When the darkness shines: the search for electromagnetic counterparts to gravitational wave events and its use as a probe of binary black hole formation*

The ever-growing catalog of gravitational wave events continues to be a valuable source of information for the field of astronomy, and is greatly enriched when supplemented with data from electromagnetic follow up campaigns, enabling identification of host environments and subsequently more precise measurements of cosmological parameters. While neutron star mergers remain the only gravitational wave events with a confirmed counterpart, several models have been proposed in which a binary black hole merger in the accretion disc of an active galactic nucleus could also lead to an observable luminous component. Although no such counterpart has been confirmed, several candidates have been proposed, and ongoing programs continue to look for others during the ongoing LIGO/Virgo/KAGRA observing run. I present updates from the Gravitational Wave Multi-Messenger Astronomy DECam Survey (GW-MMADS) team regarding our electromagnetic follow up efforts during O4. I also present our application of a Bayesian framework to the existing dataset of counterpart candidates for the first three gravitational wave observing runs to constrain parameters such as the binary black hole - active galactic nucleus association fraction.