• Jin Zhang

      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.

    • Statistical Properties of Gamma-Ray Burst Host Galaxies

      Jie-Min Chen Jin Zhang Lan-Wei Jia En-Wei Liang

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      A statistical analysis of gamma-ray burst host galaxies is presented and a clear metallicity-stellar mass relation is found in our sample. A trend that a more massive host galaxy tends to have a higher star-formation rate is also found. No correlation is found between 𝐴V and 𝑁H. GRB host galaxies at a higher redshift also tend to have a higher star formation rate, however, even in the same redshift, the star formation rate may vary for three orders of magnitude.

    • Spectral Variation of NLS1 Galaxy PMN J0948+0022

      X. N. Sun Jin Zhang Y. Lu E. W. Liang S. N. Zhang

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      Four well-sampled Spectral Energy Distributions (SEDs) of PMN J0948+0022 are fitted with the syn+SSC+EC model to derive the physical parameters of its jets and to investigate the spectral variations of its SEDs. A tentative correlation between the peak luminosity (𝐿c) and peak frequency (𝑣c) of its inverse Compton (IC) bump is found in both the observer and co-moving frames, indicating that the variations of luminosity are accompanied by the spectral shift. A correlation between 𝐿cs and 𝛿 is found, and thus the magnification of external photon field by the bulk motion of the radiation regions is an essential reason for the spectral variation since, IC bump of PMN J0948+0022 is dominated by the EC process.

  • 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.

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