arXiv subjects

A. Neronov

Publications and source records attributed to A. Neronov.

At least 37 records · Page 2Linked to original sources

arXiv2024

Resistively controlled primordial magnetic turbulence decay

Magnetic fields generated in the early Universe undergo turbulent decay during the radiation-dominated era. The decay is governed by a decay exponent and a decay time. It has been argued that the latter is prolonged by magnetic reconnection, which depends on the microphysical resistivity and viscosity. Turbulence, on the other hand, is not usually expected to be sensitive to microphysical dissipation, which affects only very small scales. We want to test and quantify the reconnection hypothesis in decaying hydromagnetic turbulence. We performed high-resolution numerical simulations with zero net magnetic helicity using the Pencil Code with up to $2048^3$ mesh points and relate the decay time to the Alfvén time for different resistivities and viscosities. The decay time is found to be longer than the Alfvén time by a factor that increases with increasing Lundquist number to the 1/4 power. The decay exponent is as expected from the conservation of the Hosking integral, but a timescale dependence on resistivity is unusual for developed turbulence and not found for hydrodynamic turbulence. In two dimensions, the Lundquist number dependence is shown to be leveling off above values of $\approx25,000$, independently of the value of the viscosity. Our numerical results suggest that resistivity effects have been overestimated in earlier work. Instead of reconnection, it may be the magnetic helicity density in smaller patches that is responsible for the resistively slow decay. The leveling off at large Lundquist number cannot currently be confirmed in three dimensions.

astro-ph.CO↗

arXiv2024

Constraint on magnetized galactic outflows from LOFAR rotation measure data

Outflows from galaxies, driven by active galactic nuclei and star formation activity, spread magnetic fields into the intergalactic medium. Importance of this process can be assessed using cosmological magneto-hydrodynamic numerical modelling of the baryonic feedback on the Large Scale Structure, like that of Illustris-TNG simulations. We use the Faraday Rotation Measure data of LOFAR Two-Meter Sky Survey (LOTSS) to test the Illustris-TNG baryonic feedback model. We show that the Illustris-TNG over-predicts the root-mean-square of the residual Rotation Measure in LOTSS. This suggests that the "pollution" of the intergalactic medium by the magnetized outflows from galaxies is less important than the estimate from the Illustris-TNG. This fact provides a support to the hypothesis that the volume-filling large scale magnetic fields found in the voids of the Large Scale Structure are likely of cosmological origin.

astro-ph.CO↗

arXiv2023

Energy-dependent periodicities of LS I +61$^\circ$ 303 in the GeV band

LS I +61$^\circ$303 is a rare representative of the gamma-ray binaries with a compact object known to be a pulsar. We report on the periodicity and spectral analysis of this source performed with more than 14 years of Fermi/LAT data. The periodicity of LS I +61$^\circ$303 is strongly energy dependent. Two periods $P_1 = 26.932\pm 0.004 (stat)\pm 0.008 (syst)$ and $P_2 = 26.485 \pm 0.004 (stat)\pm 0.007 (syst)$ are detected only at $E>1$ GeV and at $E<0.3$ GeV correspondingly. Within $1σ$ (stat+syst) the periods are consistent with orbital ($P_2$) and beat orbital/superorbital ($P_1$) periods. We present the orbital light curves of the system in several energy bands and the results of the spectral analysis. We discuss the possible origin of the change in the variability pattern between 0.1 and 1 GeV energy.

astro-ph.HE↗

arXiv2023

Hadronic nature of high-energy emission from the Galactic Ridge

We show that the IceCube observation of the Galactic neutrino flux component confirms the hint of detection of neutrinos from the Galactic Ridge (the inner part of the Milky Way disk within the Galactic longitude |l|<30 degrees), previously reported by the ANTARES collaboration. This confirmation indicates that the bulk of the high-energy flux from the Galactic Ridge in multi-TeV band is produced by interactions of high-energy protons and atomic nuclei, rather than electrons. We show that both ANTARES and IceCube measurements agree with the Fermi-LAT telescope measurements of the gamma-ray emission from the Ridge. The multi-messenger (neutrino plus gamma-ray) spectrum of the Ridge over a broad energy range from 10 GeV to 10 TeV is consistent with a model of pion decay emission produced by a power-law distribution of protons with a slope Gamma~2.5, harder than that of the locally observed cosmic ray spectrum. This provides for the first time an unambiguous multi-messenger demonstration of the variability of the spectrum of cosmic rays across the Galactic disk.

