arXiv subjects

Nino Chkheidze

Publications and source records attributed to Nino Chkheidze.

12 recordsLinked to original sources

arXiv2018

Emission of extremely bright gamma-ray pulsar in the Large Magellanic Cloud

In the present paper a theoretical interpretation of observational characteristics of the pulsar PSR J0540-6919 is suggested. In particular, we provide a theoretical model explaining the presence of two peaks in the radio domain and the brooding of these peaks at higher frequencies. The model also explains the pulse-phase coincidence of emission peaks at different frequencies and shows the physical, 'genetic' connection between the radio remission at frequencies of the order of GHz with gamma-ray emission up to GeV energies.

astro-ph.HE↗

arXiv2018

Energy accumulation mechanism in pulsar magnetospheric plasma eigen-waves and formation of Giant Radio Pulses

In the present work we consider energy accumulation mechanism in relativistic electron-positron plasma in the magnetosphere of pulsars. Waves propagating almost across the magnetic field lines are generated that accumulate the energy of plasma particles, as the waves stay significantly long in the resonance region. The accumulated energy is transmitted in the parallel direction of the magnetic field lines as soon as the non-linear plasma processes start to operate. It is suggested that exit of the accumulated energy via waves propagating along the magnetic field lines matching the viewing angle of the observer produces giant pulses. It is shown that these waves come in the radio domain, explaining the Giant Radio Pulse phenomenon.

astro-ph.HE↗

arXiv2014

Extremely efficient Zevatron in rotating AGN magnetospheres

A novel model of particle acceleration in the magnetospheres of rotating active galactic nuclei (AGN) is constructed.The particle energies may be boosted up to $10^{21}$eV in a two step mechanism: In the first stage, the Langmuir waves are centrifugally excited and amplified by means of a parametric process that efficiently pumps rotational energy to excite electrostatic fields. In the second stage, the electrostatic energy is transferred to particle kinetic energy via Landau damping made possible by rapid "Langmuir collapse". The time-scale for parametric pumping of Langmuir waves turns out to be small compared to the kinematic time-scale, indicating high efficiency of the first process. The second process of "Langmuir collapse" - the creation of caverns or low density regions - also happens rapidly for the characteristic parameters of the AGN magnetosphere. The Langmuir collapse creates appropriate conditions for transferring electric energy to boost up already high particle energies to much higher values. It is further shown that various energy loss mechanism are relatively weak, and do not impose any significant constraints on maximum achievable energies.

astro-ph.HE↗

arXiv2014

On high frequency Cherenkov-type radiation in pulsar magnetospheric electron-positron plasma

Emission process of a charged particle propagating in a medium with a curved magnetic field is considered. This mechanism combines features of conventional Cherenkov and curvature emission. Thus, presence of a medium with the index of refraction larger than the unity is essential for the emission. In the present paper the generation of high frequency radiation by the mentioned mechanism is considered. The generated waves are vacuum-like electromagnetic waves and may leave the medium directly. Consequently, this emission mechanism may be important for the problem of pulsar X-ray and gamma-ray emission generation.

astro-ph.HE↗

arXiv2014

On the possible mechanism to form the radio emission spectrum of the Crab pulsar

In the present paper a self-consistent theory, explaining shape of the observed phase-averaged radio spectrum in the frequency range from 100MHz to 10GHz is presented. The radio waves are assumed to be generated near the light cylinder through the cyclotron resonance. The cyclotron instability provides excitement of the electron-positron plasma eigen-waves, which come in radio domain when the resonant particles are the most energetic primary beam electrons. It is widely accepted that the distribution function of relativistic particles is one-dimensional at the pulsar surface. The generated waves react back on the resonant particles causing their diffusion in the perpendicular direction to the magnetic field and violating the one-dimensionality, which switches on the synchrotron radiation process. The synchrotron emission of the beam electrons provides generation of high-energy $γ$-rays simultaneously with the radio emission, that explains the observed pulse phase-coincidence in these energy domains. The theory provides a power-law radio spectrum with the spectral index equal to $3.7$, coming in agreement with the observations.

astro-ph.HE↗

arXiv2013

Nonthermal emission model of isolated X-ray pulsar RX J0420.0-5022

In the present paper an alternative theoretical interpretation to the generally assumed thermal emission models of the observed X-ray spectrum of isolated pulsar RX J0420.0-5022 is presented. It is well known that the distribution function of relativistic particles is one-dimensional at the pulsar surface. However, cyclotron instability causes an appearance of transverse momenta of relativistic electrons, which as a result, start to radiate in the synchrotron regime. On the basis of the Vlasov's kinetic equation we study the process of the quasi-linear diffusion (QLD) developed by means of the cyclotron instability. This mechanism provides generation of optical and X-ray emission on the light cylinder lengthscales. The analysis of the three archival XMM-Newton observations of RX J0420.0-5022 is performed. Considering a different approach of the synchrotron emission theory, the spectral energy distribution is obtained that is in a good agreement with the observational data. A fit to the X-ray spectrum is performed using both the present synchrotron emission model spectrum absorbed by cold interstellar matter and generally assumed absorbed black-body model.

