. M. Budnev.

At least 55 records · Page 3Linked to original sources

arXiv2021

Automatic data processing for Baikal-GVD neutrino observatory

Baikal-GVD is a gigaton-scale neutrino observatory under construction in Lake Baikal. It currently produces about 100 GB of data every day. For their automatic processing, the Baikal Analysis and Reconstruction software (BARS) was developed. At the moment, it includes such stages as hit extraction from PMT waveforms, assembling events from raw data, assigning timestamps to events, determining the position of the optical modules using an acoustic positioning system, data quality monitoring, muon track and cascade reconstruction, as well as the alert signal generation. These stages are implemented as C++ programs which are executed sequentially one after another and can be represented as a directed acyclic graph. The most resource-consuming programs run in parallel to speed up processing. A separate Python package based on the luigi package is responsible for program execution control. Additional information such as the program execution status and run metadata are saved into a central database and then displayed on the dashboard. Results can be obtained several hours after the run completion.

astro-ph.IM↗

arXiv2021

The Baikal-GVD neutrino telescope as an instrument for studying Baikal water luminescence

We present data on the Baikal water luminescence collected with the Baikal-GVD neutrino telescope. This three-dimensional array of photo-sensors allows the observation of time and spatial variations of the ambient light field. We report on annual increase of luminescence activity in years 2018-2020. We observed a unique event of a highly luminescent layer propagating upwards with a maximum speed of 28 m/day for the first time.

hep-ph↗

arXiv2021

The primary cosmic-ray energy spectrum measured with the Tunka-133 array

The EAS Cherenkov light array Tunka-133, with $\sim$ 3 km$^2$ geometric area, is taking data since 2009.The array permits a detailed study of energy spectrum and mass composition of cosmic rays in the energy range from $6\cdot 10^{15}$ to $10^{18}$ eV. We describe the methods of time and amplitude calibration of the array and the methods of EAS parameters reconstruction. We present the all-particle energy spectrum, based on 7 seasons of operation.

astro-ph.HE↗

arXiv2020

Optical Observations Reveal Strong Evidence for High Energy Neutrino Progenitor

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).

astro-ph.HE↗

arXiv2020

Lowly polarized light from a highly magnetized jet of GRB 190114C

We report multi-color optical imaging and polarimetry observations of the afterglow of the first TeV- detected gamma-ray burst, GRB 190114C, using RINGO3 and MASTER II polarimeters. Observations begin 31 s after the onset of the GRB and continue until $\sim 7000\,$s post-burst. The light curves reveal a chromatic break at $\sim 400- 500\,$s, with initial temporal decay $α= 1.669 \pm 0.013$ flattening to $α\sim 1$ post-break, which we model as a combination of reverse and forward-shock components, with magnetization parameter $R_{\rm B} \sim 70$. The observed polarization degree decreases from $7.7 \pm 1.1\%$ to $2-4\%$ during $52-109\,$s post-burst and remains steady at this level for the subsequent $\sim 2000$-s, at constant position angle. Broadband spectral energy distribution modeling of the afterglow confirms GRB 190114C is highly obscured (A$_{\rm v, HG} = 1.49 \pm 0.12 \,$mag; N$_{\rm H, HG}= (9.0 \pm 0.3) \times 10^{22}\,$cm$^{-2}$). We interpret the measured afterglow polarization as intrinsically low and dominated by dust, in contrast to ${\rm P} >10\%$ measured previously for other GRB reverse shocks, with a small contribution from polarized prompt photons in the first minute. We test whether 1st and higher-order inverse Compton scattering in a magnetized reverse shock can explain the low optical polarization and the sub-TeV emission but conclude neither is explained in the reverse shock Inverse Compton model. Instead, the unexpectedly low intrinsic polarization degree in GRB 190114C can be explained if large-scale jet magnetic fields are distorted on timescales prior to reverse shock emission.

astro-ph.HE↗

arXiv2019

Multiwavelength observations of GRB 140629A. A long burst with an achromatic jet break in the optical and X-ray afterglow

We investigate the long GRB140629A through multiwavelength observations, which cover optical, infrared and X-rays between 40s and 3yr after the burst, to derive the properties of the dominant jet and its host galaxy. 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. 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 to be 7.2x10^21cm^-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 0.4d 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 6.7deg viewed 3.8deg off-axis, which released a total energy of 1.4x10^54erg. 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 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 logSFR=1.1^+0.9_-0.4Myr^-1. We obtain a value of the neutral hydrogen density by fitting the optical spectrum, logN(HI)=21.0+-0.3, classifying this host as a damped Lyman-alpha. High ionisation lines are also detected in the spectrum.

