LIGO-Virgo-KAGRA data products in the fourth observing run

Kilonova observations are crucial for our understanding of the neutron star equation of state and r-process nucleosynthesis. In compact binary mergers with at least one neutron star, the equation of state influences how much matter is ejected from the merger, and this neutron-rich ejecta is expected to be a site of r-process nucleosynthesis. Kilonova are faint and short lived, however, and finding them is no easy task. Electromagnetic follow-up of gravitational wave observations of mergers, like the combined detection of GW170817 and AT 2017gfo, give us our best chance at detecting kilonovae in the near future. As LIGO's fourth observing run approaches, we present the techniques and data products that will be used to assist follow-up of electromagnetic counterparts to gravitational wave detections, and the ongoing validation of these products in real-time replay through the Mock Data Challenge. We cover both public data products, as well as those in development, such as kilonova light curve predictions.