Correlation between Brightness Variability and Spectral Index Variability for Fermi Blazars  

作　　者：Wen-Xin Yang Hu-Bing Xiao Hong-Guang Wang Jiang-He Yang Zhi-Yuan Pei De-Xiang Wu Yu-Hai Yuan Jun-Hui Fan 

机构地区：[1]Center for Astrophysics,Guangzhou University,Guangzhou 510006,China [2]Astronomy Science and Technology Research Laboratory of Department of Education of Guangdong Province,Guangzhou 510006,China [3]Key Laboratory for Astronomical Observation and Technology of Guangzhou,Guangzhou 510006,China [4]Shanghai Key Lab for Astrophysics,Shanghai Normal University,Shanghai 200234,China [5]Department of Physics and Electronics Science,Hunan University of Arts and Science,Changde 415000,China

出　　处：《Research in Astronomy and Astrophysics》2022年第8期23-33,共11页天文和天体物理学研究（英文版）

基　　金：the National Natural Science Foundation of China(NSFC U2031201,11733001,U2031112,12133004 and 12103012);Guangdong Major Project of Basic and Applied Basic Research(Grant No.2019B030302001);the science research grants from the China Manned Space Project with NO.CMSCSST-2021-A06;the supports for Astrophysics Key Subjects of Guangdong Province and Guangzhou City;supported by Guangzhou University(YM2020001)。

摘　　要：In this work,theγ-ray photon flux,photon spectral index(α_(ph)),variability index(log V.I.),and the synchrotron peak frequency(log v_(p))are compiled for 851 common blazars from the 3 FGL and 4 FGL catalogs and Fan et al.to investigate variability properties for Fermi blazars.Our calculations and analyses reach following results:(1)the averaged luminosity,spectral index,and variability index of FSRQs are higher than those of BL Lacs for the whole sample.(2)It is found that the spectral index variation is closely anti-correlated with the luminosity variation implying that the spectrum becomes harder when the source becomes brighter in theγ-ray band.(3)Positive correlations are found between the photon spectral index and bothγ-ray luminosity and variability index(log V.I.)for the whole sample,but anti-correlations are found in the two correlations for FSRQs.For BL Lac subclass,there is a marginal anti-correlation between the photon spectral index and bothγ-ray luminosity,and a positive correlation between the photon spectral index and the variability index(log V.I.).We think those two positive correlations found for the whole sample are apparent.(4)We adopted the SVM machine learning method to separate BL Lacs and FSRQs in theα_(ph)versus log L_(γ)andα_(ph)versus log V.I.plots and proposed that a BCU is an FSRQ candidate if it satisfies log V.I.>-10.119 a+24.855,orα_(ph)>-0.048 log L_(γ)+4.498,otherwise,it is a BL Lac candidate.Our classification results are quite consistent with those by Kang et al(2019).

关 键 词：(galaxies:)BL Lacertae objects:general (galaxies:)quasars:general galaxies:active 

分 类 号：P152[天文地球—天文学]