Abstract
We analyse the light curve in the R band of the blazar OJ287, gathered during the 2015/2016 observing season. We did a search for quasi-periodic oscillations (QPOs) using several methods over a wide range of timescales. No statistically significant periods were found in the high-frequency domain both in the ground-based data and in Kepler observations. In the longer-period domain, the Lomb–Scargle periodogram revealed several peaks above the 99% significance level. The longest one—about 95 days—corresponds to the innermost stable circular orbit (ISCO) period of the more massive black hole. The 43-day period could be an alias, or it can be attributed to accretion in the form of a two-armed spiral wave.
Highlights
OJ287 is the only blazar known to exhibit certain quasi-periodic variability in its light curve, with a rough period of 12 years
We found no stable periods in the OJ287 photometric data over the entire 2015/2016 season
The 95-day peak in the power spectrum is close to the period for the more-massive BH innermost stable circular orbit (ISCO), while the 43-day peak is half of this value
Summary
Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, Perugia I-06123, Italy. Astrophysics Research Center and Ulupinar Observatory, Canakkale Onsekiz Mart University, Canakkale TR-17100, Turkey. Faculty of Electrical Engineering, Czech Technical University, Prague 74864, Czech Republic. INAF—Osservatorio Astronomico di Roma, via Frascati 33, Monteporzio Catone I-00040, Italy.
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