• Xiong Zhang

      Articles written in Journal of Astrophysics and Astronomy

    • Multi-Wave Luminosity of High-Synchrotron-Peaked TeV BL Lacs Detected by Fermi LAT

      Dingrong Xiong Xiong Zhang Yonggang Zheng

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      We have studied the correlations between luminosities (𝐿R, 𝐿IR, 𝐿𝛾) in the radio, near-infrared and 𝛾-ray wave bands for HSP TeV BL Lacs. The results show that there are significant intrinsic correlations between 𝐿R and 𝐿𝛾 and between 𝐿IR and 𝐿𝛾 in all states (high/average/low), and suggest that for HSP TeV BL Lacs, the Synchrotron Self-Compton radiation (SSC) is the main mechanism of high energy 𝛾-ray emission, and the inverse Compton scattering of circum-nuclear dust is likely to be an important complementary mechanism.

    • Computing Optical Variable Periods of BL Lac Object S5 0716+714 with Period04 Analysis Method

      Junping Fu Xiong Zhang Dingrong Xiong

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      From a large volume of literature, we have collected effective observation of BL Lac object S5 0716+714 in the optical band, and constructed its long-term light curve from 1994 to 2006 AD. The light curve shows that S5 0716+714 is very active and exhibits very complicated non-sinusoidal variations. We used Period04 to analyse the period of light curve variation. Our results show that for S5 0716+714, the long-term period of variation is 3.3 yr which is consistent with the result of Raiter et al. (2003).

    • Broad Band Spectral Index TeV Blazars Detected by Fermi LAT

      Yong Juan Cha Xiong Zhang

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      We collected the radio, K-band, optical, X-ray, and 𝛾-ray data for 35 TeV blazars detected by Fermi LAT and studied the possible correlation between different broad band spectral indices (𝛼r.o, 𝛼r.x, 𝛼ir.o, 𝛼ir.x, 𝛼o.𝛾, 𝛼x.𝛾) in all states (average/high/low). Based on our results, we suggested that the seed photons of the 𝛾-ray drive from the synchrotron radiation themselves.

    • Relation between X-Ray and 𝛾-Ray Emissions for Fermi Blazars

      Bijun Li Xiong Zhang

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      Using 𝛾-ray band data detected by Fermi Large Area Telescope (LAT) and X-ray band data for 78 blazars, we find a medium correlation between X-ray and 𝛾-ray fluxes in the average state. A medium anticorrelation is also found between X-ray (1 KeV) mean spectral index 𝛼𝑥 and 𝛾-ray mean spectral index 𝛼𝛾 for blazars. Our results suggest that the most likely radiation mechanism for the high energy 𝛾-ray would be SSC. And that the 𝛾-ray emission mechanism may be somewhat different for BL Lacs and FSRQs.

    • Debeamed Sequence of LBAS Blazars

      Bangrong Huang Xiong Zhang Dingrong Xiong Haojin Zhang

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      We have collected a sample of 71 𝛾-ray blazars selected from the Fermi LAT Bright AGN Sample (LBAS). The correlation between synchrotron peak luminosities 𝐿p and synchrotron peak frequencies 𝑣p have been studied and there is a weak negative correlation. But after correcting the effect of redshift and Doppler boosting, the relation between intrinsic 𝐿'p and 𝑣'p show significant positive correlation.

    • Broad-Band Spectral Indices Variability of BL Lacertae by Wavelet Method

      Hao-Jing Zhang Jing-Ming Bai Yu-Ying Bao Xiong Zhang

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      BL Lacertae is one of the famous AGN that shows convincing evidence to support periodic variability. We compile R-band data and radio 22 GHz database from the available literature to build the light curves and to calculate broad-band spectral indices. This paper employs the wavelet periodic estimation method. The analysis results indicate that the most possible period is 7.02–7.36 yr in the selected wave-bands. The broad-band spectral indices have a possible period of 4.11 yr as a half value in selected wave-bands. The results confirm that the variability period in the radio 22 GHz is in agreement with the optical R band of about 7.01 yr, as also mentioned in other literatures.

  • 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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