Long-term variability of radio-bright BL Lacertae objects
  Radio-bright BL Lacertae objects (BLOs) are typically variable and exhibit
prominent flaring. We use a sample of 24 BLOs to get a clear idea of their
flaring behavior and to find possible commonalities in their variability
patterns. Our goal was to compare the results given by computational time
scales and the observed variability parameters determined directly from the
flux curves. Also, we wanted to find out if the BLO flares adhere to the
generalized shock model. We use long-term monitoring data from 4.8, 8, 14.5,
22, 37, 90 and 230 GHz. The structure function, discrete correlation function
and Lomb-Scargle periodogram time scales, calculated in a previous study, are
analyzed in more detail. We determine flare durations, rise and decay times,
absolute and relative peak fluxes from the monitoring data. We find that BLOs
demonstrate a wide range of variability behavior. BLOs include sources with
fast and strong variability, such as OJ 287, PKS 1749+096 and BL Lac, but also
sources with more rolling fluctuations like PKS 0735+178. The most extreme
flares can last for up to 13 years or have peak fluxes of approximately 12 Jy
in the observer's frame. When the Doppler boosting effect is taken into
account, the peak flux of a flare does not depend on the duration of the flare.
A rough analysis of the time lags and peak flux evolution indicates that BLO
flares in the mm - cm wavelengths are high-peaking, i.e., are in the adiabatic
stage. Thus, the results concur with the generalized shock model.
