Dr. Suvendu Rakshit

Active galaxies are believed to be powered by the accretion of matter onto supermassive black holes. Measuring the masses and investigating the dynamics within the sub-parsec region of active galactic nuclei (AGN) remains challenging due to the need for high spatial resolution. Long-term spectro-photometric monitoring has been a crucial tool for probing the central engine, determining the linear size of the broad-line region (BLR), and estimating black hole masses. Concurrently, recent advances in optical spectro-interferometry have provided an independent method to measure black hole masses by determining the angular size of the BLR. By combining the linear size obtained from spectro-photometric studies with angular diameter measurements from optical interferometry, we can estimate distances to AGN across the Universe. In this talk, I will summarize the results of extensive spectro-photometric monitoring programs conducted over several years, highlight the latest findings from optical interferometric observations, and discuss their implications for distance measurements to AGN.