J. H. Yang
Articles written in Journal of Astrophysics and Astronomy
Volume 32 Issue 1-2 March 2011 pp 203-205 Part 4. Emission Models and Theory
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.
Volume 32 Issue 1-2 March 2011 pp 307-308 Part 7. Other Topics
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).
Volume 35 Issue 3 September 2014 pp 227-230 Posters
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.
Volume 35 Issue 3 September 2014 pp 231-235 Part II: Blazar Observations in Infrared and Optical
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.
Volume 35 Issue 3 September 2014 pp 401-404 Posters
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.
Volume 35 Issue 3 September 2014 pp 405-406 Posters
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.
Volume 35 Issue 3 September 2014 pp 487-488 Posters
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.
Volume 40 | Issue 6
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