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V N Zirakashvili - One of the best experts on this subject based on the ideXlab platform.
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Cosmic Rays and Nonthermal Radiation in Middle-Aged Supernova Remnants
Astronomy Letters, 2018Co-Authors: V N Zirakashvili, V. S. PtuskinAbstract:A nonlinear model of cosmic-ray acceleration at the shock fronts in the supernova remnants W28, W44, and IC433 is investigated. The hydrodynamic evolution of a supernova remnant, including the shock modification by the pressure of accelerated particles and the streaming instability of particles upstream of the shock propagating in a partially ionized interstellar gas, is modeled. The electromagnetic Radiation generated by accelerated particles is calculated and compared with observations in a wide range of photon energies.
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Nonthermal Radiation of young supernova remnants: the case of Cas A
The Astrophysical Journal, 2014Co-Authors: V N Zirakashvili, Felix Aharonian, Ruizhi Yang, Ema Ona-wilhelmi, Richard J. TuffsAbstract:The processes responsible for the broadband Radiation of the young supernova remnant Cas A are explored by using a new code that is designed for a detailed treatment of the diffusive shock acceleration of particles in the nonlinear regime. The model is based on spherically symmetric hydrodynamic equations complemented with transport equations for relativistic particles. Electrons, protons, and the oxygen ions accelerated by forward and reverse shocks are included in the numerical calculations. We show that the available multi-wavelength observations in the radio, X-ray, and gamma-ray bands can be best explained by invoking particle acceleration by both forward and reversed shocks. Although the TeV gamma-ray observations can be interpreted by interactions of both accelerated electrons and protons/ions, the measurements by Fermi Large Area Telescope at energies below 1 GeV give a tentative preference to the hadronic origin of gamma-rays. Then, the acceleration efficiency in this source, despite the previous claims, should be very high; 25% of the explosion energy (or approximately 3 × 10{sup 50} erg) should already be converted to cosmic rays, mainly by the forward shock. At the same time, the model calculations do not provide extension of the maximum energy of accelerated protons beyond 100 TeV. Inmore » this model, the acceleration of electrons is dominated by the reverse shock; the required 10{sup 48} erg can be achieved under the assumption that the injection of electrons (positrons) is supported by the radioactive decay of {sup 44}Ti.« less
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Nonthermal Radiation of young supernova remnants the case of cas a
arXiv: High Energy Astrophysical Phenomena, 2013Co-Authors: V N Zirakashvili, Felix Aharonian, Ruizhi Yang, Ema Onawilhelmi, Richard J. TuffsAbstract:The processes responsible for the broad-band Radiation of the young supernova remnant Cas A are explored using a new code which is designed for a detailed treatment of the diffusive shock acceleration of particles in nonlinear regime. The model is based on spherically symmetric hydrodynamic equations complemented with transport equations for relativistic particles. Electrons, protons and the oxygen ions accelerated by forward and reverse shocks are included in the numerical calculations. We show that the available multi-wavelength observations in the radio, X-ray and gamma-ray bands can be best explained by invoking particle acceleration by both forward and reversed shocks. Although the TeV gamma-ray observations can be interpreted by interactions of both accelerated electrons and protons/ions, the measurements by Fermi LAT at energies below 1 GeV give a tentative preference to the hadronic origin of gamma-rays. Then, the acceleration efficiency in this source, despite the previous claims, should be very high; 25% of the explosion energy (or approximately $3\cdot 10^{50}$ erg) should already be converted to cosmic rays, mainly by the forward shock. At the same time, the model calculations do not provide extension of the maximum energy of accelerated protons beyond 100 TeV. In this model, the acceleration of electrons is dominated by the reverse shock; the required $10^{48}$ erg can be achieved under the assumption that the injection of electrons (positrons) is supported by the radioactive decay of $^{44}$Ti.
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Particle acceleration and Nonthermal Radiation in supernova remnants
Journal of Physics: Conference Series, 2013Co-Authors: V N ZirakashviliAbstract:Cosmic ray acceleration and magnetic amplification in shell-type supernova remnants is shortly reviewed. The results on the modeling of broadband electromagnetic emission from supernova remnants are presented and compared with observations.