astro-ph.HE↗

arXiv2023

Measurement of size of gamma-ray source in blazar B0218+357 from microlensing at 100 GeV energy

Observations of the effect of microlensing in gravitationally lensed quasars can be used to study the structure of active galactic nuclei on distance scales down to the sizes of the supermassive black holes powering source activity. We search for the microlensing in the signal from a gravitationally lensed blazar B0218+357 in very-high-energy gamma-ray band. We combine observations of a bright flare of the source in 2014 with Fermi/LAT and MAGIC telescopes in 0.1-100 GeV energy range. Using the time-delayed leading and trailing signals from two gravitationally lensed images of the source, we measure magnification factor at the moment of the flare. We use the scaling of the maximal magnification factor with the source size to constrain the size of gamma-ray emission region in the entire 0.1-100 GeV energy range. The magnification factor in the very-high-energy band derived from a comparison of Fermi/LAT and MAGIC data is $μ_{VHE} = 36^{+40}_{-26}$, substantially larger than that in the radio band. This suggests that one of the source images is strongly affected by microlensing at the moment of the flare. Assuming that the microlensing is produced by a stellar mass object in the lens galaxy, we constrain the size of the emission region in the $E>100$ GeV band to be $\mathrm{R_{VHE} = 2.2^{+27}_{-1.7} \times 10^{13}~cm}$. We note that the spectrum of the microlensed source was unusually hard at the moment of the flare and speculate that this hardening may be due to the energy dependent microlensing effect. This interpretation suggests that the source size decreases with energy in 0.1-100 GeV energy range studied.

astro-ph.HE↗

arXiv2023

Constraint on intergalactic magnetic field from Fermi/LAT observations of the "pair echo" of GRB 221009A

Delayed "pair echo" signal from interactions of very-high-energy gamma rays in the intergalactic medium can be used for detection of the inter-galactic magnetic field (IGMF). We use the data of Fermi/LAT telescope coupled with LHAASO observatory measurements to confirm the presence of IGMF along the line of sight to the gamma-ray burst GRB221009A. Comparing the Fermi/LAT measurements with the expected level of the pair echo flux, set by the multi-TeV LHAASO detection, we derive a lower bound $10^{-19}$ G on the IGMF with correlation length $l$ larger than 1 Mpc, improving as $l^{-1/2}$ for shorter correlation lengths. This provides an independent verification of existence of a lower bound on IGMF in the voids of the Large Scale Structure, previously derived from the observations of active galactic nuclei.

astro-ph.HE↗

arXiv2023

Modelling the propagation of very-high-energy gamma rays with the CRbeam code: Comparison with CRPropa and ELMAG codes

Very-high-energy gamma rays produce electron positron pairs in interactions with low-energy photons of extragalactic background light during propagation through the intergalactic medium. The electron-positron pairs generate secondary gamma rays detectable by gamma-ray telescopes. This secondary emission can be used to detect intergalactic magnetic fields (IGMF) in the voids of large-scale structure. A new gamma-ray observatory, namely, Cherenkov Telescope Array (CTA), will provide an increase in sensitivity for detections of these secondary gamma-ray emission and enable the measurement of its properties for sources at cosmological distances. The interpretation of the CTA data, including detection of IGMF and study of its properties and origins, will require precision modeling of the primary and secondary gamma-ray fluxes. We asses the precision of the modeling of the secondary gamma-ray emission using model calculations with publicly available Monte-Carlo codes CRPropa and ELMAG and compare their predictions with theoretical expectations and with model calculations of a newly developed CRbeam code. We find that model predictions of different codes differ by up to 50% for low-redshift sources, with discrepancies increasing up to order-of-magnitude level with the increasing source redshifts. We identify the origin of these discrepancies and demonstrate that after eliminating the inaccuracies found, the discrepancies between the three codes are reduced to 10% when modeling nearby sources with z~0.1. We argue that the new CRbeam code provides reliable predictions for spectral, timing and imaging properties of the secondary gamma-ray signal for both nearby and distant sources with z~1. Thus, it can be used to study gamma-ray sources and IGMF with a level of precision that is appropriate for the prospective CTA study of the effects of gamma-ray propagation through the intergalactic medium.