astro-ph.HE↗

arXiv2013

Ultra High Energy Electrons Powered by Pulsar Rotation

A new mechanism of particle acceleration to ultra high energies, driven by the rotational slow down of a pulsar (Crab pulsar, for example), is explored. The rotation, through the time dependent centrifugal force, can very efficiently excite unstable Langmuir waves in the e-p plasma of the star magnetosphere via a parametric process. These waves, then, Landau damp on electrons accelerating them in the process. The net transfer of energy is optimal when the wave growth and the Landau damping times are comparable and are both very short compared to the star rotation time. We show, by detailed calculations, that these are precisely the conditions for the parameters of the Crab pulsar. This highly efficient route for energy transfer allows the electrons in the primary beam to be catapulted to multiple TeV ($\sim 100$ TeV) and even PeV energy domain. It is expected that the proposed mechanism may, partially, unravel the puzzle of the origin of ultra high energy cosmic ray electrons.

astro-ph.HE↗

arXiv2012

Synchrotron emission driven by the Cherenkov-drift instability in active galactic nuclei

In the present paper we study generation of the synchrotron emission by means of the feedback of Cherenkov drift waves on the particle distribution via the diffusion process. It is shown that despite the efficient synchrotron losses the excited Cherenkov drift instability leads to the quasi-linear diffusion (QLD), effect of which is balanced by dissipation factors and as a result the pitch angles are prevented from damping, maintaining the corresponding synchrotron emission. The model is analyzed for a wide range of physical parameters and it is shown that the mechanism of QLD guarantees the generation of electromagnetic radiation from soft $X$-rays up to soft $γ$-rays, strongly correlated with Cherenkov drift emission ranging from IR up to UV energy domains.

astro-ph.HE↗

arXiv2012

On the mechanism of the pulsed high energy emission from the pulsar PSR B1509-58

We investigate the high-energy (HE) ($<1$GeV) emission from the pulsar PSR B1509-58 and its relation to the radio emission in the 1.4GHz frequency band. The role of the quasi-linear diffusion in producing the pulsed HE radiation is investigated. We show that by means of the cyclotron instability the relatively low frequency waves excite, which due to the diffusion process influence the particle distribution function and switch on the synchrotron emission mechanism. We argue that the coincidence of HE main peak and the radio pulse is a direct consequence of the fact that the high and low frequency radiation is produced simultaneously in a local area of the pulsar magnetosphere. In the paper we also consider the absence of the radio counter pulse and explain this fact.

astro-ph.HE↗

arXiv2012

On the spectrum of the pulsed gamma-ray emission from 10MeV to 400GeV of the Crab pulsar

In the present paper a self-consistent theory, interpreting the VERITAS observations of the very high energy pulsed emission from the Crab pulsar is considered. The photon spectrum between 10MeV and 400GeV can be described by two power-law functions with the spectral indexes equal to 2 and 3.8. The source of the pulsed emission above 10MeV is assumed to be the synchrotron radiation, which is generated near the light cylinder during the quasi-linear stage of the cyclotron instability. The emitting particles are the primary beam electrons with the Lorentz factors up to $10^{9}$. Such high energies by beam particles is supposed to be reached due to Landau damping of the centrifugally induced Langmuir waves. This mechanism provides simultaneous generation of low (radio) and high energy (10MeV-400GeV) emission on the light cylinder scales, in one location of the pulsar magnetosphere.

astro-ph.HE↗

arXiv2010

The plasma emission model of RBS1774

In the present paper we construct a self-consistent theory, interpreting the observational properties of RBS1774. It is well known that the distribution function of relativistic particles is one-dimensional at the pulsar surface. However, cyclotron instability causes an appearance of transverse momenta of relativistic electrons, which as a result, start to radiate in the synchrotron regime. We study the process of the quasi-linear diffusion developed by means of the cyclotron instability on the basis of the Vlasov's kinetic equation. This mechanism provides generation of measured optical and X-ray emission on the light cylinder lengthscales. A different approach of the synchrotron theory is considered, giving the spectral energy distribution that is in a good agreement with the XMM-Newton observational data. We also provide the possible explanation of the spectral feature at 0.7keV, in the framework of the model.

astro-ph.SR↗

arXiv2009

On the emission polarization of RX J1856.5-3754

The polarization properties of RX J1856.5-3754 are investigated, based on the plasma emission model presented in previous works. It is shown that if the emission of this source is generated by the synchrotron mechanism, the X-ray and the optical emission are linearly polarized and the corresponding degrees of linear polarization are calculated. The measurement of the polarization patterns of this source appears to be most reliable way, to make clear its real emission nature.

astro-ph.SR↗