Sandrinelli, A.A.SandrinelliCOVINO, StefanoStefanoCOVINOTreves, A.A.TrevesLindfors, E.E.LindforsRAITERI, Claudia MariaClaudia MariaRAITERINilsson, K.K.NilssonTakalo, L. O.L. O.TakaloReinthal, R.R.ReinthalBerdyugin, A.A.BerdyuginFallah Ramazani, V.V.Fallah RamazaniKadenius, V.V.KadeniusTuominen, T.T.TuominenKehusmaa, P.P.KehusmaaBachev, R.R.BachevStrigachev, A.A.Strigachev2020-08-272020-08-2720170004-6361http://hdl.handle.net/20.500.12386/26884We examine the 2008-2016 γ-ray and optical light curves of three bright BL Lac objects, 0716+714, MRK 421, BL Lac, which exhibit large structured variability. We searched for periodicities by using a fully Bayesian approach. For two out of three sources investigated, no significant periodic variability was found. In the case of BL Lac, we detected a periodicity of 680 days. Although the signal related to this is modest, the coincidence of the periods in both gamma and optical bands is indicative of a physical relevance. Taking into consideration previous literature results, possibly related γ-ray and optical periodicities of about one year time scale are proposed in four bright γ-ray blazars out of the ten examined in detail. Compared with results from periodicity search of optical archives of quasars, the presence of quasi-periodicities in blazars may be more frequent by a large factor. This suggests the intriguing possibility that the basic conditions for their observability are related to the relativistic jet in the observer direction, but the overall picture remains uncertain.STAMPAenArticle10.1051/0004-6361/2016302882-s2.0-85017501641000400754000141https://www.aanda.org/articles/aa/abs/2017/04/aa30288-16/aa30288-16.html2017A&A...600A.132SFIS/05 - ASTRONOMIA E ASTROFISICAERC sectors::Physical Sciences and Engineering::PE9 Universe sciences: astro-physics/chemistry/biology; solar systems; stellar, galactic and extragalactic astronomy, planetary systems, cosmology, space science, instrumentation::PE9_10 High energy and particle astronomy – X-rays, cosmic rays, gamma rays, neutrinos