• Liang Chen

      Articles written in Journal of Astrophysics and Astronomy

    • X-ray Radiation Mechanisms and the Beaming Effect of Hot Spots and Knots in AGN Jets

      Jin Zhang Jin-Ming Bai Liang Chen Enwei Liang

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      The observed broadband spectral energy distributions (SEDs) of 22 hot spots and 45 knots are modelled with single-zone lepton models. Considering the sources at rest, the X-rays of some hot spots can be explained by the SSC model with magnetic field being consistent with the equipartition magnetic field in magnitude of order 1, but at the same time an unreasonably low magnetic field is required to model the X-rays for all knots. When considering the relativistic bulk motion of the sources, the IC/CMB model well explains the X-ray emission for most of them under the equipartition condition. We show that the ratio of observational luminosity 𝑅𝐿 is tentatively correlated with the co-moving equipartition magnetic field 𝐵'eq and the beaming factor 𝛿. These facts suggest that the observational differences of the X-rays from the knots and hot spots may be mainly due to the differences in the Doppler boosting effect and the co-moving magnetic field of the two kinds of source.

    • Blazar Sequence in Fermi Era

      Liang Chen

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      In this paper, we review the latest research results on the topic of blazar sequence. It seems that the blazar sequence is phenomenally ruled out, while the theoretical blazar sequence still holds. We point out that black hole mass is a dominated parameter accounting for high-power-high-synchrotron-peaked and low-power-low-sychrotron-peaked blazars. Because most blazars have similar size of emission region, theoretical blazar sequence implies that the break of Spectral Energy Distribution (SED) is a cooling break in nature.

    • Multi-Wavelength Variability Properties of Fermi Blazar S5 0716+714

      N. H. Liao J. M. Bai H. T. Liu S. S. Weng Liang Chen F. Li

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      The multi-wavelength variability properties of blazar S5 0716 + 714 are reported. We construct multi-wavelength light curves of radio, optical, X-ray and 𝛾-ray including our optical observation at Yunnan Observatories. In all the bands, the light curves show intense variabilities. The variability amplitudes in 𝛾-ray and optical bands are larger than those in the hard X-ray and radio bands. The characteristic variability timescales at 14.5 GHz, optical, X-ray, and 𝛾-ray bands are comparable. The variations of the hard X-ray and 14.5GHz emissions are correlated with zero lag, and so are the V band and 𝛾-ray variations. The multi-wavelength variability behaviours can be naturally explained by the classic leptonic model. We model the average SED of S5 0716 + 714 by leptonic model. The SSC+ERC model using the external seed photons from hot dust or Broad Line Region (BLR) emission is probably favourable avoiding the extreme input parameters from the pure SSC model.

  • Journal of Astrophysics and Astronomy | News

    • 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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