Presentation #208.02 in the session The Proposed STAR-X Explorer Mission: Opportunities for the HEAD Community to Explore the Fast, Furious and Forming Universe with Simultaneous UV and X-ray Observations.
STAR-X is a powerful X-ray and UV time-domain observatory with rapid-response (<2 hour) ToO capability. I will motivate the harmonious design and observing strategy that enables STAR-X to capture populations of rare and brief transient events while simultaneously accumulating deep surveys to discover populations of rare and faint objects. STAR-X does this by operating in several modes. First, 60% of its time is spent in daily and weekly cadenced surveys to catch serendipitous transients and monitor variable sources. Upon detecting a transient onboard, STAR-X will alert the community within 5-10 minutes. These surveys will also build up deep, extremely rich data sets with high-z AGNs, rare galaxy types, faint, fast X-ray transients, and more. Secondly, STAR-X will perform rapid-response ToOs in response to high-value transients (supernova shock breakouts and searches for gravitational wave counterparts) and reserve more than 1 Ms of time for community ToO requests (typical response of about a day). The X-ray+UV combination will yield the most information about the rapid, early decay of such transients and what makes them. Finally, STAR-X will execute pointed surveys of samples of targets, including low-mass stars, high-z galaxy clusters, and nearby galaxies to understand the impact of flares on exoatmospheres, the formation of galaxy clusters, and the genesis of compact object populations.