In a recent paper by Carina Fian et al., a set of intermediate band filters was used to monitor light fluctuations across the optical band from the low-redshift quasar, PG2130. The set of bands was carefully chosen so as to avoid prominent  broad emission lines that could lead to biased results. Light curves were obtained over several months’ duration with high cadence (see figure above), which allowed interband time-delays measurements that arise from the nature of the emission mechanism of the source. This is a first-of-its-kind interband time-delays measurement for a bright active galactic nuclei, and for this source. More information can be found here.