The Spectral Variation Behavior of Fermi-LAT Blazars
In this study, we analyze the ∼16 yr Fermi-Large Area Telescope data of 160 blazars consisting of 92 flat-spectrum radio quasars (FSRQs), 64 BL Lacertae (BL Lac)–type objects, and 4 blazar-candidates-of-unknown-type objects, and investigate their spectral variation. By fitting a linear model ( y = ...
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IOP Publishing
2025-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/adc106 |
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| author | Junhao Deng Yunguo Jiang |
| author_facet | Junhao Deng Yunguo Jiang |
| author_sort | Junhao Deng |
| collection | DOAJ |
| description | In this study, we analyze the ∼16 yr Fermi-Large Area Telescope data of 160 blazars consisting of 92 flat-spectrum radio quasars (FSRQs), 64 BL Lacertae (BL Lac)–type objects, and 4 blazar-candidates-of-unknown-type objects, and investigate their spectral variation. By fitting a linear model ( y = kx + b ) to the monthly binned flux-index plots, we find that most of the FSRQs (∼89%) display a harder-when-brighter trend ( k > 0), while the majority of BL Lac–type objects (∼64%) exhibit a softer-when-brighter trend ( k < 0). By plotting their slope ( k ) versus their variability index and inverse Compton (IC) peak frequency, we find a moderate positive correlation between k and the variability index and a moderate negative correlation between k and the IC peak frequency, which we name as the gamma-ray variability sequence of blazars. Additionally, eight blazars may not follow the linear variation trend, particularly in PKS 0537-441, AP Librae, and PKS 1510-089. Additional very-high-energy gamma-ray emission components may be the cause of the nonlinear variation trend. |
| format | Article |
| id | doaj-art-a7937002fe2e4205b5f57ce0e8e2d500 |
| institution | OA Journals |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
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| series | The Astrophysical Journal |
| spelling | doaj-art-a7937002fe2e4205b5f57ce0e8e2d5002025-08-20T02:16:10ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-01983212810.3847/1538-4357/adc106The Spectral Variation Behavior of Fermi-LAT BlazarsJunhao Deng0https://orcid.org/0009-0007-1984-6603Yunguo Jiang1https://orcid.org/0000-0003-2679-0445Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, Institute of Space Sciences, Shandong University , Weihai 264209, People’s Republic of China ; jiangyg@sdu.edu.cn; School of Space Science and Technology, Shandong University , Weihai 264209, People’s Republic of ChinaShandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, Institute of Space Sciences, Shandong University , Weihai 264209, People’s Republic of China ; jiangyg@sdu.edu.cn; School of Space Science and Technology, Shandong University , Weihai 264209, People’s Republic of ChinaIn this study, we analyze the ∼16 yr Fermi-Large Area Telescope data of 160 blazars consisting of 92 flat-spectrum radio quasars (FSRQs), 64 BL Lacertae (BL Lac)–type objects, and 4 blazar-candidates-of-unknown-type objects, and investigate their spectral variation. By fitting a linear model ( y = kx + b ) to the monthly binned flux-index plots, we find that most of the FSRQs (∼89%) display a harder-when-brighter trend ( k > 0), while the majority of BL Lac–type objects (∼64%) exhibit a softer-when-brighter trend ( k < 0). By plotting their slope ( k ) versus their variability index and inverse Compton (IC) peak frequency, we find a moderate positive correlation between k and the variability index and a moderate negative correlation between k and the IC peak frequency, which we name as the gamma-ray variability sequence of blazars. Additionally, eight blazars may not follow the linear variation trend, particularly in PKS 0537-441, AP Librae, and PKS 1510-089. Additional very-high-energy gamma-ray emission components may be the cause of the nonlinear variation trend.https://doi.org/10.3847/1538-4357/adc106Blazars |
| spellingShingle | Junhao Deng Yunguo Jiang The Spectral Variation Behavior of Fermi-LAT Blazars The Astrophysical Journal Blazars |
| title | The Spectral Variation Behavior of Fermi-LAT Blazars |
| title_full | The Spectral Variation Behavior of Fermi-LAT Blazars |
| title_fullStr | The Spectral Variation Behavior of Fermi-LAT Blazars |
| title_full_unstemmed | The Spectral Variation Behavior of Fermi-LAT Blazars |
| title_short | The Spectral Variation Behavior of Fermi-LAT Blazars |
| title_sort | spectral variation behavior of fermi lat blazars |
| topic | Blazars |
| url | https://doi.org/10.3847/1538-4357/adc106 |
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