Quasi-periodicities of BL Lacertae objects

Journal
Date Issued
2018
Author(s)
Sandrinelli, A.
•
•
Treves, A.
•
Holgado, A. M.
•
Sesana, A.
•
Lindfors, E.
•
Ramazani, V. F.
DOI
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.
Volume
615
Start page
A118
Uri
Url
Issn Identifier
0004-6361
Ads BibCode
2018A&A...615A.118S
Rights
open.access
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