Gamma-ray and optical oscillations of 0716+714, MRK 421, and BL Lacertae

Author： Sandrinelli A. Covino S. Treves A. Lindfors E. Raiteri C. M. Nilsson K. Takalo L. O. Reinthal R. Berdyugin A. Fallah Ramazani V. Kadenius V. Tuominen T. Kehusmaa P. Bachev R. Strigachev A.

Publisher： Edp Sciences

E-ISSN： 1432-0746|600|issue|A132-A132

ISSN： 0004-6361

Source： Astronomy & Astrophysics, Vol.600, Iss.issue, 2017-04, pp. : A132-A132

Disclaimer: Any content in publications that violate the sovereignty, the constitution or regulations of the PRC is not accepted or approved by CNPIEC.

Previous Menu Next

Abstract

We 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.