• Y. G. Zheng

      Articles written in Journal of Astrophysics and Astronomy

    • Multi-Wavelength Variability in PKS 2155-304

      Y. G. Zheng L. Zhang X. Zhang H. J. Ma

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      We study multi-wavelength variability in BL Lacertae object PKS 2155-304 in the frame of the time dependent one-zone synchrotron self-Compton (SSC) model, where stochastic particle acceleration is taken into account. In this model, a homogeneously and isotropically spherical structure is assumed, the Fokker–Planck type equation which describes the evolution of the particles energy is numerically solved, and the synchrotron and self-Compton components from the spherical blob are calculated. Our results can reproduce observed spectra energy distribution (SED) and give definite predictions for the flux and spectral variability of PKS 2155-304.We find that particle injection rate, magnetic field and Doppler factor in the acceleration zone are important parameters for explaining its flaring behaviour.

    • Fractal Property in the Light Curve of BL Lac Object S5 0716+714

      J. W. Ou Y. G. Zheng

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      In this paper, we compile the historical R-band data of S5 0716+714 from literature and obtain its fractal dimension by using a fractal method and then simulate the data with the Weierstrass–Mandelbrot (W–M) function. It is considered that the light curve has a fractal property.

    • 𝛾-Ray Emission from the Extreme Blazar 1ES 0229+200

      J. Li T. Kang Y. G. Zheng

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      Based on the traditional Synchrotron Self-Compton (SSC) model, we consider a secondary γ -ray emission component to an extreme blazar 1ES 0229 + 200 for the multiwavelength radiation. By assuming a suitable electron spectra and Inter-Galactic Magnetic Field (IGMF), we obtained excellent fits to observed spectra of the source. This indicated that the observed excess GeV 𝛾-rays emission can be explained by secondary 𝛾-rays produced through inverse Compton scattering of 𝑒± pairs against Cosmic Microwave Background (CMB) photons.

    • Delta-function Approximation SSC Model in 3C 273

      S. J. Kang Y. G. Zheng Q. Wu

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      We obtain an approximate analytical solution using 𝛿 approximate calculation on the traditional one-zone synchrotron self-Compton (SSC) model. In this model, we describe the electron energy distribution by a broken power-law function with a sharp cut-off, and non-thermal photons are produced by both synchrotron and inverse Compton scattering of synchrotron photons. We calculate the radiation energy spectrum of electrons by the 𝛿 function. We apply this model to the multi-wavelength Spectral Energy Distributions (SED) of the 3C 273 in different states, and obtain excellent fits to the observed spectra of this source.

    • Power Spectrum Density of Stochastic Oscillating Accretion Disk

      G. B. Long J. W. Ou Y. G. Zheng

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      In this paper, we employ a stochastic oscillating accretion disk model for the power spectral index and variability of BL Lac object S5 0716+714. In the model, we assume that there is a relativistic oscillation of thin accretion disks and it interacts with an external thermal bath through a friction force and a random force. We simulate the light curve and the power spectrum density (PSD) at (i) over-damped, (ii) critically damped and (iii) under-damped cases, respectively. Our results show that the simulated PSD curves depend on the intrinsic property of the accretion disk, and it could be produced in a wide interval ranging from 0.94 to 2.05 by changing the friction coefficient in a stochastic oscillating accretion disk model. We argue that accretion disk stochastic oscillating could be a possible interpretation for observed PSD variability.

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    • Continuous Article Publication

      Posted on January 27, 2016

      Since January 2016, the Journal of Astrophysics and Astronomy has moved to Continuous Article Publishing (CAP) mode. This means that each accepted article is being published immediately online with DOI and article citation ID with starting page number 1. Articles are also visible in Web of Science immediately. All these have helped shorten the publication time and have improved the visibility of the articles.

    • Editorial Note on Continuous Article Publication

      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

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