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Nonthermal Radiation OF YOUNG SUPERNOVA REMNANTS: THE CASE OF RX J1713.7–3946
The Astrophysical Journal, 2009Co-Authors: V N Zirakashvili, Felix AharonianAbstract:A new numerical code, designed for the detailed numerical treatment of nonlinear diffusive shock acceleration, is used for the modeling of particle acceleration and Radiation in young supernova remnants (SNRs). The model is based on spherically symmetric hydrodynamic equations complemented with transport equations for relativistic particles. For the first time, the acceleration of electrons and protons by both forward and reverse shocks is studied through detailed numerical calculations. We model the energy spectra and spatial distributions of Nonthermal emission of the young SNR RX J1713.7–3946 and compare the calculations with the spectral and morphological properties of this object obtained in broad energy band from radio to very high-energy gamma rays. We discuss the advantages and shortcomings of the so-called hadronic and leptonic models, which assume that the observed TeV gamma-ray emission is produced by accelerated protons and electrons, respectively. We discuss also a "composite" scenario when the gamma-ray flux from the main parts of the shell has inverse Compton origin, but with a non-negligible contribution of hadronic origin from dense clouds interacting with the shell.
V V Usov - One of the best experts on this subject based on the ideXlab platform.
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on the nature of Nonthermal Radiation from cosmological γ ray bursters
Gamma‐ray bursts: Second workshop, 2008Co-Authors: V V UsovAbstract:Relativistic electron‐positron winds with strong magnetic fields are considered as a source of Radiation for cosmological γ‐ray bursters. Such a wind is generated by a millisecond pulsar with a very strong magnetic field. It is shown that at the distance of ∼1013 cm from the pulsar the magnetohydrodynamic approximation for the pulsar wind is broken, and intense electromagnetic waves may be generated. The frequency of these waves is equal to the frequency of the pulsar rotation. Outflowing particles are accelerated in the field of intense electromagnetic waves to Lorentz factors of the order of 106 and generate Nonthermal synchro‐Compton Radiation. The typical energy of Nonthermal photons is ∼1 MeV. A high‐energy tail of the γ‐ray spectrum may be up to ∼104 MeV. Baryonic matter is ejected occasionally from the pulsar magnetosphere. The baryonic matter ejection and subsequent suppression of the γ‐ray emission may be responsible for the time structure of γ‐ray bursts.
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Nonthermal Radiation of cosmological gamma ray bursters
The Astrophysical Journal, 2000Co-Authors: M V Smolsky, V V UsovAbstract:We use 1.5 dimensional particle-in-cell plasma simulations to study the interaction of a relativistic, strongly magnetized wind with an ambient medium. Such an interaction is a plausible mechanism that leads to generation of cosmological γ-ray bursts. We confirm the idea of Meszaros & Rees that an essential part (about 20%) of the energy that is lost by the wind in the process of its deceleration may be transferred to high-energy electrons and then to high-frequency (X-ray and γ-ray) emission. We show that in the wind frame the spectrum of electrons that are accelerated at the wind front and move ahead of the front is nearly a two-dimensional relativistic Maxwellian with a relativistic temperature T = mec2ΓT/k 6 × 109ΓT K, where ΓT is equal to 200Γ0, with the accuracy of ~20%, and Γ0 is the Lorentz factor of the wind, Γ0 102 for winds outflowing from cosmological γ-ray bursters. Our simulations point to an existence of a high-energy tail of accelerated electrons with a Lorentz factor of more than ~700Γ0. Large-amplitude electromagnetic waves are generated by the oscillating currents at the wind front. The mean field of these waves ahead of the wind front is an order of magnitude less than the magnetic field of the wind. High-energy electrons that are accelerated at the wind front and injected into the region ahead of the front generate synchro-Compton Radiation in the fields of large-amplitude electromagnetic waves. This Radiation closely resembles synchrotron Radiation and can reproduce the Nonthermal Radiation of γ-ray bursts observed in the Ginga and BATSE ranges (from a few keV to a few MeV). Synchrotron photons that are generated in the vicinity of the wind front may be responsible for the Radiation of γ-ray bursts in the EGRET energy range above a few ten MeV. The spectrum of γ-ray bursts in high-energy γ-rays may extend, in principle, up to the maximum energy of the accelerated electrons, which is about 1013(Γ0/102)2 eV in the frame of the γ-ray burster.