astro-ph.HE↗

arXiv2019

Data Quality Monitoring system in the Baikal-GVD experiment

The quality of the incoming experimental data has a significant importance for both analysis and running the experiment. The main point of the Baikal-GVD DQM system is to monitor the status of the detector and obtained data on the run-by-run based analysis. It should be fast enough to be able to provide analysis results to detector shifter and for participation in the global multi-messaging system.

astro-ph.IM↗

arXiv2019

The optical noise monitoring systems of Lake Baikal environment for the Baikal-GVD telescope

We present data on the luminescence of the Baikal water medium collected with the Baikal-GVD neutrino telescope. This three-dimensional array of light sensors allows the observation of time and spatial variations of the ambient light field. We report on observation of an increase of luminescence activity in 2016 and 2018. On the contrary, we observed practically constant optical noise in 2017. An agreement has been found between two independent optical noise data sets. These are data collected with online monitoring system and the trigger system of the cluster.

astro-ph.HE↗

arXiv2019

Neutrino Telescope in Lake Baikal: Present and Future

A significant progress in the construction and operation of the Baikal Gigaton Volume Detector in Lake Baikal, the largest and deepest freshwater lake in the world, is reported. The effective volume of the detector for neutrino initiated cascades of relativistic particles with energy above 100 TeV has been increased up to about 0.25 cubic kilometer. This unique scientific facility, the largest operating neutrino telescope in Northern Hemisphere, allows already to register two to three events per year from astrophysical neutrinos with energies exceeding 100 TeV. Preliminary results obtained with data recorded in 2016-2018 are announced. Multimessenger approach is used to relate finding of cosmic neutrinos with those of classical astronomers, with X-ray or gamma-ray observations and the gravitational wave events.

astro-ph.HE↗

arXiv2019

Search for cascade events with Baikal-GVD

Baikal-GVD is a next generation, kilometer-scale neutrino telescope currently under construction in Lake Baikal. GVD is formed by multi-megaton sub-arrays (clusters) and is designed for the detection of astrophysical neutrino fluxes at energies from a few TeV up to 100 PeV. The design of the Baikal-GVD allows one to search for astrophysical neutrinos with flux values measured by IceCube already at early phases of the array construction. We present here preliminary results of the search for high-energy neutrinos via the cascade mode with the Baikal-GVD neutrino telescope.

astro-ph.HE↗

arXiv2019

The Baikal-GVD neutrino telescope: First results of multi-messenger studies

Multi-messenger astronomy is a powerful tool to study the physical processes driving the non-thermal Universe. A combination of observations in cosmic rays, neutrinos, photons of all wavelengths and gravitational waves is expected. The alert system of the Baikal-GVD detector under construction will allow for a fast, on-line reconstruction of neutrino events recorded by the Baikal-GVD telescope and - if predefined conditions are satisfied - for the formation of an alert message to other communities. The preliminary results of searches for high-energy neutrinos in coincidence with GW170817/GRB170817A using the cascade mode of neutrino detection are discussed. Two Baikal-GVD clusters were operating during 2017. The zenith angle of NGC 4993 at the detection time of the GW170817 was 93.3 degrees. No events spatially coincident with GRB170817A were found. Given the non-detection of neutrino events associated with GW170817, upper limits on the neutrino fluence were established.

astro-ph.HE↗

arXiv2019

The Baikal-GVD detector calibration

In April 2019, the Baikal-GVD collaboration finished the installation of the fourth and fifth clusters of the neutrino telescope Baikal-GVD. Momentarily, 1440 Optical Modules (OM) are installed in the largest and deepest freshwater lake in the world, Lake Baikal, instrumenting 0.25 cubic km of sensitive volume. The Baikal-GVD is thus the largest neutrino telescope on the Northern Hemisphere. The first phase of the detector construction is going to be finished in 2021 with 9 clusters, 2592 OMs in total, however the already installed clusters are stand-alone units which are independently operational and taking data from their commissioning. Huge number of channels as well as strict requirements for the precision of the time and charge calibration (ns, p.e.) make calibration procedures vital and very complex tasks. The inter cluster time calibration is performed with numerous calibration systems. The charge calibration is carried out with a Single Photo-Electron peak. The various data acquired during the last three years in regular and special calibration runs validate successful performance of the calibration systems and of the developed calibration techniques. The precision of the charge calibration has been improved and the time dependence of the obtained calibration parameters have been cross-checked. The multiple calibration sources verified a 1.5 - 2.0 ns precision of the in-situ time calibrations. The time walk effect has been studied in detail with in situ specialized calibration runs.

