Multifrequency observations of blazars. 5: Long-term millimeter, submillimeter, and infrared monitoring

Abstract

Multifrequency monitoring data are presented for 17 blazars between 375 and 22 GHz. These data are used to study the overall flaring behavior of blazars, and, in particular, to test predictions of shock models for the early phases of flare evolution. It is shown that time delays between light curves and flare amplitudes at different frequencies are in good agreement with existing shock models. Evidence is found for the flares in BL Lac objects to reach maximal development at lower frequency than those of optically violent variable quasars. On short timescales the variability behavior is complex, with 'flickering' over a range of amplitudes. Most objects that underwent a large outburst during the monitoring period show a flattening of the 375-150 GHz spectral slope with increasing 270 GHz flux.