Quasiperiodic γ-Ray Modulations in the Blazars PKS 2155-83 and PKS 2255-282
While there has been an increase in interest in the possibility of quasiperiodic oscillations (QPOs) in blazars, the search has hitherto been restricted to sources with well-sampled light curves. Objects with light curves that include gaps have been, to our knowledge, overlooked. Here, we study two...
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2024-01-01
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| author | M. A. Hashad Amr A. EL-Zant Y. Abdou H. M. Badran |
| author_facet | M. A. Hashad Amr A. EL-Zant Y. Abdou H. M. Badran |
| author_sort | M. A. Hashad |
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| description | While there has been an increase in interest in the possibility of quasiperiodic oscillations (QPOs) in blazars, the search has hitherto been restricted to sources with well-sampled light curves. Objects with light curves that include gaps have been, to our knowledge, overlooked. Here, we study two such curves, which have the interesting feature of pertaining to relatively high-redshift blazars—FSRQs, PKS 2155-83, and PKS 2255-282—observed by the Fermi Large Area Telescope. Their redshifts border the “cosmic noon” era of galaxy formation and merging, and their light curves exhibit a distinctive pattern of repetitive high and low (gap dominant) states for 15.6 yr. To accommodate for the gaps in the curves, data are integrated over extended time intervals of 1 month and 2 months. The resulting curves were also examined using methods suitable for sparsely sampled data. This investigation of PKS 2155-83 and PKS 2255-282 suggests QPOs with periods of 4.69 ± 0.79 yr (3 σ ) and 6.82 ± 2.25 yr (2.8 σ ), respectively. The probability density functions of the blazars’ fluxes, along with the correlation between their flux and spectral index, were also analyzed. Given the epochs in which the objects are observed, the plausibility of a binary black hole scenario as an origin of the apparent periodicity was examined. We estimated the prospective parameters of such a system using a simple geometric model. The total masses were estimated and found to be consistent, in principle, with independent (dynamical) measurements of the central black hole masses in the two host galaxies. |
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| language | English |
| publishDate | 2024-01-01 |
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| spelling | doaj-art-440a0812bc10405f95bb0a03e5ed6fa32025-08-20T01:47:21ZengIOP PublishingThe Astrophysical Journal1538-43572024-01-01975216410.3847/1538-4357/ad7a6eQuasiperiodic γ-Ray Modulations in the Blazars PKS 2155-83 and PKS 2255-282M. A. Hashad0Amr A. EL-Zant1Y. Abdou2H. M. Badran3Department of Basic Science, Modern Academy for Engineering and Technology , Elmokattam 11439, Egypt ; Mohamed.Hashad@bue.edu.eg; Centre for Theoretical Physics, The British University in Egypt , Sherouk City, 11837, Cairo, EgyptCentre for Theoretical Physics, The British University in Egypt , Sherouk City, 11837, Cairo, EgyptPhysics Department, Faculty of Science, Tanta University , Tanta, 31527, Gharbia, EgyptPhysics Department, Faculty of Science, Tanta University , Tanta, 31527, Gharbia, EgyptWhile there has been an increase in interest in the possibility of quasiperiodic oscillations (QPOs) in blazars, the search has hitherto been restricted to sources with well-sampled light curves. Objects with light curves that include gaps have been, to our knowledge, overlooked. Here, we study two such curves, which have the interesting feature of pertaining to relatively high-redshift blazars—FSRQs, PKS 2155-83, and PKS 2255-282—observed by the Fermi Large Area Telescope. Their redshifts border the “cosmic noon” era of galaxy formation and merging, and their light curves exhibit a distinctive pattern of repetitive high and low (gap dominant) states for 15.6 yr. To accommodate for the gaps in the curves, data are integrated over extended time intervals of 1 month and 2 months. The resulting curves were also examined using methods suitable for sparsely sampled data. This investigation of PKS 2155-83 and PKS 2255-282 suggests QPOs with periods of 4.69 ± 0.79 yr (3 σ ) and 6.82 ± 2.25 yr (2.8 σ ), respectively. The probability density functions of the blazars’ fluxes, along with the correlation between their flux and spectral index, were also analyzed. Given the epochs in which the objects are observed, the plausibility of a binary black hole scenario as an origin of the apparent periodicity was examined. We estimated the prospective parameters of such a system using a simple geometric model. The total masses were estimated and found to be consistent, in principle, with independent (dynamical) measurements of the central black hole masses in the two host galaxies.https://doi.org/10.3847/1538-4357/ad7a6eActive galactic nucleiGamma-ray astronomyTime series analysisNon-thermal radiation sourcesGalaxy mergersBlazars |
| spellingShingle | M. A. Hashad Amr A. EL-Zant Y. Abdou H. M. Badran Quasiperiodic γ-Ray Modulations in the Blazars PKS 2155-83 and PKS 2255-282 The Astrophysical Journal Active galactic nuclei Gamma-ray astronomy Time series analysis Non-thermal radiation sources Galaxy mergers Blazars |
| title | Quasiperiodic γ-Ray Modulations in the Blazars PKS 2155-83 and PKS 2255-282 |
| title_full | Quasiperiodic γ-Ray Modulations in the Blazars PKS 2155-83 and PKS 2255-282 |
| title_fullStr | Quasiperiodic γ-Ray Modulations in the Blazars PKS 2155-83 and PKS 2255-282 |
| title_full_unstemmed | Quasiperiodic γ-Ray Modulations in the Blazars PKS 2155-83 and PKS 2255-282 |
| title_short | Quasiperiodic γ-Ray Modulations in the Blazars PKS 2155-83 and PKS 2255-282 |
| title_sort | quasiperiodic γ ray modulations in the blazars pks 2155 83 and pks 2255 282 |
| topic | Active galactic nuclei Gamma-ray astronomy Time series analysis Non-thermal radiation sources Galaxy mergers Blazars |
| url | https://doi.org/10.3847/1538-4357/ad7a6e |
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