A dual-frequency, multiyear monitoring program of compact radio sources

We present light curves for 149 sources monitored with the Green Bank Inter ferometer. The light curves are at two radio frequencies (approximately 2.5 and 8.2 GHz) and range from 3 to 15 yr in length, covering the interval 19 79-1996, and have a typical sampling of one flux density measurement every 2 days. We have used these light curves to conduct various variability anal ysis (rms flux density variations and autoregressive, integrated, moving av erage modeling) of these sources. We find suggestive though not unambiguous evidence that these sources have a common, broadband mechanism for intrins ic variations, in agreement with previous studies of a subset of these sour ces. We also find that the sources generally display a short-term variabili ty (similar to 10 days) that arises from radio-wave scattering in an extend ed medium. These conclusions extend those of Fiedler et al., who used a sub sample of these data. The primary motivation for this monitoring program wa s the identification of extreme scattering events (ESEs). In an effort to i dentify ESEs in a systematic manner, we have taken the wavelet transform of the light curves. We find 15 events in the light curves of 12 sources that we classify as probable ESEs. However, we also find that five ESEs previou sly identified from these data do not survive our wavelet selection criteri a. Future identification of ESEs will probably continue to rely on both vis ual and systematic methods. Instructions for obtaining the data are also pr esented.