astro-ph.IM↗

arXiv2019

A positioning system for Baikal-GVD

A cubic kilometer scale neutrino telescope Baikal-GVD is currently under construction in Lake Baikal. Baikal-GVD is designed to detect Cerenkov radiation from products of astrophysical neutrino interactions with Baikal water by a lattice of photodetectors submerged between the depths of 1275 and 730 m. The detector components are mounted on flexible strings and can drift from their initial positions upwards to tens of meters. This introduces positioning uncertainty which translates into a timing error for Cerenkov signal registration. A spatial positioning system has been developed to resolve this issue. In this contribution, we present the status of this system, results of acoustic measurements and an estimate of positioning error for an individual component.

astro-ph.IM↗

arXiv2019

The inter-cluster time synchronization systems within the Baikal-GVD detector

Currently in Lake Baikal, a new generation neutrino telescope is being deployed: the deep underwater Cherenkov detector of a cubic-kilometer scale Baikal-GVD. Completion of the first stage of the telescope construction is planned for 2021 with the implementation of 9 clusters. Each cluster is a completely independent unit in all the aspects: triggering, calibration, data transfer, etc. A high-energy particle might leave its trace in more than a single cluster. To be able to merge events caused by such a particle in more clusters, the appropriate inter-cluster time synchronization is vital.

physics.ins-det↗

arXiv2019

Signal recognition and background suppression by matched filters and neural networks for Tunka-Rex

The Tunka Radio Extension (Tunka-Rex) is a digital antenna array, which measures the radio emission of the cosmic-ray air-showers in the frequency band of 30-80 MHz. Tunka-Rex is co-located with TAIGA experiment in Siberia and consists of 63 antennas, 57 of them are in a densely instrumented area of about 1 km\textsuperscript{2}. In the present work we discuss the improvements of the signal reconstruction applied for the 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 performance of 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 trace, i.e. removes all signal-unrelated amplitudes. We present the comparison between standard method of signal reconstruction, matched filtering and autoencoder, and discuss the prospects of application of neural networks for lowering the threshold of digital antenna arrays for cosmic-ray detection.

astro-ph.IM↗

arXiv2019

Current Status and New Challenges of The Tunka Radio Extension

The Tunka Radio Extension (Tunka-Rex) is an antenna array spread over an area of about 1~km$^2$. The array is placed at the Tunka Advanced Instrument for cosmic rays and Gamma Astronomy (TAIGA) and detects the radio emission of air showers in the band of 30 to 80~MHz. During the last years it was shown that a sparse array such as Tunka-Rex is capable of reconstructing the parameters of the primary particle as accurate as the modern instruments. Based on these results we continue developing our data analysis. Our next goal is the reconstruction of cosmic-ray energy spectrum observed only by a radio instrument. Taking a step towards it, we develop a model of aperture of our instrument and test it against hybrid TAIGA observations and Monte-Carlo simulations. In the present work we give an overview of the current status and results for the last five years of operation of Tunka-Rex and discuss prospects of the cosmic-ray energy estimation with sparse radio arrays.

astro-ph.IM↗

arXiv2018

A search for neutrino signal from dark matter annihilation in the center of the Milky Way with Baikal NT200

We reanalyze the dataset collected during the years 1998--2003 by the deep underwater neutrino telescope NT200 in the lake Baikal with the low energy threshold (10 GeV) in searches for neutrino signal from dark matter annihilations near the center of the Milky Way. Two different approaches are used in the present analysis: counting events in the cones around the direction towards the Galactic Center and the maximum likelihood method. We assume that the dark matter particles annihilate dominantly over one of the annihilation channels $b\bar{b}$, $W^+W^-$, $τ^+τ^-$, $μ^+μ^-$ or $ν\barν$. No significant excess of events towards the Galactic Center over expected neutrino background of atmospheric origin is found and we derive 90% CL upper limits on the annihilation cross section of dark matter.

astro-ph.HE↗

arXiv2018

First analysis of inclined air showers detected by Tunka-Rex

The Tunka Radio Extension (Tunka-Rex) is a digital antenna array for the detection of radio emission from cosmic-ray air showers in the frequency band of 30 to 80 MHz and for primary energies above 100 PeV. The standard analysis of Tunka-Rex includes events with zenith angle of up to 50$^\circ$. This cut is determined by the efficiency of the external trigger. However, due to the air-shower footprint increasing with zenith angle and due to the more efficient generation of radio emission (the magnetic field in the Tunka valley is almost vertical), there are a number of ultra-high-energy inclined events detected by Tunka-Rex. In this work we present a first analysis of a subset of inclined events detected by Tunka-Rex. We estimate the energies of the selected events and test the efficiency of Tunka-Rex antennas for detection of inclined air showers.

astro-ph.IM↗