• J. H. Yang

      Articles written in Journal of Astrophysics and Astronomy

    • The Correlation between 𝛾-Ray and Radio Emissions for the Fermi Blazars

      J. H. Yang J. H. Fan

      More Details Abstract Fulltext PDF

      Based upon the Fermi blazars sample, the radio and 𝛾-ray emissions are compiled for a sample of 74 𝛾-ray loud blazars to calculate the radio to 𝛾-ray effective spectrum index 𝛼R𝛾 . The correlations between 𝛼R𝛾 and 𝛾-ray luminosity, and between radio and 𝛾-ray luminosity are also investigated.

    • Relationship among FR-I, FR-II(Q) and FR-II(G) Radio Galaxies

      R. S. Yang J. H. Yang Y. X. Wang J. H. Fan

      More Details Abstract Fulltext PDF

      Based on a sample of radio galaxies, the effective spectrum index 𝛼RO (178 MHz to 0.54 𝜇m), the radio and the V-band optical luminosities are investigated for FR-I, FR-II(G) and FR-II(Q).

    • Dependence of Core and Extended Flux on Core Dominance Parameter for Radio Sources

      J. J. Nie J. H. Yang

      More Details Abstract Fulltext PDF

      Based on two extragalactic radio source samples, the core dominance parameter is calculated, and the correlations between the core/extended flux density and core dominance parameter are investigated. When the core dominance parameter is lower than unity, it is linearly correlated with the core flux density, but it is not correlated with the extended flux density. When the core dominance parameter is higher than unity, it is not correlated with the core flux density, but it is linearly correlated with the extended flux density. Therefore, there are different results from different samples. The results can be explained using a relativistic beaming model.

    • Relativistic Beaming Effect in Fermi Blazars

      J. H. Fan D. Bastieri J. H. Yang Y. Liu D. X. Wu S. H. Li

      More Details Abstract Fulltext PDF

      The most identified sources observed by Fermi/LAT are blazars, based on which we can investigate the emission mechanisms and beaming effect in the 𝛾-ray bands for blazars. Here, we used the compiled around 450 Fermi blazars with the available X-ray observations to estimate their Doppler factors and compared them with the integral 𝛾-ray luminosity in the range of 1–100 GeV. It is interesting that the integral 𝛾-ray luminosity is closely correlated with the estimated Doppler factor, log 𝑣𝛾 𝐿𝑣𝛾 = (2.95 ± 0.09) log 𝛿 + 43.59 ± 0.08 for the whole sample. When the dependence of the correlation between them and the X-ray luminosity is removed, the correlation is still strong, which suggests that the 𝛾-ray emissions are strongly beamed.

    • Spectral Index Changes with Brightness for 𝛾-Ray Loud Blazars

      J. H. Yang R. S. Yang J. J. Nie J. H. Fan

      More Details Abstract Fulltext PDF

      Based on Fermi 1FGL and 2FGL data, a sample of 572 𝛾-ray loud blazars are selected, in which each source has both 𝛾-ray flux and spectral index in 1FGL and 2FGL, respectively. Theoretic relation of spectral index changes depending on 𝛾-ray brightness is obtained. The correlations between the ratio of 𝛾-ray flux densities and the differences of the 𝛾-ray spectral indices are discussed for the three subclasses of HBL, LBL and FSRQs. Results show that the ratio is related with the differences for the three subclasses. It is consistent with the theoretical result and it indicates that the spectrum becomes flat as the source brightens in the 𝛾-ray band.

    • Effective Spectral Indices of Core and Extended Emissions for Radio Sources

      R. S. Yang J. H. Yang J. J. Nie

      More Details Abstract Fulltext PDF

      From some available literatures, a sample of 393 radio sources is selected. The core and extended spectral indices are calculated. Results show that the core spectral index is different from the extended spectral index with the middle values approximately being 0 and 0.8 respectively.

    • Relation of Core Dominance Parameter and Extended Spectral Index for Radio Sources

      J. H. Yang J. J. Nie J. H. Fan

      More Details Abstract Fulltext PDF

      The correlations between differences of two core dominance parameters and core/extended spectral index are investigated. The extended spectral index is associated with the differences very well, while there is a weak relationship between core spectral index and the differences. The average core spectral index tends to be a `constant’ ∼ 0.0.

  • 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

© 2017-2019 Indian Academy of Sciences, Bengaluru.