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On the nature of Nonthermal Radiation from cosmological γ‐ray bursters
AIP Conference Proceedings, 1994Co-Authors: V V UsovAbstract:Relativistic electron‐positron winds with strong magnetic fields are considered as a source of Radiation for cosmological γ‐ray bursters. Such a wind is generated by a millisecond pulsar with a very strong magnetic field. It is shown that at the distance of ∼1013 cm from the pulsar the magnetohydrodynamic approximation for the pulsar wind is broken, and intense electromagnetic waves may be generated. The frequency of these waves is equal to the frequency of the pulsar rotation. Outflowing particles are accelerated in the field of intense electromagnetic waves to Lorentz factors of the order of 106 and generate Nonthermal synchro‐Compton Radiation. The typical energy of Nonthermal photons is ∼1 MeV. A high‐energy tail of the γ‐ray spectrum may be up to ∼104 MeV. Baryonic matter is ejected occasionally from the pulsar magnetosphere. The baryonic matter ejection and subsequent suppression of the γ‐ray emission may be responsible for the time structure of γ‐ray bursts.
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on the nature of Nonthermal Radiation from cosmological gamma ray bursters
Monthly Notices of the Royal Astronomical Society, 1993Co-Authors: V V UsovAbstract:Relativistic electron-positron winds with strong magnetic fields are considered as a source of Radiation for cosmological $\gamma$-ray bursters. Such a wind is generated by a millisecond pulsar with a very strong magnetic field. An electron-positron plasma near the pulsar is optically thick and in quasi-thermodynamic equilibrium. It is shown that the main part of Radiation from the pulsar wind is Nonthermal and generates in the following way. Kinetic energy which is released in the process of deceleration of the neutron star rotation transforms mainly to the magnetic field energy. The magnetic field is frozen in the outflowing plasma if the distance to the pulsar is smaller than $\sim 10^{13}$ cm. This field transfers the energy from the pulsar environment to the region outside the $\gamma$-ray photosphere of the electron-positron wind. At a distance of more than $\sim 10^{13}$ cm the magnetohydrodynamic approximation for the pulsar wind is broken, and intense electromagnetic waves are generated. The frequency of these waves is equal to the frequency of the pulsar rotation. Outflowing particles are accelerated in the field of intense electromagnetic waves to Lorentz factors of the order of $10^6$ and generate Nonthermal synchro-Compton Radiation. The typical energy of Nonthermal photons is $\sim 1$ MeV. A high-energy tail of the $\gamma$-ray spectrum may be up to $\sim 10^4$ MeV. Baryonic matter is ejected occasionally from the pulsar magnetosphere. The baryonic matter ejection and subsequent suppression of the $\gamma$-ray emission may be responsible for the time structure of $\gamma$-ray bursts.
V. S. Ptuskin - One of the best experts on this subject based on the ideXlab platform.
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Cosmic Rays and Nonthermal Radiation in Middle-Aged Supernova Remnants
Astronomy Letters, 2018Co-Authors: V N Zirakashvili, V. S. PtuskinAbstract:A nonlinear model of cosmic-ray acceleration at the shock fronts in the supernova remnants W28, W44, and IC433 is investigated. The hydrodynamic evolution of a supernova remnant, including the shock modification by the pressure of accelerated particles and the streaming instability of particles upstream of the shock propagating in a partially ionized interstellar gas, is modeled. The electromagnetic Radiation generated by accelerated particles is calculated and compared with observations in a wide range of photon energies.
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Supernova Remnants as Cosmic Accelerators
NATO Science Series, 1Co-Authors: V. S. PtuskinAbstract:Most cosmic rays are thought to be accelerated by the shocks of supernova explosions.The data on cosmic rays at the Earth and the observations of Nonthermal Radiation from supernova remnants testify that the particles are accelerated with high efficiency and in a wide range of energies.We discuss the acceleration of galactic cosmic rays in supernova remnants in a general context of the problem of cosmic-ray origin.The scenario of cosmic ray acceleration will be probably verified in full details when the data from the new generation of ground-based and space gamma-ray experiments in conjunction with new X-ray satellites will be available.
Yang Shu-zheng - One of the best experts on this subject based on the ideXlab platform.
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Discussing on the Event Horizon Surface Gravity and the Quantum Radiation of Kinnersley Black Hole Using a Tortoise Coordinate Ransformation
Journal of Sichuan University, 2006Co-Authors: Yang Shu-zhengAbstract:With a tortoise coordinate transformation,the discussing on both the event horizon surface gravity of nonstationary Kinnersley black hole and the guantum Radiation characteristics near the event horizon together with studying on the particles' moving eguation in curve spacetime shows that,not only the quantum Nonthermal Radiation but also the event horizon surface gravity and other can be considered according to Hamilton-Jacobi equation.
