Toward a Real-time Transient Alert System for Passive Monitoring of Stellar Fields

Abstract We introduce VarWatch: a pipeline aimed at identifying variable stars and transient events during real-time observations with a co-mounted secondary telescope. VarWatch detects signals that change on timescales of minutes to hours, including flares, eclipsing binaries, pulsating stars, and supernovae. The algorithm utilizes optimal image subtraction for new object detection coupled with differential photometry to extract z -scores and excess variance, generates alerts for astronomers, and returns light curves for stars in real-time. We perform several validation tests on the pipeline, ensuring kernel recovery, astrometric precision, and sigma-clipping accuracy.