Rosanne Di Stefano

M51-ULS1b, the first candidate planet in another galaxy, was discovered because it transited a bright X-ray source in the Whirlpool galaxy, M51.  Searches for other distant planets provide powerful reasons to study the short-time-scale behavior of X-ray sources. Equally important are other classes of short-duration events, including X-ray flares which may be due to either system variability or binary self lensing.  I will discuss some of the implications of the discovery of M51-ULS1b, and describe an exciting ongoing project in which we are analyzing the X-ray light curves of sources in more than 300 galaxies.