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Discussion on the characteristics of the quantumRadiation of unstationary and slowly-changing Reissner-Nordstr?m black hole
2005Co-Authors: Yang Shu-zhengAbstract:Taking into account the case that the mass M and charge Q of Reissner-Nordstr?m black hole varying slowly with time t, the discussion on the quant um Radiation characteristics of the black hole shows that the thermal Radiation spectrum of charged Dirac particles is connected with the black hole's evaporati on rate together with the factors M(t), Q(t) etc. changing with time, and that the maximum energy of the quantum Nonthermal Radiation of nonstationary and slowly-changing Reissner-Nordstr?m black hole is equal to the chemical potential in the quantum thermal Radiation spectrum.
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Research on the Horizon Surface Gravity and the QuatumNonthermal Radiation of Nonstationary Kerr Black Holeby Using a New Tortoise Coordinate Transformation
Journal of Xihua Teachers College, 2004Co-Authors: Yang Shu-zhengAbstract:Hamilton-Jacobi equation in the spacetime of nonstationary Kerr black hole is studied by using a new tortoise coordinate transformation.It shows that the Hamilton-Jacobi equation can discuss not only the Nonthermal Radiation,but also the surface gravity of the black hole.
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The quantum Nonthermal effect of a nonstationary Kerr-Newman black hole and the average range of the effective particles
Chinese Physics, 2002Co-Authors: Yang Shu-zheng, Lin Li-binAbstract:We have found that the Nonthermal Radiation of a nonstationary Kerr-Newman black hole is affected by interstellar materials. In particular, the interstellar gas deeply influences the average range of Nonthermal Radiation particles, while the average range depends on the maximum energy of the Radiation and the energy extent of the Radiation.
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Research on The Range of The Nonthermal Radiation Particles from Charged Accelerational-motion Black Hole
Journal of Sichuan University, 2002Co-Authors: Yang Shu-zhengAbstract:Authors have researched the relationship between the energy extent of the Nonthermal Radiation particle from charged accelerational-motion black hole and its Radiation direction. The result is that Radiation particles' average range varies with its direction.
Hyesung Kang - One of the best experts on this subject based on the ideXlab platform.
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Nonthermal Radiation from relativistic electrons accelerated at spherically expanding shocks
arXiv: High Energy Astrophysical Phenomena, 2014Co-Authors: Hyesung KangAbstract:We study the evolution of the energy spectrum of cosmic-ray electrons accelerated at spherically expanding shocks with low Mach numbers and the ensuing spectral signatures imprinted in radio synchrotron emission. Time-dependent simulations of diffusive shock acceleration (DSA) of electrons in the test-particle limit have been performed for spherical shocks with parameters relevant for typical shocks in the intracluster medium. The electron and Radiation spectra at the shock location can be described properly by the test-particle DSA predictions with instantaneous shock parameters. However, the volume integrated spectra of both electrons and Radiation deviate significantly from the test-particle power-laws, because the shock compression ratio and the flux of injected electrons at the shock gradually decrease as the shock slows down in time.So one needs to be cautious about interpreting observed radio spectra of evolving shocks based on simple DSA models in the test-particle regime.
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Nonthermal Radiation from Supernova Remnants: Effects of Magnetic Field Amplification and Particle Escape
The Astrophysical Journal, 2013Co-Authors: Hyesung Kang, Thomas W Jones, Paul P. EdmonAbstract:We explore nonlinear effects of wave-particle interactions on the diffusive shock acceleration (DSA) process in Type Ia-like supernova remnant (SNR) blast waves by implementing phenomenological models for magnetic field amplification (MFA), Alfvenic drift, and particle escape in time-dependent numerical simulations of nonlinear DSA. For typical SNR parameters, the cosmic-ray (CR) protons can be accelerated to PeV energies only if the region of amplified field ahead of the shock is extensive enough to contain the diffusion lengths of the particles of interest. Even with the help of Alfvenic drift, it remains somewhat challenging to construct a nonlinear DSA model for SNRs in which of the order of 10% of the supernova explosion energy is converted into CR energy and the magnetic field is amplified by a factor of 10 or so in the shock precursor, while, at the same time, the energy spectrum of PeV protons is steeper than E –2. To explore the influence of these physical effects on observed SNR emission, we also compute the resulting radio-to-gamma-ray spectra. Nonthermal emission spectra, especially in X-ray and gamma-ray bands, depend on the time-dependent evolution of the CR injection process, MFA, and particle escape, as well as the shock dynamic evolution. This result comes from the fact that the high-energy end of the CR spectrum is composed of particles that are injected in the very early stages of the blast wave evolution. Thus, it is crucial to better understand the plasma wave-particle interactions associated with collisionless shocks in detailed modeling of Nonthermal Radiation from SNRs.