astro-ph.HE↗

arXiv2022

Signatures of anisotropic diffusion around PeVatrons in 100 TeV gamma-ray data

The Tibet AS$γ$ collaboration has reported a diffuse $γ$-ray emission signal from the Galactic Plane. We consider the possibility that the diffuse emission from the outer Galactic Plane at the highest energies is produced by cosmic rays spreading from a single supernova-type source either in the Local or Perseus arm of the Milky Way. We show that anisotropic diffusion of multi-PeV cosmic rays along the Galactic magnetic field can produce an extended source spanning ten(s) of degrees on the sky, with a flux-per-unit-solid-angle consistent with Tibet AS$γ$ measurements. Observations of this new type of very extended sources, and measurements of their morphologies, can be used to characterize the anisotropic diffusion of PeV cosmic rays in the Galactic magnetic field, and to constrain the locations and properties of past PeVatrons.

astro-ph.HE↗

arXiv2022

Status of the K-EUSO Orbital Detector of Ultra-high Energy Cosmic Rays

K-EUSO (KLYPVE-EUSO) is a planned orbital mission aimed at studying ultra-high energy cosmic rays (UHECRs) by detecting fluorescence and Cherenkov light emitted by extensive air showers in the nocturnal atmosphere of Earth in the ultraviolet (UV) range. The observatory is being developed within the JEM-EUSO collaboration and is planned to be deployed on the International Space Station after 2025 and operated for at least two years. The telescope, consisting of $\sim10^{5}$ independent pixels, will allow a spatial resolution of $\sim0.6$ km on the ground, and, from a 400 km altitude, it will achieve a large and full sky exposure to sample the highest energy range of the UHECR spectrum. We provide a comprehensive review of the current status of the development of the K-EUSO experiment, paying special attention to its hardware parts and expected performance. We demonstrate how results of the K-EUSO mission can complement the achievements of the existing ground-based experiments and push forward the intriguing studies of ultra-high energy cosmic rays, as well as bring new knowledge about other phenomena manifesting themselves in the atmosphere in the UV range.

astro-ph.IM↗

arXiv2021

Energy spectra of secondaries in proton-proton interactions

We compare the predictions of AAfrag for the spectra of secondary photons, neutrinos, electrons, and positrons produced in proton-proton collisions to those of the parameterisations of Kamae et al., Kelner et al., and Kafexhiu et al. We find that the differences in the normalisation of the photon energy spectra reach 20$-$50% at intermediate values of the transferred energy fraction $x$, growing up to a factor of two for $x\rightarrow\,$1, while the differences in the neutrino spectra are even larger. We argue that LHCf results on the forward production of photons favor the use of the QGSJET-II-04m model on which AAfrag is based. The differences in the normalisation have important implications in the context of multi-messenger astronomy, in particular, for the prediction of neutrino fluxes based on gamma-ray flux measurements, or regarding the inference of the cosmic ray spectrum, based on gamma-ray data. We note also that the positron-electron ratio from hadronic interactions increases with energy towards the cutoff, an effect which is missed using the average electron-positron spectrum from Kelner et al. Finally, we describe the publicly available python package aafragpy, which provides the secondary spectra of photons, neutrinos, electrons, and positrons. This package complements the AAfrag results for protons with energies above 4 GeV with previous analytical parameterizations of particle spectra for lower energy protons.

astro-ph.HE↗

arXiv2021

Sensitivity of top-of-the-mountain fluorescence telescope system for astrophysical neutrino flux above 10 PeV

