Abstract:
We perform correlation and periodicity search analyses on long-term multiband light curves of the flat-spectrum
radio quasar PKS 1510−089 observed by the space-based Fermi-Large Area Telescope in γ-rays, the SMARTS
and Steward Observatory telescopes in optical and near-infrared (NIR), and the 13.7 m radio telescope in
Metsähovi Radio Observatory between 2008 and 2018. The z-transform discrete correlation function method is
applied to study the correlation and possible time lags among these multiband light curves. Among all pairs of
wavelengths, the γ-ray versus optical/NIR and optical versus NIR correlations show zero time lags; however, both
the γ-ray and optical/NIR emissions precede the radio radiation. The generalized Lomb–Scargle periodogram,
weighted wavelet z-transform, and REDFIT techniques are employed to investigate the unresolved core emission–
dominated 37 GHz light curve and yield evidence for a quasi period around 1540 days, although given the length
of the whole data set it cannot be claimed to be significant. We also investigate the optical/NIR color variability
and find that this source shows a simple redder-when-brighter behavior over time, even in the low-flux state.
