The Swift Plan for O4: Catching NS-NS Mergers on the Fly

Swift is currently the only mission that can localize a short GRB to < 3 arc-minute resolution, or better. In O4 we plan to use Swift as a discovery tool for the next NS-NS merger that is detected in Gravitational Waves by LIGO/Virgo/KAGRA in the upcoming O4 run, and rapidly report that location with arc-minute or better localization. Although Swift’s Burst Alert Telescope (BAT) may be lucky enough to passively detect a GW related event, given the likely low rate of these events and BAT triggering only covering 1/6th of the sky, we need to be proactive to increase the chances of this happening. Here we present the news evolutions of the Swift telescope that will allow us to deliver this result, using new initiatives. Firstly, we talk about the Gamma-ray Urgent Archiver for Novel Opportunities (GUANO), a system that proactively dumps otherwise lost BAT event data, allowing us to provide a sensitive search for EM emission both inside and outside the FOV of the BAT, with localization capabilities in both cases. We discuss the improvements to Swift commanding that allow commands to be sent in real-time, allowing us to not only perform realtime searches for counterparts, but also allows us to realign the spacecraft to more favorably align BAT with the location of the merger, based on early warning alerts that are releases by LVK prior to the merger. We also present results from O3 from Swift for afterglow searches.