Tau neutrinos with energies in the PeV-EeV range produce up-going extensive air showers (UEAS) if they interact underground close enough to the surface of the Earth. This work studies detectability of the UEAS with a system of fluorescence telescopes overlooking dark, low reflectivity, area on the ground up to the distances 20-30 km from mountain top(s). Such system could provide sensitivity sufficient for accumulation of the astrophysical neutrino signal statistics at the rate ten(s) events per year in the energy range beyond 10 PeV, thus allowing to extend the energy frontier of neutrino astronomy into 10-100 PeV range. Comparison of sensitivities of the top-of-the-mountain telescope and IceCube Generation II shows that the two approaches for neutrino detection are complementary, providing comparable performance in adjacent energy bands below and above 10 PeV. Sensitivity of the top-of-the-mountain fluorescence telescope system is also sufficient for the discovery of theoretically predicted cosmogenic neutrino signal.

astro-ph.HE↗

arXiv2021

New limit on high Galactic latitude PeV gamma-ray flux from Tibet AS-gamma data

Tibet AS-gamma collaboration has recently reported detection of gamma-rays with energies up to Peta-electronvolt from parts of the Galactic plane. We notice that the analysis of gamma-ray flux by the Tibet AS-gamma experiment also implies an upper bound on the diffuse gamma-ray flux from high Galactic latitudes(|b|>20 degrees) in the energy range between 100 TeV and 1 PeV. This bound is up to an order-of-magnitude stronger than previously derived bounds from GRAPES3, KASCADE and CASA-MIA experiments. We discuss the new TibetAS-gamma limit on high Galactic latitude gamma-ray flux in the context of possible mechanisms of multi-messenger (gamma-ray and neutrino) emission from nearby cosmic ray sources, dark matter decays and large scale cosmic ray halo of the Milky Way.

astro-ph.HE↗

arXiv2021

The POEMMA (Probe of Extreme Multi-Messenger Astrophysics) Observatory

The Probe Of Extreme Multi-Messenger Astrophysics (POEMMA) is designed to accurately observe ultra-high-energy cosmic rays (UHECRs) and cosmic neutrinos from space with sensitivity over the full celestial sky. POEMMA will observe the extensive air showers (EASs) from UHECRs and UHE neutrinos above 20 EeV via air fluorescence. Additionally, POEMMA will observe the Cherenkov signal from upward-moving EASs induced by Earth-interacting tau neutrinos above 20 PeV. The POEMMA spacecraft are designed to quickly re-orientate to follow up transient neutrino sources and obtain unparalleled neutrino flux sensitivity. Developed as a NASA Astrophysics Probe-class mission, POEMMA consists of two identical satellites flying in loose formation in 525 km altitude orbits. Each POEMMA instrument incorporates a wide field-of-view (45$^\circ$) Schmidt telescope with over 6 m$^2$ of collecting area. The hybrid focal surface of each telescope includes a fast (1~$μ$s) near-ultraviolet camera for EAS fluorescence observations and an ultrafast (10~ns) optical camera for Cherenkov EAS observations. In a 5-year mission, POEMMA will provide measurements that open new multi-messenger windows onto the most energetic events in the universe, enabling the study of new astrophysics and particle physics at these otherwise inaccessible energies.

astro-ph.IM↗

arXiv2021

NANOGrav signal from MHD turbulence at QCD phase transition in the early universe

The NANOGrav collaboration has recently reported evidence for the existence of a stochastic gravitational wave background in the 1-100 nHz frequency range. We argue that such background could have been produced by magneto-hydrodynamic (MHD) turbulence at the QCD scale. From the NANOGrav measurement one can infer the magnetic field parameters: comoving field strength close to microGauss and a correlation length close to 10\% of the Hubble radius at the QCD phase transition epoch. We point out that the turbulent decay of a non-helical magnetic field with such parameters leads to a magnetic field at the recombination epoch, which would be sufficiently strong to provide a solution to the Hubble tension problem, as recently proposed. We also show that the MHD turbulence interpretation of the NANOGrav signal can be tested via measurements of the relic magnetic field in the voids of the large scale structure, with gamma-ray telescopes like CTA.

