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arXiv · 1701.04454

Gamma-ray and Optical Oscillations of 0716+714, MRK 421, and BL Lac

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

We examine the 2008-2016 $\gamma$-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. Considering previous literature results, possibly related $\gamma$-ray and optical periodicities of about one year time scale are proposed in 4 bright $\gamma$-ray blazars out of the 10 examined in detail. Comparing with results from periodicity search of optical archives of quasars, the presence of quasi-periodicities in blazars might 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.

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A. Sandrinelli, S. Covino, A. Treves, E. Lindfors, C. M. Raiteri, K. Nilsson, L. O. Takalo, R. Reinthal, A. Berdyugin, V. Fallah Ramazani, V. Kadenius, T. Tuominen, P. Kehusmaa, R. Bachev, A. Strigachev. 2017-01-16. Gamma-ray and Optical Oscillations of 0716+714, MRK 421, and BL Lac. https://doi.org/10.1051/0004-6361%2F201630288

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