Effective spectral index properties for Fermi blazars

• 来源期刊: 中国科学:物理学 力学 天文学（英文版）
• 年，卷（期）: 2018,（5）
• 页码范围: 46-52
• 页数: 7页
• 语种: 英文

摘要

Blazars are a special subclass of active galactic nuclei with extreme observation properties.This subclass can be divided into two further subclasses of fiat spectrum radio quasars (FSRQs) and BL Lacertae objects (BL Lacs) according to their emission line features.To compare the spectral properties of FSRQs and BL Lacs,the 1.4 GHz radio,optical R-band,1 keY X-ray,and 1 GeV γ-ray flux densities for 1108 Fermi blazars are calculated to discuss the properties of the six effective spectral indices of radio to optical (αRO),radio to X-ray (αRX),radio to γ ray (αRγ),optical to X-ray (αOX),optical to γ ray (αOγ),and X-ray to γ ray (αXγ).The main results are as follows:For the averaged effective spectral indices,(αOX) ＞ (αOγ) ＞ (αXγ) ＞ (αRγ) ＞ (αRX) ＞ (αRO) for samples of whole blazars and BL Lacs;(αXγ) ≈ (αRγ) ≈ (αRX) for FSRQs and low-frequency-peaked BL Lacs (LBLs);and (αOX) ≈ (αOγ) ≈ (αXγ)for high-synchrotron-frequency-peaked BL Lacs (HBLs).The distributions of the effective spectral indices involving optical emission (αRO,αOX,and αOγ) for LBLs are different from those for FSRQs,but if the effective spectral index does not involve optical emission (αRX,αRγ,and αXγ),the distributions for LBLs and FSRQs almost come from the same parent population.X-ray emissions from blazars include both synchrotron and inverse Compton (IC) components;the IC component for FSRQs and LBLs accounts for a larger proportion than that for HBLs;and the radiation mechanism for LBLs is similar to that for FSRQs,but the radiation mechanism for HBLs is different from that for both FSRQs and LBLs in X-ray bands.The tendency of αRγ decreasing from LBLs to HBLs suggests that the synchrotron self-Compton model explains the main process for highly energetic γ rays in BL Lacs.