The connection between the giant optical outbursts of the flat spectrum radio quasars and the black hole precession

Flat Spectrum Radio Quasars (FSRQ) are a part of the blazar family, which in addition to the dominated nonthermal jet emission shows signatures, normally associated with the presence of a standard thin accretion disk, such like thermal continuum and broad emission lines. Furthermore, there is emerging evidence that the FSRQ are more likely to exhibit giant outbursts in the optical, with amplitudes reaching sometimes up to five magnitudes, compared to their quiescent state. We give examples, compiled from the literature and public archives in support of this statement. The most promising mechanism to account for such outbursts appears to be the changing Doppler factor (orientation with respect to the line of sights) of the jet. We attribute such orientation changes of the jet to the presence of misaligned thin accretion disk, leading to a black hole/accretion disk precession. Such a scheme can explain why FSRQ tend to produce large outbursts while other blazar types do not.