astro-ph.CO↗

arXiv2021

An online data analysis system of INTEGRAL telescope

During more than 17 years of operation in space INTEGRAL telescope has accumulated large data set that contains records of hard X-ray and soft gamma-ray astronomical sources. These data can be re-used in the context of multi-wavelength or multi-messenger studies of astronomical sources and have to be preserved on long time scales. We present a scientific validation of an interactive online INTEGRAL data analysis system for multi-wavelength studies of hard X-ray and soft gamma-ray sources. The online data analysis system generates publication-quality high-level data products: sky images, spectra and light-curves in response to user queries that define analysis parameters, such as source position, time and energy interval and binning. The data products can be requested via a web browser interface or via Application Programming Interface (API) available as a Python package. The analysis workflow organized to preserve and re-use various intermediate analysis products, ensuring that frequently requested results are available without delay. The platform can be deployed in any compatible infrastructure. We report the functionalities and performance of the online data analysis system by reproducing the benchmark INTEGRAL results on different types of sources, including bright steady and transient Galactic sources, and bright and weak variable extra-galactic sources. We compare the results obtained with the online data analysis system with previously published results on these sources. We consider the INTEGRAL online data analysis as a demonstrator of more general web-based "data analysis as a service" approach that provides a promising solution for preservation and maintenance of data analysis tools of astronomical telescopes on (multi)decade long time scales and facilitates combination of data in multi-wavelength and multi-messenger studies of astronomical sources.

astro-ph.IM↗

arXiv2021

Possibility of measurement of cosmic ray electron spectrum up to 100 TeV with two-layer water Cherenkov detector array

Measurements of cosmic ray electron+positron spectrum above 10 TeV with ground-based experiments is challenging because of the difficulty of rejection of hadronic extensive air shower background. We study the efficiency of rejection of the hadronic background with water Cherenkov detector array supplemented by muon detection layer. We show that addition of a continuous muon detection layer to the experimental setup allows to achieve a ~ 1e-5 rejection factor for hadronic background at 10 TeV and enables measurement of electron spectrum in 10-100 TeV energy range. We show that measurements of electron spectrum in this energy range do not require a high-altitude experiment and can be done with a sea-level detector.

astro-ph.HE↗

arXiv2020

Sensitivity reach of gamma-ray measurements for strong cosmological magnetic fields

A primordial magnetic field with the strength in the 1-10 pG range can resolve the tension between different measurements of the Hubble constant and provide an explanation for the excess opacity in the 21 cm line at redshift $15<z<20$, if it is present during the recombination and reionization epochs. This field can also survive in the voids of the large-scale Structure in the present day universe. We study the sensitivity reach of the gamma-ray technique for measurement of such relatively strong cosmological magnetic field using deep exposure(s) of the nearest hard spectrum blazar(s) with CTA telescopes. We show that the gamma-ray measurement method can sense the primordial magnetic field with a strength of up to $10^{-11}$~G. Combination of the cosmic microwave background and gamma-ray constraints can thus sense the full range of possible cosmological magnetic fields to confirm or rule out their relevance to the problem of the origin of cosmic magnetic fields, as well as their influence on recombination and reionization epochs.

astro-ph.CO↗

arXiv2020

The INTEGRAL view of the pulsating hard X-ray sky: from accreting and transitional millisecond pulsars to rotation-powered pulsars and magnetars

In the last 25 years, a new generation of X-ray satellites imparted a significant leap forward in our knowledge of X-ray pulsars. The discovery of accreting and transitional millisecond pulsars proved that disk accretion can spin up a neutron star to a very high rotation speed. The detection of MeV-GeV pulsed emission from a few hundreds of rotation-powered pulsars probed particle acceleration in the outer magnetosphere, or even beyond. Also, a population of two dozens of magnetars has emerged. INTEGRAL played a central role to achieve these results by providing instruments with high temporal resolution up to the hard X-ray/soft gamma-ray band and a large field of view imager with good angular resolution to spot hard X-ray transients. In this article, we review the main contributions by INTEGRAL to our understanding of the pulsating hard X-ray sky, such as the discovery and characterization of several accreting and transitional millisecond pulsars, the generation of the first catalog of hard X-ray/soft gamma-ray rotation-powered pulsars, the detection of polarization in the hard X-ray emission from the Crab pulsar, and the discovery of persistent hard X-ray emission from several magnetars.

astro-ph.HE↗