Multiwavelength cross-correlations in blazars

In this work, we study radio, optical, and {gamma}-ray light curves of 145 bright blazars spanning up to 8 yr, to probe the flaring activity and interband correlations. Of these, 105 show >1{sigma} correlations between one or more wavebands, 26 of which have a >3{sigma} correlation in at least one wavelength pair, as measured by the discrete correlation function.

The most common and strongest correlations are found between the optical and {gamma}-ray bands, with fluctuations simultaneous within our ~30d resolution. The radio response is usually substantially delayed with respect to the other wavelengths with median time lags of ~100-160d. A systematic flare identification via Bayesian block analysis provides us with a first uniform sample of flares in the three bands, allowing us to characterize the relative rates of multiband and 'orphan' flares.