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Nonthermal Radiation from Supernova Remnant Shocks
Journal of Astronomy and Space Sciences, 2013Co-Authors: Hyesung KangAbstract:Most of high energy cosmic rays (CRs) are thought to be produced by diffusive shock acceleration (DSA) at supernova remnants (SNRs) within the Galaxy. Fortunately, Nonthermal emissions from CR protons and electrons can provide direct observational evidence for such a model and place strong constraints on the complex nonlinear plasma processes in DSA theory. In this study we calculate the energy spectra of CR protons and electrons in Type Ia SNRs, using time-dependent DSA simulations that incorporate phenomenological models for some wave-particle interactions. We demonstrate that the time-dependent evolution of the self-amplified magnetic fields, Alfvnic drift, and escape of the highest energy particles affect the energy spectra of accelerated protons and electrons, and so resulting Nonthermal Radiation spectrum. Especially, the spectral cutoffs in X-ray and -ray emission spectra are regulated by the evolution of the highest energy particles, which are injected at the early phase of SNRs. Thus detailed understandings of nonlinear wave-particle interactions and time-dependent DSA simulations of SNRs are crucial in testing the SNR hypothesis for the origin of Galactic cosmic rays.
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Nonthermal Radiation from supernova remnants effects of magnetic field amplification and particle escape
arXiv: High Energy Astrophysical Phenomena, 2013Co-Authors: Hyesung Kang, T W Jones, Paul EdmonAbstract:We explore nonlinear effects of wave-particle interactions on the diffusive shock acceleration (DSA) process in Type Ia-like, SNR blast waves, by implementing phenomenological models for magnetic field amplification, Alfv'enic drift, and particle escape in time-dependent numerical simulations of nonlinear DSA. For typical SNR parameters the CR protons can be accelerated to PeV energies only if the region of amplified field ahead of the shock is extensive enough to contain the diffusion lengths of the particles of interest. Even with the help of Alfv'enic drift, it remains somewhat challenging to construct a nonlinear DSA model for SNRs in which order of 10 % of the supernova explosion energy is converted to the CR energy and the magnetic field is amplified by a factor of 10 or so in the shock precursor, while, at the same time, the energy spectrum of PeV protons is steeper than E^{-2}. To explore the influence of these physical effects on observed SNR emissions, we also compute resulting radio-to-gamma-ray spectra. Nonthermal emission spectra, especially in X-ray and gamma-ray bands,depend on the time dependent evolution of CR injection process, magnetic field amplification, and particle escape, as well as the shock dynamic evolution. This result comes from the fact that the high energy end of the CR spectrum is composed of the particles that are injected in the very early stages of blast wave evolution. Thus it is crucial to understand better the plasma wave-particle interactions associated with collisionless shocks in detail modeling of Nonthermal Radiation from SNRs.
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Nonthermal Radiation from Cosmic-Ray Modified Shocks
The Astrophysical Journal, 2012Co-Authors: Hyesung Kang, Paul P. Edmon, Thomas W JonesAbstract:We calculate Nonthermal Radiation from cosmic-ray (CR) protons and electrons accelerated at CR modified plane and spherical shocks, using time-dependent, diffusive shock acceleration (DSA) simulations that include radiative losses of CR electrons. Strong non-relativistic shocks with physical parameters relevant for young supernova remnants (SNRs) are considered in both the plane-parallel and spherically symmetric geometries, and compared at times when their dynamical and CR properties are concordant. A thermal leakage injection model and a Bohm-like diffusion coefficient are adopted. After DSA energy gains balance radiative losses, the electron spectrum at the plane shock approaches a time-asymptotic spectrum with a super-exponential cutoff above the equilibrium momentum. The postshock electron spectrum cuts off at a progressively lower momentum downstream from the shock due to the energy losses. That results in the steepening of the volume integrated electron energy spectrum by one power of the particle energy. These features evolve toward lower energies in the spherical, SNR shocks. In a CR modified shock, pion decay gamma-ray emission reveals distinct signatures of nonlinear DSA due to the concave proton momentum spectrum. Although the electron momentum spectrum has a much weaker concavity, the synchrotron spectral slope at the shock may flatten by about 0.1-0.3 between radio and X-ray bands. The slope of the volume integrated emission spectrum behaves nonlinearly around the break frequency.
