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http://hdl.handle.net/20.500.12386/27965
Titolo: | Quasi-periodicities of BL Lacertae objects | Autori: | Sandrinelli, A. COVINO, Stefano Treves, A. Holgado, A. M. Sesana, A. Lindfors, E. Ramazani, V. F. |
Data pubblicazione: | 2018 | Rivista: | ASTRONOMY & ASTROPHYSICS | Numero: | 615 | Da pagina:: | A118 | Abstract: | We review the reports of possible year-long quasi-periodicities of BL Lac objects in the γ-ray and optical bands, and present a homogeneous time analysis of the light curves of PKS2155-304, PG1553+113, and BL Lac. Based on results from a survey covering the entire Fermi γ-ray sky we have estimated the fraction of possible quasi-periodic BL Lac objects. We compared the cyclical behaviour in BL Lac objects with that derived from the search of possible optical periodicities in quasars, and find that at z ≲ 1 the cosmic density of quasi-periodic BL Lac objects is larger than that of quasi-periodic quasars. If the BL Lac quasi-periodicities were due to a supermassive binary black hole (SBBH) scenario, there could be a tension with the upper limits on the gravitational wave background measured by the pulsar timing array. The argument clearly indicates the difficulties of generally associating quasi-periodicities of BL Lac objects with SBBHs. | URI: | http://hdl.handle.net/20.500.12386/27965 | URL: | https://www.aanda.org/articles/aa/abs/2018/07/aa32550-17/aa32550-17.html | ISSN: | 0004-6361 | DOI: | 10.1051/0004-6361/201732550 | Bibcode ADS: | 2018A&A...615A.118S | Fulltext: | open |
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