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The gamma-ray spectral index changes for blazars

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Abstract

Based upon Fermi 1FGL and EGRET 3EG samples, a sample including 79 blazars (53 FSRQs, 26 BL Lacs) is presented. It is investigated that the correlations between the ratio of EGRET to Fermi blazars γ-ray flux densities and the spectral index differ for EGRET to Fermi blazars for three subclasses of high-frequency peaked BL Lacertae objects-HBL, low-frequency peaked BL Lacertae objects-LBL, and flat spectrum radio quasars-FSRQs. There is a consistent relationship between the ratio of the two γ-ray flux densities and the spectral index difference for the three subclasses. It suggests that the spectrum changed with the source brightness in the gamma-ray band. Both the spectral index difference and the correlation slopes follow a continuous sequence from FSRQs to LBLs to HBLs, which is consistent with the noted blazar sequence.

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Authors and Affiliations

  1. Department of Physics and Electronics Science, Hunan University of Arts and Science, Changde, 415000, China

    JiangHe Yang, JianJun Nie & RuShu Yang

  2. Center for Astrophysics, Guangzhou University, Guangzhou, 510405, China

    JiangHe Yang & JunHui Fan

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  1. JiangHe Yang
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  2. JunHui Fan
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Yang, J., Fan, J., Nie, J. et al. The gamma-ray spectral index changes for blazars. Sci. China Phys. Mech. Astron. 55, 2179–2185 (2012). https://doi.org/10.1007/s11433-012-4901-8

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